Me n Mine Science x Ist Term

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PULLOUT WORKSHEETS

FOR CLASS XFirst Term

By

Vibha Arora Anju Sachdeva Sushma SardanaM.Sc., B.Ed. M.Sc., M.Ed. M.Sc., M.Ed.

Dept. of Physics Dept. of Chemistry Dept. of BiologyDelhi Public School Delhi Public School Delhi Public School

R. K. Puram, New Delhi R. K. Puram, New Delhi R. K. Puram, New Delhi

Me 'n' MineMe 'n' Mine

Science

data

New Stamp

– 2 –

CONTENTS

FIRST TERM

PHYSICS1. ELECTRICITY

Worksheets 1 to 18 ................................................................................................................................ 5–13

• Chapter Test...........................................................................................................................................13–14

2. MAGNETIC EFFECTS OF ELECTRIC CURRENT

Worksheets 23 to 27 ...........................................................................................................................15–18

• Chapter Test..................................................................................................................................................18

3. SOURCES OF ENERGY

Worksheets 31 to 37 ...........................................................................................................................19–24

• Chapter Test..................................................................................................................................................24

CHEMISTRY

4. CHEMICAL REACTIONS AND EQUATIONS

Worksheets 40 to 47 ...........................................................................................................................26–32

• Chapter Test...........................................................................................................................................32–33

5. ACIDS, BASES AND SALTS

Worksheets 52 to 64 ...........................................................................................................................34–41

• Chapter Test...........................................................................................................................................41–42

6. METALS AND NON-METALS

Worksheets 69 to 84 ...........................................................................................................................43–55

• Chapter Test...........................................................................................................................................55–56

BIOLOGY7. LIFE PROCESSES

Worksheets 89 to 107 .........................................................................................................................58–70

• Chapter Test...........................................................................................................................................70–71

8. CONTROL AND COORDINATION

Worksheets 113 to 120 .......................................................................................................................72–77

• Chapter Test..................................................................................................................................................77

PRACTICE PAPERS (I to V) ............................................................................................................. 79–102

SOLUTIONS TOPULLOUT WORKSHEETS

PHYSICS

E L E C T R I C I T Y 5

WORKSHEET-1

1. (a) 2. (c) 3. (b) 4. (c) 5. (b) 6. (b) 7. (b) 8. (b) 9. (b) 10. (a)11. (d) 12. (d) 13. (a) 14. (b) 15. (d) 16. (a) 17. (d) 18. (c) 19. (d) 20. (a)21. (d) 22. (a) 23. (b) 24. (b) 25. (a) 26. (d) 27. (a) 28. (b) 29. (a) 30. (a)

WORKSHEET-21. (c) 2. (a) 3. (a) 4. (a) 5. (a) 6. (b) 7. (a) 8. (d)9. A basic entity capable of independent existence. It is of two types + ve and ve. SI unit

coulomb.10. Net charge is ve.11. Whenever two charges q1 and q2 are separated by a distance r from their centres, there

exists a force of attraction or repulsion which is directly proportional to product of twocharges and inversely to square of distance between them.

F∝ 1 22

q q

r

F = 1 22

q qK

r.

12. F = 1 22

q qK

r=

9 19 19

6 29 10 1.6 10 1.6 10

(1 10 )

− −

−× × × × ×

× = 2304 × 1019 N.

13. It means work done in moving a unit positive charge between points A and B in that fieldis 3 J.

14. 1 volt = 1 joule/1 coulomb.Potential or potential difference.

15. Resistivity of a given material is a constant. Therefore, it is not affected by change in lengthof wire.

16. Least possible when three are in parallel = 1.03 Ω.Maximum possible when three are in series = 10 Ω.

17. 2 Ω.18. Because surface charges get removed and come to the surface.19. A bulb of 50 W became P ∝ R.20. 1 joule = 1 volt × 1 coulomb.

WORKSHEET-31. It is a closed path within which electrical current can flow.2. Resistance of a conductor increases with increase in temperature.3. SI unit for resistance is ohms, Ω.

SI unit for resistivity is ohm-metre, Ω m.

1 ELECTRICITY

6 XS C I E N C E

4.

5. As the temperature increases, resistance increases.∴ T2 > T1

∴ Resistance is V

=RI

.

6. Since Resistance = VI

∴ R1 > R2 > R3

Hence, R1 is maximum and R3 is minimum.7. Geyser has higher resistance and hence, draws more power. Therefore, light from bulb gets

dimmer for a moment.8. Tungsten is preferred because;

(a) It has high resistance, high melting point.(b) For some rise in temperature it gives more light.

9. (i) Electrical transmission line: Cu is preferred as it has low resistivity and is a goodconductor. Therefore, without lossing much of electricity in transmitting.

(ii) Electrical heating devices: Manganin is preferred due to high resistivity, being an alloyits resistance does not change with rise of temperature and works suitably with heatingeffect to produce maximum heat in least time.

10. Alloys are preferred because;(i) In alloys, resistance does not vary much with increase of temperature.

(ii) They do not get oxidised on heating.

WORKSHEET-4

1. In series circuit (i) as resistances are connected one after other. Therefore, effective resistanceis more, hence, current is less (ii) if one appliance is defective or not working in series otherswould also not work.

2. Electric circuit. It is a closed path within which electric current moves.Open electric circuit. In an open electric circuit, the electric current does not flow as there issome break in the path, i.e., either the key is open or some other end is not connected.Closed electric circuit. In this an electric current flows as the path is closed.

3. (a) It is a straight line passing through zero.(b) Slope of this graph at any point gives resistance of the circuit.

4. E = P × t = 1200 × 2060

= 0.4 units = 0.4 kWh


5. A parabolic or concave reflector throws heat radiations to maximum distance if the filamentis at the focus of that reflector.

6. R = ρ × lA

ρ =RA

l = 10 ×

− −× × ××

3 30.1 10 0.1 10227 1

= 3.14 × 107 Ω m.

7. As per Coulombs law F ∝ 1 22

q q

r.

So, if distance is doubled then force will reduce to 1

th4

its original value.

8. e = 1.6 × 1019 C, α = +2e = 3.2 × 1019 C, r = 1 × 106 m.

F = 1 22

q qK

r;

F = ( ) ( )

( )9 19 19

26

9 10 1.6 10 3.2 10

1 10

− −

−

× − × × ×

× = 4.6 × 1035 N.

9. I =nqt

10 × 10 3 =191.6 10

1n −× ×

⇒ n = 6.25 × 1016 = 6.25 × 1016 electron/sec.

10.R R

R2 1

1100

−×

= A1

l l

l2 1

1

100

×

∴ % increase = 25%Resistivity is a constant, therefore, it will not increase.

WORKSHEET-5

1. (a) P = V2/R∴ R = V2/P = (220)2/20 = 2420 Ω

(b) Energy = P × t = 20 × 10 = 200 Wh = 0.2 kWhNo. of units = 0.2 units daily.

2. Power input = 60 J/s, Power output = 7.5 J/s

Efficiency =7.5

×10060

= 12.5%.

3. Heat energy = I2 Rt= (5)2 × (20) × 30 = 25 × 20 × 30 = 15000 J.

8 XS C I E N C E

4. If resistances are R, then in series = 2R

In parallel = R2

H in series = I2 2RtH in parallel = I2 Rt/2

Ratio = t

t

2

22I R

I R /2 =

41

= 4 : 1.

5. Under conditions of temperature and pressure remaining constant, electric current passingthrough a circuit is directly proportional to applied voltage.

6. (a) Silver is a better conductor. (b) Silver

WORKSHEET-6

1. Highest by connecting all of them in series = 4 + 8 + 12 + 24 = 48 Ω

Lowest by connecting all of them in parallel =1 1 1 14 8 12 24

+ + + = 6 3 2 1

24+ + +

= 1224

R = 2 Ω.2. When we connect them in parallel, then:

(i) Effective resistance of circuit reduces, therefore, large current flows.(ii) If one appliance is not working, others would continue to work.

3. Ohms law states V ∝ ITherefore, resistance remaining constant, the electric current would also be reduced to halfits original value if voltage is reduced to half.

4. Energy = Power × TimeTV set = ETV = 250 watt × 1 hr = 250 Wh = 0.25 kWh

Toaster = Etoaster = 1200 watt × 1060

hr = 200 Wh = 0.20 kWh

ETV > Etoaster.5. SI unit is joules; commercial unit is kWh.

1 kWh = 1000 watt × 1 hour= 1000 watt × 3600 sec= 3.6 × 106 watt sec = 3.6 × 106 joules


6. These are special kind of material where conductivity increases with decrease of temperature.Here, resistance reduces almost to zero at low temperature, e.g., liquid nitrogen (N2).

7. R = ρ lA

R1 = 20 Ω l1 = l A1 = AR2 = ? l2 = 2l A2 = A/2

1

2

RR

=ll1 2

2 1

AA

= l

l

A2

2 A

1

2

RR

=14

⇒ 2 1R 4 R=

8. (a) Formula used V = IRRCE = 2 + 4 = 6 Ω.

(b) I = VR

; R = 3 Ω; V = 3 V ∴ I = 1 A.

(c) IAB = AB

AB

VR

= 36

= 12

A

ICE = CE

CE

VR

= 36

= 12

A.

(d) P.D2Ω = 12

× 2 = 1 V; P4Ω= 12

× 4 = 2 V.

WORKSHEET-7

1. (a) P = VI = 2.5 × 750 × 103 = 1875 × 103 = 1.875 W.(b) R = V/I = 2.5/750 × 103 = 3.33 Ω.(c) E = P × t = 1.875 × 4 = 7.5 Wh = 7.5 × 103 kWh.

2. Let the same resistances be x and other be y, thenSeries; x + x + y = 30 or 2x + y = 30

Parallel,1 1 1x x y

+ + = 13

or2x

y+ = 3

Solving, we get x = 18 Ωy = 6 Ω.

3. (a)1R

= 1 1 18 8 4

+ + = 1 1 2 4

8 8+ + =

R = 2 Ω.

(b)1R

= 1 1 17 8 4

+ +

1R

= 8 7 14

56+ +

= 2956

or R = 5629

Ω.

10 XS C I E N C E

4. (a) Power = I2R = (4)2 × 60 = 16 × 60 = 960 W.(b) V = IR = 4 × 60 = 240 V.(c) t = 2 × 60 = 120 sec

E = P × t = = I2R t = 960 × 2 × 60 = 115200 joules.5. (a) Total resistance will be 4 times original, i.e., 4 Ω.

(b) It will be 2.5 Ω.

(c) Since R ∝ lA

∴ Resultant (R) = R 6

=4 4

= 1.5 Ω.

6. (a) Key open, then R = 12 Ω, V = 6 V ∴ I = VR

= 0.5 A.

(b) Key closed, then R = 6 Ω, V = 6 V ∴ I = VR

= 1 A.

WORKSHEET-8

1. P.D. between AB is 4 V. ( ä V = IR)P.D. between BC is 8 V.

2. Sometimes, live and neutral wires may accidentally touch each other. As a result, theresistance reduces and a large amount of electric current passes, which may lead to electricfires. Overloading occurs when we connect a large number of appliances in the same circuit.

3. (a) = + =1 1 14 4 2

So Resistance between A and B is 6 Ω.

(b) Resistance between A and B = 2 + 1 + 3 + 1 + 2 + 1 + 3 = 13 Ω.

(c) Resistance between A and B is

= 1 1 28 8 8

+ = ; So, R = 4 Ω.

4. It is a process of providing an alternative path to excessive charge that may sometimes leak of thebody of a high voltage metallic appliance. The colour of earth wire is green. One end of this wireis connected to the appliance and the other is earthed. Earth is always at zero potential, thereforeany extra charge successfully reaches earth without affecting appliances thus, preventing shocks.

5. It is a safety device made up of a high resistance with low melting point, which works onprinciple of heating effect of electric current. No, because a fuse will not work effectively ifused this way. Commonly used is alloys of copper and tin.

6. It is 220 V A.C. with 50 Hz frequency. 50 Hz specify frequency of alternating current. House-holdcircuits have parallel arrangement because if something goes wrong with one appliance othershould not be effective. Also in parallel arrangement, all appliances get same voltage input.


WORKSHEET-9

1. (a) (i) Opposite charges attract and like charges repel.(ii) The basic charge is 1.6 × 1019 C which can be positive or negative.

(b) Whenever there are two charges q1 and q2 separated by a distance r then there exist aforce F of attraction or repulsion, which is directly proportional to product of chargesand inversely to square of distance between them.

i.e., F ∝ 1 22

q q

r2.

3. (a) Under physical conditions of temperature and pressure remaining constant, electric currentflowing through a given circuit is directly proportional to applied potential difference.

(b) Set up a circuit as shown in fig. consisting of a nichrome wire XY of length, say 0.5 m,an ammeter, a voltmeter and four cells of 1.5 V each. (Nichrome is an alloy of nickel,chromium, manganese and iron metals.)

First use only one cell as the source in the circuit. Note the reading in the ammeter I,for the current and reading of the voltmeter V for the potential difference across thenichrome wire XY in the circuit. Tabulate them in the table given.

Next connect two cells in the circuit and note the respective readings on the ammeterand voltmeter for the values of current through the nichrome wire and potential differenceacross the nichrome wire.

Repeat the above steps using three cells and then four cells in the circuit separately. Calculate the ratio of V to I for each pair of potential difference V and current I.

S. Number of cells Current through the Potential difference V/INo. used in the nichrome wire, I across the nichrome (volt/ampere)

circuit (ampere) wire, V (volt)

1 12 23 34 4

Plot a graph between V and I, and observe the nature of the graph.

12 XS C I E N C E

In this activity, you will find that approximately the same value for V/I is obtained in eachcase. Thus, the V-I graph is a straight line that passes through the origin of the graph, asshown in fig. Thus, V/I is a constant ratio.

(c) V-I graph for a nichrome wire

4. When charges are separated due to friction between two surfaces, it is called frictionalelectricity. Since here charges are separated but they do not move, it is also known asstatic electricity.(a) On rubbing glass rod with silk, glass rod acquires positive charge and silk acquires

negative charge.(b) Ebonite when rubbed with fur gets negative charge whereas fur gets positive charge.

WORKSHEET-10

1. (a) (i) It means 1 joule of work is required to be done in order to move 1 coulomb of chargesbetween these two points. Voltmeter is the device which is used to measure potentialdifference across a conductor.

(ii) Q = 5 C; V = 12 VEnergy given to charge; W = VQ = 12 × 5 = 60 J.

(b) ! Complete an electric circuit consisting of a cell, an ammeter, a nichrome wire oflength l [say, marked (1)] and a plug key, as shown in Fig.


! Now, plug the key. Note the current in the ammeter.! Replace the nichrome wire by another nichrome wire of same thickness but twice the

length, that is 2l [marked (2) in the Fig.].! Note the ammeter reading.! Now replace the wire by a thicker nichrome wire, of the same length l [marked (3)].

A thicker wire has a larger cross-sectional area. Again note down the current throughthe circuit.

! Instead of taking a nichrome wire, connect a copper wire [marked (4) in Fig.] in thecircuit. Let the wire be of the same length and same area of cross-section as that ofthe first nichrome wire [marked (1)]. Note the value of the current.

! Notice the difference in the current in all cases.

WORKSHEET-11

1. (b) 2. (c) 3. (b) 4. (b) 5. (b) 6. (c) 7. (b) 8. (c) 9. (c)

WORKSHEET-12

1. (c) 2. (d) 3. (c) 4. (d) 5. (c) 6. (c) 7. (b) 8. (b)

WORKSHEET-13

1. (b) 2. (b) 3. (d) 4. (c) 5. (a) 6. (c) 7. (a) 8. (c) 9. (d)

WORKSHEET-141. (b) 2. (c) 3. (c) 4. (d) 5. (d) 6. (d) 7. (c) 8. (c) 9. (c) 10. (c)

WORKSHEET-151. (d) 2. (a) 3. (a) 4. (c) 5. (c) 6. (b) 7. (d)

WORKSHEET-161. (c) 2. (d) 3. (c) 4. (a) 5. (b) 6. (b) 7. (b)

WORKSHEET-171. (d) 2. (c) 3. (a) 4. (d) 5. (c) 6. (c)

WORKSHEET-181. (d) 2. (b) 3. (d) 4. (b) 5. (a)

1. (a) 2. (b)

3. E = P × t = 4 × 5 = 20 Wsec. = 20 J.4. Electrical resistivity is the resistance offered by conductor of unit length and unit area of

cross-section. Current decreases because according to Ohms law RI1

∝ also R ∝ l.

5. Physical conditions of temperature remaining constant, the electric current flowing througha given circuit is directly proportional to applied p.d.i.e., I ∝ V; V = I R.

14 XS C I E N C E

6. (a) Because (i) Effective resistance of circuit is less (ii) If one appliance doesnt work, other canwork.

(b) Because fuse is used to cut off the excessive current flowing through the circuit usingheating effect.

7. (a) No, because in series, effective resistance increases so, current decreases also the appliedp.d. is different.

(b) In series circuit, no bulb will glow whereas in parallel circuit, the rest of the bulbs willglow.

8. According to Joules law of heating; heat energy produced in a circuit is H ∝ I2 (Current)

∝ Resistance∝ Time

H ∝ I2 Rt or H = I2 R t.(a) Applications in electric geyser, heater, ovens and electric bulb.(b) Alloys are preferred than pure metals because (i) They have high resistivity in comparison

to constituent metals. (ii) They dont oxidise on heating.9. If two 8 Ω resistors are connected in series,

(a) ∴ Effective resistance (R) = R1 + R2

= 8 + 8 = 16 Ω.

(b) I =VR =

44 = 1 A.

(c) V = 4 V.

(d) P = I V

= 1 × 4 = 4 W.

(e) Current flowing through 16 Ω combination

i.e., I =VR =

416 = 0.25 A.

∴ Difference in ammeter readings

= 1 0.25 = 0.75 A.

15M A G N E T I C E F F E C T S O F E L E C T R I C C U R R E N T

WORKSHEET-23

1. (a) 2. (b) 3. (c) 4. (a) 5. (a) 6. (c) 7. (c) 8. (b) 9. (c) 10. (d)11. (d) 12. (d) 13. (b) 14. (a) 15. (b) 16. (b)

WORKSHEET-241. It is a naturally occurring or a man-made material which attracts materials of same type or

certain other materials.2. Naturally occurring magnetLodestone (Magnetite)

Man-made magnetAlnico3. (1) Directional propertyWhen suspended freely always point towards earth magnetic north

and south poles.(2) Attractive propertyAttracts magnetic materials and other magnets.

4. Materials which are attracted by a magnet are known as magnetic materials, e.g., steel, iron.5. Electromagnet has the ability to behave like a magnet only when electric current passes

through it unlike permanent magnet. The polarity of its poles and strength of magnet can bechanged in case of electromagnet.

6. Alnico, Nipermag.7. Flemings right hand thumb rule. If we stretch thumb of right hand in the direction of

electric current, then folded fingers give the direction of induced magnetic field.8. These are imaginary lines drawn to indicate the path taken by a compass when moved

around a magnet.9. (a) These originate at north pole and end at south pole to form a closed loop.

(b) No two field lines can intersect each other.10. (a) tesla (b) weber (c) oersted11. 104, 104

12. (a) It is used in cranes for lifting heavy loads.(b) It is used in electric bells.

13. (1) Loudspeakers, speaker of telephones. (2) Galvanometer, Voltmeter, etc.14. (a) Electric GeneratorMechanical energy (coil) → Electrical energy.

(b) Electric MotorElectric energy → Mechanical energy (coil)15. Cu and tin alloy.16. It is the region around a magnet within which another magnet/magnetic material can

experience force of attraction or repulsion due to it.17. Imaginary lines drawn to indicate the path taken by a compass around a magnet.18. By inserting the steel bar inside the solenoid and switching on electric current.19. By using a compass, which shows deflection.20. When they are perpendicular to each other.

2 MAGNETIC EFFECTS OF ELECTRICCURRENT

16 XS C I E N C E

WORKSHEET-251. Magnetic field intensity will directly proportional to current and inversely to radius. So

doubles with current and twice when radius is halved.2. Magnetic field strength, scalar.3. Flemings left hand rule.4. Force experienced depends on magnitude of current and perpendicular distance between

conductor and point.5. Induced magnetic field will be in the form of concentric circles in the plane of the paper.6. Yes.7. Magnitude of electric current, perpendicular distance between that point and conductor.8. It is a coil of many turns wound in the form of a cylinder.9. Electric motor has split rings whereas electric generator has slip ring commutator.

10. A transformer works on the principle the varying magnetic field induces emf and varyingelectric field induces magnetic behaviour.

11. Whenever magnetic field associated with a conductor changes, an emf is induced in it.12. D.C. has constant magnitude and same direction. A.C. vary in magnitude and direction.13. (a) The galvanometer shows a deflection.

(b) The galvanometer shows deflection in other direction.(c) No deflection in galvanometer.

14. Electromagnets are temporary and strong magnets. They possess the properties of a magnetonly when an electric current flows through the coil.

15. ! Fix a sheet of white paper on a drawing board using some adhesive material.! Place a bar magnet in the centre of it.! Sprinkle some iron filings uniformly around the bar magnet. A salt-sprinkler may be

used for this purpose.

! Now, tap the board gently.

WORKSHEET-26

1.

17M A G N E T I C E F F E C T S O F E L E C T R I C C U R R E N T

2.

3.

4. F = BIL, where B = Magnetic field, I = Current, L = Distance.Force is maximum when magnetic field is perpendicular to the plane of coil.

5.

6. (a) It varies inversely with radius.

(b) It varies directly with number of turns of wire in the coil.

(c) It varies directly with the strength of current flowing in the coil.

7. (a) The strength of magnetic field increases. (b) The strength of magnetic field increases.

(c) The polarity or direction of field lines reverses.

WORKSHEET-271. (a) Magnetic field. It is the region around a magnet within which another magnet or a

magnetic substance experiences force of attraction due to it.Direction of magnetic field lines can be determined by:(i) using a compass, where needle points

(ii) by drawing tangent to field lines at that point.

18 XS C I E N C E

(b) Right hand thumb rule. If we stretch thumb of right hand and fold the fingers then thumbindicates the direction of current and folded fingers the direction of induced magnetic field.

1. (c) 2. (d) 3. AC. Current which varies in its magnitude and changes direction continuously.

DC. Current which has a constant magnitude and no change in direction.4. (i) A thin beam of alpha particles will have a magnetic field around it being a charged particle.

(ii) A beam of neutrons will not have any field as these are uncharged.5. It depends on direction of magnetic field, direction of electric current and direction of

motion of conductor.6. Conversion of electrical energy to mechanical energy, power of commercial motor can be

enhanced by using:(i) Electromagnet in place of permanent magnet.

(ii) Large numbers of turns of conducting wire in current carrying coil.(iii) Soft iron core.

7. Current drawn by oven = 2000

= 220

9.09 A.

Rating of fuse 5A. This will not let the oven draw is required value of current. It must bereplaced by 10A fuse.

8. (a) Over loading. It occurs when we connect a number of appliance in the same socket.(b) Short circuiting. It occurs when live and neutral wires accidentally touch each other

resulting in electrical sparks.(c) Earthing. The phenomenon of providing an alternating path to excessive charge that

may sometimes leak to andy to high voltage appliance by connecting it to earth.9. Principle. Conversion of mechanical energy to electrical energy.

An A.C. generator can be converted to D.C. generator by changing slip rings with split ringcommutators.

19S O U R C E S O F E N E R G Y

WORKSHEET-31

1. (c) Fossil fuels 2. (d) Infrared rays

3. (b) Cloudy day 4. (c) Both silicon and silver

5. (c) Nuclear energy 6. (c) 0.7 watt

7. (d) All of these 8. (d) All of these

9. (d) All of these 10. (c) Ground water

11. (b) 15 km/hr 12. (d) All of these

13. (b) Nuclear energy 14. (d) All of these

15. (a) Coal 16. (d) All of these

WORKSHEET-32

1. The usual components of biogas are methane, carbon dioxide, hydrogen and hydrogensulphide.

2. Cow dung cake.

3. Hot spots are those regions on earths crust under which molten rocks have been trappeddue to push from deeper hot areas.

The energy obtained from hot molten rocks beneath the earths surface is called geothermalenergy.

4. Wind energy farm is the large area over which number of wind mills have been erected.Output of one wind mill is not enough to generate electricity at commercial level.

5. Charcoal

6. Charcoal is better than wood as fuel because it burns without flame, is comparativelysmokeless and has a higher heat generation efficiency.

7. Biogas and manure.

8. A solar cell is a device to convert solar energy to electricity.

9. A solar cell panel is an arrangement of large number of solar cells in combination that candeliver enough electricity for practical use.

10. Solar cooker and solar heater.

11. Problems associated with construction of dams are submergence of agricultural and residentialland, destruction of large ecosystems, production of polluting gas methane from submergedvegetation, etc.

12. It checks the exit of infrared rays.

13. Silicon and silver.

14. Geothermal energy.

15. Oxides of nitrogen and sulphur.

3 SOURCES OF ENERGY

20 XS C I E N C E

16. Water gets recycled through hydrological cycle hence, it gets refilled in reservoir of damseach time it rains thus, its potential energy can be generated again and again.

17. Nuclear fusion.

18. Compressed Natural Gas.

19. CNG is environment-friendly as it does not produce pollution of any type.

20. 0.7 watt.

21. Black surface is preferred for making solar devices because it absorbs more heat as comparedto white or reflecting surface under identical conditions.

22. Methane and sulphur dioxide.

WORKSHEET-33

1. A good source of energy is the one which is easily available, economical, pollution free andconvenient to use.

2. Yes, wind, water, ocean are some of the examples of pollution free source of energy. Theydo not leave any residue or poisonous gases.

3. We are looking at alternate sources of energy to replace the conventional sources which arenon-renewable and causing pollution of the environment.

4. Now they are used to run turbines and produce electricity.

5. The increase in the demand for energy is affecting our environment adversely as:

! It puts a pressure on source of energy as well as increases the investment on the powerstations.

! Since most of the energy is produced from coal, petroleum, hence, acid rain, global warmingand other pollution related problems are caused.

6. (a) CNG is non-renewable while hydrogen is renewable fuel.

(b) Hydrogen on burning produces only water vapours while CNG on burning producesgreenhouse gases which may lead to global warming hence, hydrogen is a cleaner fuelthan CNG.

OR

Yes, it does not produce poisonous gases at all.

7. I would use renewable and pollution free sources of energy to heat my food. Because, it wouldnot disturb the ecological balance as well as it would be reproduced in nature by cyclic processwhen it would be used once.

OR

Four characteristics of biogas are:

! High heating capacity! Burns without smoke! Leaves no residue! Can be easily used for cooking, heating and lighting.

8. (a) Winds. It can be established only in those areas where wind blows at a higher speed than15 km/hour to maintain the required speed of the turbine.

(b) Tides. The locations where dams to harness this energy can be built, are limited.


9. We classify energy sources as:

(a) Renewable when its source is replenished in nature through fast natural cycle such asflowing water of river, biomass.

Non-renewable when its source is being replenished through very slow natural cycles,e.g., coal and petroleum.

(b) Exhaustible when its source may get over in nature due to over-use and mismanagementby us, e.g., coal, wood.

Inexhaustible when its source can never be over whatever amount we may use, e.g.,wind energy, ocean energy.

WORKSHEET-34

1. X-rays.

2. Burning wood in traditional chulhas is considered disadvantageous as it does not yieldmuch energy but lot of smoke to pollute the environment.

3. Turbine.

4. Solar energy of solar cell panels.

5. Fossil fuels are the non-renewable fuel formed due to burying of plants and animals underlayers of earth, millions of years ago. Coal and petroleum.

6. Coal and oil are the fuels used to produce heat energy to convert water to steam which inturn rotates (mechanical energy) the turbines in power plant. Transmission of electricity ismore efficient than transporting coal and petroleum over the same distance. Being nearthem, expense of transport can be reduced.

7. The purpose behind the use of reflector in solar devices is to focus the sunrays to achievehigher temperatures.

8. Biogas is considered as a clean fuel because it does not produce smoke or any harmful gases.

9. Digester in a biogas plant is a sealed chamber in which there is no oxygen. In this chamberanaerobic organisms break down complex compounds in cow dung slurry to gases likemethane, carbon dioxide, hydrogen and hydrogen sulphide (Biogas).

10. The basis of nuclear energy is nuclear fission process. The nucleus of a heavy atom such asuranium, plutonium or thorium when bombarded with low energy neutrons, can be splitapart into lighter nuclei. When this is done, a tremendous amount of energy is released.Fission of one atom of uranium releases 10 million times the energy produced by thecombustion of an atom from coal.

11. Two advantages of classifying energy sources as renewable and non-renewable are:

(a) The non-renewable sources can be substituted by renewable once thus, decreasing thepollution caused by them.

(b) Enough resource and a pollution free environment can be left for the future generationensuring sustainable development.

12. A good fuel is the one which is easily available at economical prices and gives enoughenergy without producing much pollution.

13. Fossil fuels are non-renewable and produce large amount of smoke, acidic and greenhousegases.

22 XS C I E N C E

14. We can reduce the pollution caused by fossil fuels increasing the efficiency of combustionprocesses and using various techniques to reduce the escape of harmful gases and ashes intothe surroundings.

WORKSHEET-35

1. Biomass is source of fuel obtained from plant or animal products, for example cow dungcakes, wood, biogas, etc.

2. Petroleum and natural gas.

On refining petroleum, the products obtained from it can be used as fuels. Natural gas isanother important fossil fuel that is found with petroleum in oil wells. There are, however,some oil wells, which yield only natural gas. Natural gas mainly contains methane and canbe burnt easily to produce heat.

3. Fractional distillation.

Products obtained are paraffin wax, fuel oil, petrol, kerosene, diesel and natural gas.

4. Turbine is a device made up of a rotor blade assembly. Moving turbine rotates the armatureof the electric generators to produce electricity.

5. (a) Windmills are designed to convert wind energy into mechanical or electrical energy. Awindmill essentially consists of a structure similar to a large electric fan that is erected atsome height on a rigid support.

(b) Energy of flowing water is utilised to produce electricity on a large scale at hydroelectricpower plants.

(c) The heat from inside of the earth can be utilized as a source of energy under certainfavourable conditions that are created by natural processes. This is known as geothermalenergy.

6. Some ways which we can follow to address the problems of energy crisis:

(a) Increasing efficiency of machines and gadgets so that they consume less energy but givemore output such as fluorescent tubes.

(b) Using alternate forms of energy which is based on renewable sources like wind, oceans,nuclear or flowing water.

(c) Economizing use of gadgets by using carpools, walking more, wearing extra woollen inwinters.

(d) Reducing stress on industries as they have less demand on them and save energydemand by them.

(e) Using less electricity by switching off lights and fans when not in use.

7. There are many controversies associated with the construction of hydroelectric power plantslike Narmada dam. For example, when dams are built on rivers, large land areas getsubmerged. This may cause many problems like submergence of agricultural and residentialland, destruction of large ecosystems, production of polluting gas methane from submergedvegetation, etc.


WORKSHEET-36

1. Firewood should be replaced by alternative sources of energy as:

(a) It does not yield much energy.

(b) It produces lot of smoke to pollute the environment.

(c) It can lead to deforestation and related problems.

(d) Other fuels like charcoal is better than wood as fuel because it burns without flame, iscomparatively smokeless and has a higher heat generation efficiency.

2. Some of the criteria for selecting a good fuel

(a) easy availability;

(b) low cost;

(c) no problem in storing and transport;

(d ) a high calorific value;

(e) low content of non-combustibles (In other words, the residue left after combustionshould be as low as possible.) and

( f ) no combustion products that are poisonous or environmental pollutants.

3. (a) Raw materials required in biogas plant

Residues after crop harvest, vegetable waste, cow dung, sewage.

(b) Role of anaerobes

Anaerobic organisms break down complex compounds in cow dung slurry to biogas indigester in a biogas plant.

(c) Composition of biogas

Gases like methane, carbon dioxide, hydrogen and hydrogen sulphide.

(d) Advantages over other fuels

As a fuel it has high heating capacity. Does not produce ashes or polluting gases.

(e) Uses

Fuel for heating, lighting and running machines. Slurry can be used as manure as it isrich in nitrogen and phosphorus. Safe and efficient method to dispose of waste.

4.

24 XS C I E N C E

WORKSHEET-371. The advantages of using solar energy

(a) Solar cells provide a clean, pollution-free and environment-friendly source of electricity.

(b) These can be used anywhere as a self-generating source of electricity.

Disadvantages of using solar energy

(a) High cost for their installation. Availability of special grade silicon required for makingsolar cells is only limited.

(b) The technology to obtain silicon in pure form, too, is quite expensive.

2. Conventional sources like coal, petroleum, wood (biomass).Alternate sources like solar, nuclear, geothermal, etc.Air pollution is caused due to excessive use of fossil fuels. The amount of greenhouse gaseslike methane, carbon dioxide and carbon monoxide increase in air. They trap the heat energyof sun during the day, not letting it escape even at night. It leads to gradual increase intemperature of earth; it is known as global warming. Due to this, ice will melt at pole andincrease the level of water in oceans and seas.

Alternate sources do not cause so much of pollution but they need maintenance andinfrastructure. Some of the sources are unpredictable like wind energy, ocean energy.Based on their merits, solar energy is one of the best.

1. (b) 2. (d)

3. (a) It should be able to do large amount of work per unit volume. (b) It should be easily accessible.

4. (a) Ocean thermal energy (b) Tidal enrgy.

5. The role of plane mirror is to reflect mass of sunlight towards the centre of box.

The role of glass sheet is to trap suns rays inside the box so as to increase the temperature.

6. Fuels obtained from plants and animal products are called biomass. Biomass can be used inbiogas plant to obtain biogas and remaining slurry can be used as a good manure.

7. Nuclear fission. It is splitting of a heavy unstable nuclear into its smaller nuclei with releaseof large amount of energy.

Disadvantages. (a) Release of harmful radioactive radian. (b) Release of radioactive wastes.

8. Use of fossil fuels may lead to an pollution exhaustion of fossil fuel. Steps to minimise thepollution are: (a) change to clean fuel like CNG. (b) promote use of solar cells hence, solar energy.

9. Biomass is fuel obtained form animal and plant products. Its principle is conversion ofbiomass in absence of oxygen to obtain biogas and slurry.


CHEMISTRY

26 XS C I E N C E

WORKSHEET-401. (d) Cooking of food

2. (c) Magnesium ribbon burns with a dazzling white flame and changes into a white powder.

3. (d) Al2(SO4)3

4. (c) aq

5. (d) The gas evolved is chlorine.

6. (b) Chemical reaction

7. (a) Hydrogen gas and iron chloride are produced.

8. (b) Reactants

9. (b) ↓10. (d) Zn (s) + H2SO4 (aq) → ZnSO4 (aq) + H2 (g)

11. (d) Mass of the reactants is greater than mass of the products

12. (c) 2 volumes of hydrogen gas is evolved at cathode

13. (a) The colour of the crystals changes from light green to yellow

14. (d) All of these

15. (b) The colour of solution changes to green

16. (d) Double displacement reaction

17. (a) CaO mixed with water

18. (d) Displacement reaction

19. (d) (iii) and (iv)

20. (c) A yellow precipitate of lead iodide is formed

21. (a) Oxidation of copper

22. (b) X = Ag, Y = Ag2S

WORKSHEET-411. (d) All of these

2. (b) 2AgBr (s) → 2Ag (s) + Br2 (g)

3. (a) Oxidation

4. (a) H2S is getting oxidised

5. An unbalanced chemical equation is called skeletal equation. Here the mass of the reactants

is not equal to the mass of products, e.g., Mg + O2 ∆→ MgO

6. An equation that has equal number of atoms of each element on both the sides of equationis called balanced chemical equation, i.e., mass of the reactants is equal to mass of the

products. e.g., 2Mg + O2 ∆→ 2MgO

4 CHEMICAL REACTIONS AND EQUATIONS

27C H E M I C A L R E A C T I O N S A N D E Q U A T I O N S

7. An equation is balanced in order to satisfy law of conservation of mass according to whichtotal mass of the reactants is equal to the total mass of the products, i.e., mass can neither becreated nor be destroyed during any chemical change.

8. (a) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O(b) 2NaOH + H2SO4 → Na2SO4 + 2H2O(c) NaCl + AgNO3 → AgCl + NaNO3

9. (a) BaCl2 + H2SO4 → BaSO4 + 2HCl

(b) CH4 + 2O2 → CO2 + 2H2O

(c) 2FeSO4∆→ Fe2O3 + SO2 + SO3

(d) 2Pb(NO3)2∆→ 2PbO + 4NO2 + O2

(e) 2KClO3∆→ 2KCl + 3O2

10. (a) Ca(OH)2 + CO2 → CaCO3 + H2O

(b) Zn + 2AgNO3 → Zn(NO3)2 + 2Ag

(c) 2Al + 3CuCl2 → 2AlCl3 + 3Cu

(d) BaCl2 + K2SO4 → 2KCl + BaSO4

11. (a) 3H2 + N2 → 2NH3 (Combination reaction)

(b) 2H2S + 3O2 → 2H2O + 2SO2 (Redox reaction)

(c) 3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4↓ (Double displacement)

(d) 2K + 2H2O → 2KOH + H2 (Displacement reaction)

(e) CH4 + 2O2∆→ CO2 + 2H2O (Oxidation reaction)

(f) CaO + H2O → Ca(OH)2 (Combination reaction)

(g) 2Al2O3Electriccurrent

→ 4Al + 3O2 (Decomposition reaction)

WORKSHEET-421. The Chemical equation can be made more informative by:

(a) Mentioning the physical states of the reactants and products along with their chemicalformula in brackets.

(b) The reaction conditions, e.g., temperature, pressure, catalyst etc., are indicated above orbelow the arrow.

(c) The gas released is indicated by arrow upwards ↑ while the precipitate formed by arrowdownwards ↓.

(d) For an exothermic reaction, + Heat is written along with products, while for anendothermic reaction, + Heat is written along with reactants.

28 XS C I E N C E

2. Magnesium being a reactive metal combines with oxygen of air to form a layer of magnesiumoxide on its surface. Hence, it should be cleaned with a sand paper before burning toremove the oxide layer formed on its surface.

3. (a) At anode, oxygen gas is evolved while hydrogen gas is evolved at cathode.

(b) The gases, hydrogen and oxygen evolved at cathode and anode are in the ratio of 2:1according to the equation:

Electric2 2 2current

2H O 2H O→ +

4. (a) C + O2 → CO2

(b) CaO (s) + H2O (l) → Ca(OH)2 (aq)

5. The food we eat contains carbohydrates. On digestion, these carbohydrates breakdown intoglucose. During respiration this glucose combines with oxygen in the cells of our body andconverts it into carbon dioxide and water with release of heat energy. Hence, respiration isan exothermic process.

6. When dilute sulphuric acid is poured on zinc granules, bubbles of hydrogen gas are evolvedfrom the surface of zinc metal and the reaction mixture becomes hot.

Zn + H2SO4 (aq) → ZnSO4 + H2↑7. In a single displacement reaction, a more reactive metal displaces a less reactive metal from

its salt solution, e.g.

Fe + CuSO4(aq) → FeSO4(aq) + Cu

Iron being more reactive than copper displaces copper from its salt solution, while in adouble displacement reaction the exchange of ions takes place between the reactants. e.g., onmixing aqueous solutions of barium chloride and sodium sulphate, barium ions and sodiumions exchange their position.

BaCl2(aq) + Na2SO4(aq) → BaSO4↓ + 2NaCl

8. The process of decomposition carried out under the effect of heat is called thermaldecomposition. Here, a single reactant breaks down to form simpler products, e.g.

CaCO3 heat→ CaO + CO2

WORKSHEET-43

1. The reactions which involve the formation of an insoluble substance is called precipitationreactions. A precipitate is generally obtained when aqueous solutions of two substances aremixed together, e.g., mixing of aqueous solutions of sodium chloride and silver nitrate formsan insoluble precipitate of silver chloride.

NaCl(aq) + AgNO3(aq) → AgCl↓ + NaNO3(aq)

2. (a) Observation:

1. The colour of crystals changes from green to reddish brown due to formation ofiron (III) oxide.

2. Pungent smelling gases sulphur dioxide and sulphur trioxide are evolved.

(b) Observation:

1. The colour of crystals changes from white to yellow.

2. Reddish brown fumes of nitrogen dioxide are evolved.


3. (a) On mixing an aqueous solution of sodium sulphate and barium chloride, doubledisplacement reaction takes place with the formation of white precipitate of bariumsulphate.

(b) Double displacement reaction/Precipitation reaction.

4. (a) Insoluble product is lead iodide, which is yellow-coloured.

(b) Pb(NO3)2 + 2KI → PbI2 + 2KNO3.

5. Iron which is coated with molten zinc by dipping iron in molten zinc is called galvanisediron.

Zinc is more reactive than iron. On coating zinc over iron which has a better tendency to getoxidised as compared to iron easily gets oxidised on exposure to moist air and saving ironfrom being rusted.

6. (a) Iron objects acquire reddish brown coating on exposure to moist air, due to formation ofhydrated oxide of iron formed by rusting of iron. Chemical process responsible for theformation of reddish coating is rusting and the red coat formed is hydrated oxide ofiron/rust.

(b) Iron articles are highly prone to the process of rusting in the presence of moist air. Toprevent them from getting rusted, they are generally painted.

7. Decomposition reactions are called opposite of combination reactions because in adecomposition reaction, a single compound breaks down to form two or more simplersubstances under the effect of heat, light or electric current, whereas in a combinationreaction two or more substances combine to form a single product, e.g.

CaCO3 ∆→ CaO + CO2 (decomposition)

2Mg + O2 ∆→ 2MgO (combination)

8. (a) Decomposition reaction.

(b) 2FeSO4(s) heat→ Fe2O3(s) + SO2(g) + SO3(g)

Ferrous sulphate Ferric oxide Sulphur Sulphur

dioxide trioxide

9. (a) Oxidation is a process of addition of oxygen to a substance or removal of hydrogen froma substance, e.g.

2Cu + O2 ∆→ 2CuO.

Copper is getting oxidised to CuO, as oxygen is added to copper.

(b) It is the process of removal of oxygen from a substance or addition of hydrogen to asubstance, e.g.

CuO + H2 ∆→ Cu + H2O

Copper oxide is reduced to copper as it involves removal of oxygen.

30 XS C I E N C E

WORKSHEET-44

1. (a) Substance getting oxidised H2 to H2O

Substance getting reduced CuO to Cu

(b) Substance getting oxidised HCl to Cl2Substance getting reduced MnO2 to MnCl2

(c) Substance getting oxidised H2S to S

Substance getting reduced SO2 to S

(d) Substance getting oxidised Na to Na+

Substance getting reduced O2 to O2

2. Exothermic reactions. Those reactions which proceed with the evolution of heat energy arecalled exothermic reactions, e.g., burning of fuels, respiration.

Endothermic reactions. Those reactions which proceed with the absorption of heat energyare called endothermic reactions, e.g., decomposition of calcium carbonate using heat energy.

3. Decomposition of calcium carbonate gives calcium oxide and carbon dioxide. Calcium oxideobtained is used in the manufacture of cement.

4. The oxidation of oil and fats present in food materials to form products that have bad odourand taste is called rancidity.

5. Oil and fat containing food items are generally flushed with nitrogen to prevent the oxidationof oil and fats. Nitrogen being an inert gas does not react with oils and fats, prevents theoxidation of oils and fats and thus, they last longer without turning rancid.

6. The two different methods used to prevent the food from getting rancid are:

(1) Keep food in air tight containers.

(2) Addition of anti-oxidants to foods containing fats and oil.

7. Reaction (i) and (iii) are possible

(i) Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)Zinc Copper sulphate Zinc sulphate Copper

(Blue) (Colourless)

Zinc is more reactive than copper, therefore, it can displace copper from copper sulphatesolution.

(iii) Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s)

Zn is more reactive than Fe, therefore, it can displace iron from ferrous sulphate solution.

Reaction (ii) is not possible as iron is less reactive than zinc, hence, it cannot displace Zn.

8. Decomposition of calcium carbonate using heat energy.

CaCO3 ∆→ CaO + CO2

Electrolysis of water using electric current.

2H2O Electriccurrent

→ 2H2 + O2

Decomposition of silver chloride using light.

2AgCl Sunlight→ 2Ag + Cl2


9. Those reactions in which oxidation and reduction take place simultaneously are calledredox reactions, e.g.

Oxidation (loss of hydrogen)

MnO2 + 4HCl (conc.) → MnCl2(aq) + Cl2(g) + 2H2O

Reduction (loss of oxygen)

MnO2 is getting reduced to MnCl2.

HCl is getting oxidised to Cl2.

WORKSHEET-45

1. The two important methods to prevent iron objects from rusting are:

(1) Application of paint, oil/grease on the iron objects.

(2) Galvanization of iron objects. In this process iron is coated with a layer of zinc bydipping the iron object in molten zinc.

2. (a) The gases evolved at anode and cathode are oxygen and hydrogen.

(b) On electrolysis, water decomposes to form hydrogen and oxygen gas in the ratio of 2 : 1by volume according to the equation given below:

2H2O(l) electriccurrent

→ 2H2(g) + O2(g)

The gas collected in double volume is hydrogen.

(c) Test for oxygen. If we bring a burning splinter near the mouth of test tube containingoxygen gas it burns more brightly.

Test for hydrogen. On bringing a burning splinter near the mouth of the test tubecontaining hydrogen, the gas burns with a pop sound.


(b) 2Pb(NO3)2(s) → 2PbO(s) + 4NO2(g) + O2(g)

(c) Reddish brown fumes of nitrogen dioxide along with oxygen gas is evolved.

(d) The colour of the substance changes from white to yellow due to formation of lead oxide.

(e) Lead oxide which is yellow coloured.

WORKSHEET-46

1. (a) Decomposition reaction of a single reactant. Iron sulphate decomposes under the effectof heat to form more than one product.

(b) 2FeSO4(s) → Fe2O3(s) + SO2(g) + SO3(g)

(c) The colour of ferrous sulphate changes from green to reddish brown as it undergoesdecomposition on heating and changes into ferric oxide which is reddish brown in colour.

(d) The pungent smelling gases formed are sulphur dioxide and sulphur trioxide. Odour ofburning sulphur is experienced.

32 XS C I E N C E

2.

Materials Required. Two test tubes, test tube stands, copper sulphate solution, iron sulphatesolution.

Procedure. Take two test tubes. In one of the test tubes, take about 15 ml of copper sulphatesolution and in the another test tube take about 15 ml of iron sulphate solution. Immerse aclean copper coin in iron sulphate solution and an iron nail in copper sulphate solution andwait for few minutes.

Observation. After few minutes we will observe that the colour of copper sulphate solutionchanges from blue to green, while no change takes place in iron sulphate solution.

Conclusion. Iron is more reactive than copper as it displaces copper from its salt solution.

Chemical equation: Fe + CuSO4 → FeSO4 + Cu

Cu + FeSO4 → No reaction.

WORKSHEET-47

1. (b) 2. (c) 3. (d) 4. (d) 5. (a) 6. (a) 7. (a) 8. (c) 9. (c)

10. (d) 11. (c) 12. (b)

1. (d) 2. (c)

3. Silver chloride turns grey in sunlight because silver chloride decomposes in the presence ofsunlight to form grey-silver.

4. (a) When quicklime is mixed with water,

(i) A vigorous reaction takes place.

(ii) Lot of heat energy is released and water starts boiling even without heating.

(b) CaO + H2O Ca(OH)2

5. This is because iron is a more reactive metal than copper. Iron thus displaces copper from itssalt solution due to which iron metal gets used up leading to holes in the vessel.


6. (a) The oxidation of oil and fats present in food materials to form products that have badodour and taste is called rancidity.

(b) Three different methods used to prevent the food from getting rancid are:

1. Keep food in air-tight containers.

2. Addition of anti-oxidants to foods containing fats and oil.

3. Flushing of food items with nitrogen or refrigeration of food items.

7. (a) When lead nitrate crystals are heated strongly, it decomposes to form lead oxide, andgases oxygen and nitrogen dioxide are evolved.

Observation. (a) Reddish-brown fumes of NO2 gas are evolved. (b) Yellow residue of leadoxide is left behind. (c) Crackling sound is heard.

(b) 2Pb(NO3)2 ∆→ 2PbO(s) + 4NO2 (g) + 2O2 (g)

8. (a) X is magnesium and Y is magnesium oxide.

(b) MgO + H2O → Mg(OH)2

(c) Mg is cleaned with a sand paper before burning to evolve the oxide layer formed on itssurface due to its contact with air. This oxide layer slows down the process of combustion.

9. (a) A is zinc, B is iron and C is copper sulphate solution.

(b) Zn (s) + CuSO4 (aq) → ZnSO4 (aq) + Cu (s)

Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)

(c) Single displacement reaction.

(d) Redox Reaction.

34 XS C I E N C E

WORKSHEET-52

1. (b) 2. (d ) 3. (b) 4. (d) 5. (c) 6. (b) 7. (c) 8. (d) 9. (c) 10. (a)

11. (c) 12. (c) 13. (d) 14. (a) 15. (c) 16. (b) 17. (d) 18. (b) 19. (c) 20. (b)

21. (b) 22. (c) 23. (c) 24. (c) 25. (c) 26. (c)

WORKSHEET-53

1. (a) 2. (b) 3. (b) 4. (b) 5. (b) 6. (c) 7. (c) 8. (b) 9. (c) 10. (c)

11. (c) 12. (c) 13. (b) 14. (c) 15. (c) 16. (b) 17. (d) 18. (c) 19. (d) 20. (c)

21. (c) 22. (c) 23. (a) 24. (d)

WORKSHEET-54

1. The acid present in lemon juice is citric acid.

2. Olfactory indicator.

3. An acidic solution turns blue litmus paper red while their is no effect on blue litmus paper bya basic solution.

4. Dry slaked lime [Ca(OH)2].

5. Plaster of Paris. The chemical name of the compound is calcium sulphate hemihydrate.

Formula is CaSO4. 12

H2O.

6. Sodium carbonate.

7. Hydrogen gas.

8. Strong acid: Hydrochloric acid

Weak acid : Acetic acid

9. The salts of sulphuric acid are called sulphates, e.g., calcium sulphate.

10. For the healthy growth of the plant the pH of the soil should be neither too alkaline norhighly acidic.

11. Dilute hydrochloric acid.

12. Methanoic acid.

13. Antacids, e.g., magnesium hydroxide.

14. When pH of rain water is less than 5.6, it is called acid rain.

15. On dilution of an acid solution, the concentration of H+ ions decreases per unit volume.

16. Methyl orange gives yellow colour in basic medium while phenolphthalein gives pink colour.

17. HCl solution shows acidic properties as it contains H+ ions, which is responsible for theacidic nature.

5 ACIDS, BASES AND SALTS

35A C I D S, B A S E S A N D S A L T S

18. Calcium oxychloride commonly known as bleaching power. Formula is : CaOCl2.

19. Water of crystallisation is the fixed number of water molecules chemically attached to eachformula unit of a salt in its crystalline form, e.g., copper sulphate has five water molecules ofcrystallisation.

20. Alkali, e.g., sodium hydroxide (NaOH).

21. On electrolysis of brine, chlorine gas is released at anode and hydrogen gas at cathode.

22. Acidic salt : Ammonium chloride

Basic salt : Sodium acetate

WORKSHEET-55

1. Baking soda.

2. Acidic oxide : Carbon dioxide

Basic oxide : Sodium oxide

3. Those substances which give different colour in different medium and thus indicate thepresence of acid or base in a solution are called acid-base indicators.

4. Natural indicator : Litmus

Synthetic indicator : Phenolphthalein

5. The chemical name of washing soda is sodium carbonate, FormulaNa2CO3.10H2O. It isused for removing permanent hardness of water.

6. The chemical name of bleaching powder is calcium oxychloride. It is prepared by the actionof chlorine on dry slaked lime.

Ca(OH)2 + Cl2 → CaOCl2 + H2O

7. The nature of the solution can be tested by making use of an indicator. We can make use ofblue litmus paper. Dip a blue paper in both the solutions provided to you. The solution thatchanges blue litmus to red is acidic in nature. The other solution which has no effect on theblue litmus paper is distilled water.

8. A solution that contains H+ ions show acidic properties and turns blue litmus paper red.Since dry HCl does not ionise to produce H+ ions, it does not show acidic properties and theiris no effect on the litmus paper.

9. The concentration of hydronium ions (H3O+) decreases per unit volume on diluting an acid,

i.e., the solution becomes less acidic on dilution.

10. On eating spicy food, excess of dilute hydrochloric acid is produced in our stomach. Thisexcess acid produced leads to burning sensation. This can be neutralised by taking antacidswhich are mild bases like magnesium hydroxide.

11. First dip the red litmus paper provided to you in all the three test tubes. The solution thatturns red litmus blue is a basic solution. Then dip the blue litmus paper in the remaining twosolutions. The solution that turns blue litmus red is acidic solution and the solution that hasno effect on red or blue litmus paper is neutral.

12. (a) Neutralisation reaction.

(b) The solution is initially pink in colour as phenolphthalein gives pink colour in basic medium.On adding acid to sodium hydroxide solution, neutralisation reaction takes place with theformation of sodium chloride which is a neutral salt and thus, the colour fades away.

36 XS C I E N C E

WORKSHEET-56

1. When sodium hydrogencarbonate is made to react with dilute hydrochloric acid, carbondioxide gas is evolved.

NaHCO3 + HCI(aq) → NaCl + CO2 + H2O

Test: Pass the gas evolved through limewater. Limewater turns milky indicating the gasevolved is carbon dioxide.

Ca(OH)2 + CO2 → CaCO3 + H2OLimewater Calcium

carbonate

2. (a) Olfactory indicators.

(b) For example, clove oil. It gives different odour in different medium, i.e., acidic and basicmedium.

3. On adding methyl orange to test tubes A and C containing NaOH and Mg(OH)2, yellowcolour is produced while pink colour is produced in test tube B containing acetic acid.

4. (a) Hydrogen gas.

(b) Bring a burning splinter near the mouth of the test tube containing hydrogen gas. It burnswith a pop sound.

(c) It is lighter than air.

(d) The above gas is collected by downward displacement of water, as it is insoluble in water.

5. If few pieces of granulated zinc is warmed with 5 ml of NaOH solution, hydrogen gas isevolved along with the formation of sodium zincate.

Zn(s) + 2NaOH(aq) ∆→ Na2ZnO2 + H2↑(sodium zincate)

6. The black colour of copper oxide changes to bluish green because copper oxide reacts withdilute hydrochloric acid to form copper (II) chloride which is bluish green.

A neutralisation reaction takes place between copper oxide and dilute hydrochloric acid.

CuO + 2HCI → CuCl2 + H2O

7. Curd and sour substances are not stored in brass and copper vessels as they are acidic innature. The acids present in them may react with metals to form toxic compounds which areunfit for human consumption.

8. Although alcohol and glucose contain hydrogen but they do not ionise in solution to produceH+ ions, which are responsible for the acidic properties of a substance. On the other hand,HCl and HNO3 furnish H+ ions in solution and thus, show acidic property.

9. (a) Concentration of solution with pH 6 = 106 M and

pH 8 = 108 M

The solution containing pH of 6 has higher hydrogen ion concentration than the solutionwith pH 8.

(b) Solution of pH 6 is acidic in nature.

10. The solution is basic in nature as it turns red litmus blue. The pH of this solution will be morethan 7.


WORKSHEET-57

1. The concentration of hydrogen ions is directly related to the acidic nature of the solution.Higher is the concentration of H+ ions in the solution, more acidic is the solution.

2. The student will add concentrated sulphuric acid slowly to water taken in a beaker along thesides of the beaker. This is because the addition of acid to water is highly exothermic in natureand if water is added to conc. H2SO4' the heat generated may cause the mixture to splash andcause burns. Even the glass apparatus can break. Thus, add acid to water.

3. (a) Lemon juice 2 (As it is strongly acidic)

(b) Distilled water 7 (As it is neutral)

(c) Sodium hydroxide 14 (As it basic in nature)

(d) Tomato juice 4 (As it is mildly acidic)

4. When we eat chocolates and sweets, some of it sticks to our teeth. Bacteria present in themouth produce acids by degradation of sugar present in the mouth which destroys our toothenamel. This excess acid can be neutralised by using toothpaste which is basic in nature andthus, prevents tooth decay.

5. Pickles are acidic in nature. If they are stored in metal containers, the acids present in pickleswill react with metal containers to form poisonous salts which are unfit for human consumption.

6. Copper sulphate crystals are blue in colour due to presence of five molecules of water ofcrystallisation. On heating strongly copper sulphate crystal loses five molecules of water ofcrystallisation and turns anhydrous, which is white in colour.

CuSO4.5H2O ∆→ CuSO4 + 5H2O

(Blue) (White)

7. When plaster of Paris is mixed with water, it sets into a hard mass due to the formation ofgypsum.

CaSO4. 12

H2O + 112

H2O → CaSO4. 2H2O

(Plaster of Paris) (Gypsum)

8. The stain of curry contains turmeric due to which it is yellow coloured. Turmeric is a naturalindicator. When soap is applied on it, it turns to reddish brown, as soap is basic in nature andturmeric gives brown colour in basic medium. The colour changes back to yellow when wateris applied.

9. (a) Sodium oxide and potassium oxide.

(b) Alkalies.

WORKSHEET-58

1. The process of electrolytic decomposition of aqueous solution of brine to produce sodiumhydroxide, chlorine gas at anode and hydrogen gas at cathode is called chlor-alkali process. Itis so called due to the formation of its products. Sodium hydroxide which is an alkali andchlor represent chlorine gas.

2. The formation of H+ ions is responsible for the acidic properties of the substance. Since acidscannot furnish H+ ions in the absence of water, they cannot show acidic properties.

38 XS C I E N C E

3. When dilute hydrochloric acid is added in a test tube containing few pieces of marble, acolourless gas with brisk effervescence is evolved. The gas evolved is carbon dioxide. Onpassing the evolved gas through limewater, it turns milky due to the formation of insolublecalcium carbonate.

CaCO3 + 2HCl(aq) → CaCl2 + CO2↑ + H2O

(Marble)

Ca(OH)2 + CO2 → CaCO3 + H2O(Limewater) (White precipitate)

4. Plaster of Paris (CaSO4. 12

H2O) has a strong tendency to absorb moisture and gets converted

into gypsum (CaSO4. 2H2O) which sets into a hard mass. Thus, to prevent its contact withmoisture, it is stored in moisture proof container.

5. Distilled water is pure water which does not contain any dissolved salts or gases. Rainwatercontains dissolved gases like CO2 and SO2 which, in turn, produce acids like carbonic acid(H2CO3), sulphurous acid (H2SO3) and dissociate into ions. Formation of ions in rain isresponsible for the conduction of electricity in rain water while due to absence of ions indistilled water, it does not conduct electricity.

6. Lower is the pH of the substance, higher is its acidic strength. Therefore, a substancehaving pH of 2.4 has higher acidic strength while pH of 6.8 has lowest acidic strength.Thus, the increasing acidic strength is : B > A > C.

7. Antacids are mild non-corrosive bases which are used to neutralise the excess acidity inthe stomach, e.g., sodium hydrogencarbonate (NaHCO3) and milk of magnesia [Mg(OH)2].

WORKSHEET-59

1. Acidic salts : AlCl3, ZnSO4, CuSO4

Basic salts : CH3COONa, NaHCO3, Na2CO3

Neutral salts : NaCl, KNO3

2. (a) On heating gypsum at 373 K, it loses its water molecules and gets converted into plasterof Paris.

(b) On mixing plaster of Paris with water,it changes into gypsum again.

3. ! Take about 1 g solid NaCl in a clean anddry test tube and set up the apparatusas shown in the figure.

! Add some concentrated sulphuric acidto the test tube.

! We will observe that a pungent smellinggas (HCl) is evolved.

! Test the gas evolved with dry and wetblue litmus paper.

! We will observe that their is no effect ondry blue litmus paper while the moist blue litmus paper turns red indicating that dry HClgas does not show acidic character whereas HCl solution is acidic.


4. (a) When baking soda is used for baking purposes, on heating at high temperature it decomposesand evolves carbon dioxide gas. This carbon dioxide gas evolved helps the cake to rise andmakes it soft and spongy.

(b) Sodium bicarbonate is used in soda-acid fire extinguisher. It reacts with acid to evolve,carbon dioxide gas which is a non-supporter of combustion and is heavier than air. Thus, itsettles on the burning substance and cuts off the supply of oxygen and extinguishes it.

2NaHCO3 + H2SO4(aq) → Na2SO4 + 2CO2↑ + 2H2O

(c) Its pH is more than 7.

5. pH is a number which indicates the acidic or basic nature of the solution. The pH of asolution is expressed in terms of hydrogen ion concentration. Higher is the hydrogen ionconcentration, lower is the pH.

pH of a neutral solution is 7. pH of an acidic solution is less than 7 and lies between 1-7while pH of a basic solution is greater than 7 and lies between 714.

6. The strength of an acidic or basic solution depends on the number of H+ ions and OH ionsproduced. Higher is the concentration of the H + ions, more acidic is the solution and viceversa. Similarly higher is the concentration of OH ions, more basic is the solution. Thiscan be done by measuring the pH of the solution. If the pH of the solution is less than 7, itis acidic in nature and if the pH of the solution is more than 7 it is basic in nature.

7. Metallic oxide is basic in nature.

Take a small piece of magnesium ribbon and burn it in air. White powder of magnesiumoxide is formed. Dissolve this white powder in water by heating. Now check it with bothred and blue litmus papers. We will observe that red litmus turns blue indicating thatmetallic oxides are basic oxides.

2Mg + O2 ∆→ 2MgO

MgO + H2O → Mg(OH)2

8. The reaction of granulated zinc with dilute HCl will be faster than that with dilute aceticacid. This is because HCl being a stronger acid will furnish greater concentration of H+ ionsas compared to CH3COOH which is a weaker acid.

Zn + 2HCl (aq) → ZnCl2 + H2↑

Zn + 2CH3COOH (aq) → (CH3COO)2 Zn + H2↑

WORKSHEET-60

1. (a) Plaster of Paris is manufactured by the controlled heating of gypsum at 373 K.

CaSO4.2H2O 373K∆→ CaSO4.

12

H2O + 112

H2O

Gypsum Plaster of Paris

(b) CaSO4.12

H2O + 112

H2O → CaSO4.2H2O

Plaster of Paris Gypsum

Mixing of plaster of Paris with appropriate quantities of water results into formation ofhard mass called gypsum.

40 XS C I E N C E

(c) 1. It is used to set the fractured bones in right position.

2. It is used for making toys.

(d) In plaster of Paris, there are two formula units of calcium sulphate that share one molecule

of water, i.e., (CaSO4)2.H2O. Hence, one formula unit will have 12

molecule of water and is

written as CaSO4. 12

H2O.

2. (a) The colour of copper sulphate crystals is blue before heating.

(b) Copper sulphate crystals contain water of crystallisation. When we heat the crystals, thiswater is removed and the salt turns white.

(c) When 2 or 3 drops of water is added to the crystals, they become blue again.

(d) CuSO4.5H2O ∆→ CuSO4 + 5H2O

(Blue) (White)

CuSO4 + 5H2O → CuSO4.5H2O

(White) (Blue)

3. (a) On conversion of milk into curd, its pH will decrease and will become less than 6. The pHdecreases as curd is more acidic than milk due to the presence of lactic acid. More acidic isthe substance, lesser is its pH.

(b) (i) Milk is acidic in nature and turns more acidic and is sour to taste if kept for few hours,due to the formation of lactic acid. To prevent the formation of lactic acid and spoilingof milk, baking soda is added. Baking soda being alkaline in nature prevents it tobecome more acidic.

(ii) This is due to the presence of baking soda in milk which is alkaline in nature andprevent the milk from turning into lactic acid which is present in curd and thus, delaysits setting.

(c) 1. It is used as an ingredient in antacids.

2. It is used in soda-acid fire extinguishers.

(d) Sodium hydrogencarbonate is an essential ingredient in antacids due to its alkalinenature. Being alkaline, it neutralizes excess acid in the stomach and provide relief.

WORKSHEET-61

1. (a) Solution D with pH7 is neutral.

(b) Solution C with pH11 is strongly alkaline.

(c) Solution B with pH1 is strongly acidic.

(d) Solution A with pH4 is weakly acidic.

(e) Solution E with pH9 is weakly alkaline.


2.

Aim: To show that hydrochloric acid solution conducts electric current.

Materials Required: 100 ml beaker, 6 volt battery, bulb, switch, rubber corks, dilutehydrochloric acid.

Procedure: Fix two nails on the corks and connect the nails to the two terminals of the 6 Vbattery through a bulb and a switch as shown in the figure.

Now pour about 50 ml of dilute hydrochloric acid in the beaker and switch on the current.

We will observe that bulb starts glowing indicating that the solution conducts electric current.

Conclusion: Aqueous solution of hydrochloric acid conducts electricity due to the presenceof ions which conduct electricity.

WORKSHEET-62

1. (a) 2. (d ) 3. (a) 4. (c) 5. (b) 6. (d) 7. (a) 8. (b) 9. (a) 10. (a)

11. (a) 12. (d) 13. (c) 14. (b) 15. (b) 16. (b) 17. (b) 18. (d) 19. (c)

WORKSHEET-63

1. (b) 2. (b ) 3. (d) 4. (c) 5. (c) 6. (b) 7. (b) 8. (d) 9. (c) 10. (b)

11. (c) 12. (a)

WORKSHEET-64

1. (d) 2. (b ) 3. (b) 4. (b) 5. (d) 6. (b) 7. (a) 8. (a) 9. (c) 10. (c)

1. (c) 2. (b)

3. The concentration of OH ions increases in the solution.

4. (a) Water of crystallisation is the fixed number of water molecules present is one formula unitof the salt, e.g., ferrous sulphate (FeSO4. 7H2O) has 7 molecules of water of crystallisation.

(b) Copper sulphate crystals are associated with 5 molecules of water of crystallisation andare blue is colour. On heating, they lose 5 molecules of water of crystallisation and thusturn white.

42 XS C I E N C E

5. (a) CaSO4. ½ H2O

(b) CaSO4.2H2O 373 K∆→ CaSO4.

12 H2O + 3

2 H2O

(c) It is used in hospitals for setting fractured bones in the right position.

6. (a) NH4Cl, (NH4)2SO4, MgCl2.

(b) Zinc being more reactive than hydrogen can displace hydrogen from acids but nitric acidis a strong oxidising agent and thus the hydrogen gas evolved is oxidised to water.

7. Take solutions of glucose, alcohol, HCl and H2SO4. Place the cork with fixed two nails in 100 mLbeaker. Connect the nails to the two terminals of a 6 volts battery through a bulb and aswitch. On pouring dil. HCl and H2SO4 in the beaker in the state of flowing current, we seebulb will start glowing. On the other hand, glucose and alcohols do not conduct electricitywhen above process would be applied with both of them.

8. (a) Gas evolved at cathode is hydrogen and at anode is chlorine.

(b) Uses: Hydrogen is used in the manufacture of fertilizer such as ammonia. Chlorine isused in the manufacture of PVC.

(c) 2NaCl (aq) + 2H2O (l) 2NaOH (aq) + Cl2(g) + H2(g)

9. (a) Sodium bicarbonate (NaHCO3) and its common name is baking soda.

(b) This is because it is a mild base and can thus neutralise excess acid in the stomach.

(c) X can react with sulphuric acid in the fire extinguisher and release carbon dioxide gaswhich is heavier than air and non-supporter of combustion and thus can extinguish fire.

(d) No, we cannot make use of baking soda, because decomposition of it. On heating, itproduces sodium carbonate which will make the cake taste bitter.

43M E T A L S A N D N O N M E T A L S

WORKSHEET-691. (d) Iodine 2. (c) Calcium3. (b) Silver 4. (d) All of these5. (b) Gallium 6. (c) Diamond7. (b) Basic 8. (d) Al2O3

9. (b) Copper 10. (b) Magnesium11. (b) Hydrogen 12. (c) Silver13. (c) Aluminium 14. (c) Molten state15. (b) Gangue 16. (b) Cu and Zn17. (b) Carbonate ores 18. (a) Sulphide ores19. (c) Using carbon 20. (d) Mercury21. (d) AgNO3 solution and copper metal 22. (c) Applying a coating of zinc23. (c) Silver sulphide 24. (c) Copper carbonate25. (d) Pure metal is made the anode 26. (a) Calcium

WORKSHEET-701. (c) Zinc is more reactive than tin 2. (a) Blue to green3. (b) Fe2O3 + 2Al → 2Fe + Al2O3 4. (b) Electrolytic reduction5. (c) Cinnabar 6. (b) Oxides7. (c) Sodium chloride 8. (b) Al < Cu < Ag9. Sodium and potassium 10. Gold and silver

11. Gold and silver12. The property of the metal by virtue of which it can be beaten into thin sheets upon

hammering is called malleability.13. It is the ability of the metals to be drawn into thin wires.14. Acidic oxide: carbon dioxide, sulphur dioxide

Basic oxide: calcium oxide, magnesium oxideAmphoteric: aluminium oxide, zinc oxide

15. An alkali is a highly soluble base in water. Those bases that dissolve easily in water formalkalies.Examples: Sodium hydroxide (NaOH), potassium hydroxide (KOH)

16. Sodium and potassium17. Hydrogen18. Hydrogen19. A mineral is a naturally occurring inorganic substance with a definite chemical composition

whereas, an ore is a mineral from which a metal is extracted profitably and economically.20. Gold and platinum

6 METALS AND NON-METALS

44 XS C I E N C E

WORKSHEET-711. (a) Aluminium and copper

(b) Silver and copper(c) Lead and mercury(d) Liquid metal: Mercury

Liquid non-metal: Bromine(e) Gallium and caesium( f ) Iodine(g) Graphite(h) Lithium and sodium(i) Gallium and caesium(j) Gold(k) Gold, platinum and silver

2. Reduction3. Oxides and sulphides4. Roasting5. Calcination6. A moderately reactive metal oxide is converted into metal by the process of reduction, using

coke as a reducing agent.7. Aluminium, calcium8. Al is getting oxidised to Al2O3.

MnO2 is getting reduced to Mn.9. Electrolytic reduction

10. Electrolytic refining11. The two important conditions necessary for the process of corrosion to take place are:

(a) Presence of air, (b) Presence of moisture12. Stainless steel is composed of iron, chromium and nickel.

WORKSHEET-721. The important methods to prevent rusting of iron are:

Painting, oiling, greasing, galvanising, chrome plating and alloying.2. An amalgam is an alloy in which one of the metals is mercury.3. 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g).4. Alloys are homogeneous mixture of a metal with a metal or a non-metal.5. Metals which displace hydrogen from dilute acids are: calcium, magnesium.

Metals which do not displace hydrogen from dilute acids are: copper, silver.6. Sodium and potassium.7. Zinc.8. Gold and platinum.9. A reaction between aluminium and iron oxide to produce aluminium oxide and iron with

the liberation of heat energy and producing iron in molten state is called thermite reaction.2Al + Fe2O3 → Al2O3 + 2Fe + Heat


10. Bauxite, Al2O311. Alloys do not get oxidised or burn readily at high temperature. Thus, they are used in

electrical heating devices.12. Large amount of unwanted impurities such as soil, sand etc., associated with the ore are

collectively called gangue.13. 24 carat gold is extremely soft gold and is thus, not suitable for making jewellery. 22 carat

gold is used, as it is hard. Gold is alloyed with Ag or Cu to make it hard.14. Pure iron is extremely soft and stretches easily when hot. On mixing smaller amount of

carbon (0.05%), it becomes hard and strong.15. Magnesium and manganese16. Mercury(Hg) is the only metal that exists in liquid state at room temperature.

17. (a) 3Fe + 4H2O → Fe3O4 + 4H2↑

(b) Ca + 2H2O → Ca(OH)2 + H2↑

2K + 2H2O → 2KOH + H2↑

(c) Na2O + H2O → 2NaOH

(d) 2Cu + O2∆→ 2CuO

WORKSHEET-731. Alloys are made by mixing the metals in their molten state. It is prepared by first melting

the primary metal and then dissolving the other metal in definite proportions. It is thencooled to room temperature.

2. Electric wires are made up of metals, which are good conductors of electricity. To preventelectric shock on touching them, they are coated with polyvinyl chloride which is a badconductor of electricity.

3. Those metal oxides which can react with both acids as well as bases to produce salt andwater are called amphoteric oxide, e.g., Al2O3 and ZnO. Al2O3 can react with both acid(HCl) and base (NaOH) as shown below:

Al2O3 + 2NaOH → 2NaAlO2 + H2O;Al2O3 + 6HCl → 2AlCl3 + 3H2O

4. Baking powder is a mixture of baking soda and tartaric acid. When cake is baked in a oven,due to the high temperature in the oven baking soda (NaHCO3) decomposes and carbondioxide gas is evolved. This gas evolved makes the cake soft and spongy.

2NaHCO3 ∆→ Na2CO3 + CO2 + H2O

5. Sodium metal is a highly reactive metal which vigorously reacts with oxygen present in airif kept in open and catches fire. Thus, to prevent its reactivity and prevent accidental fires itis kept immersed in kerosene oil.

6. Aluminium and zinc are reactive metals which on exposure to air form an oxide layer on itssurface. This oxide layer acts as a protective layer and prevents the metal beneath its surfacefrom oxidation.

7. Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal.Fe + H2SO4(aq) → FeSO4 + H2↑

8. Copper metal is used for making electric wires as it is:

(a) good conductor of electricity. (b) highly ductile, so it can be drawn into wires.

46 XS C I E N C E

9. Calcium and magnesium. Calcium and magnesium react with hot and cold water to evolvehydrogen gas. The bubbles of the gas evolved stick to the surface of the metal and thus,being lighter floats on the surface.

10. Sodium and potassium. Sodium and potassium are highly reactive metal which reactvigorously with cold water to evolve hydrogen gas. The reaction is highly violent andexothermic and the evolved gas catches fire.

11. Nitric acid is a strong oxidising agent. Thus, when a metal reacts with nitric acid, the H2 gasproduced is oxidised to water by nitric acid and it itself gets reduced to any of the oxides ofnitrogen (NO2, N2O).

WORKSHEET-741. It is a series of metals in which the metals are arranged in a vertical column in the

decreasing order of their reactivity. Potassium the most reactive metal is placed at the topwhile gold the least reactive metal is placed at the bottom.

2. (a) Hydrogen, (b) Downward displacement of water, (c) Insoluble in water, (d) Lighter than air.3. (a) Copper

(b) Iron(c) Manganese(d) Copper

4. When a piece of granulated zinc is added to ferrous sulphate solution, the colour of solutionchanges from green to colourless and the surface of zinc metal becomes dull and black. Zincbeing a more reactive metal displaces iron from its salt solution and due to formation of zincsulphate the solution turns colourless.

Zn + FeSO4 → ZnSO4 + FeType of reaction: Displacement reaction.

5. Ionic compounds consist of positive and negative ions which are held together strongly dueto strong force of attraction between the oppositely charged ions. Thus, large amount of heatenergy is required to overcome interionic interaction raising its melting point.

6. The condition required for the conduction of electricity in the presence of free ions/electrons.In solid state the ions are held tightly while in molten state the heat energy overcomes theelectrostatic forces of attraction between the oppositely charged ion. Thus, ions move freelyand conduct electricity. In aqueous solution also the ionic compound in water contain ionsto conduct electricity.

7. Ionic compounds consist of oppositely charged ions which are held strongly to each otherby electrostatic forces of attractions and thus the compound exists as solid and becomeshard and brittle.

8. Metal sulphides and carbonates are converted into metal oxide prior to reduction because itis easier to extract metal from its oxide form than from any other form of the ore.

WORKSHEET-751. Carbonate ores are calcined, i.e., they are heated in the absence of oxygen to convert into

their oxide form, e.g.

ZnCO3 ∆→ ZnO + CO2

Carbonate ore of zinc gets converted into its oxide form on calcination.


2. Roasting is a process of heating an ore in sufficient supply of oxygen to convert into theiroxide form. Sulphide ores are roasted to convert into their oxide form, e.g.

2ZnS + 3O2 ∆→ 2ZnO + 2SO23. Reaction between aluminium metal and iron oxide producing aluminium oxide and iron

metal in molten state due to exothermic nature of the reaction is called thermite reaction.2Al + Fe2O3 → Al2O3 + 2Fe + Heat

Application: Molten iron obtained is used to join railway tracks or cracked machine parts.4. (a) Carbon cannot be used to reduce the oxides of highly reactive metals, as highly reactive

metals are highly stable and have more affinity for oxygen than carbon. Thus, carboncannot reduce them.

(b) Highly reactive metals such as sodium, calcium, aluminium can be used as reducingagents as they can displace metals of lower reactivity from their compounds, e.g.

3MnO2 + 4Al → 3Mn + 2Al2O3 + Heat

5. Roasting

1. Roasting is a process of heating an ore inthe presence of oxygen.

2. It is used to convert the sulphide ore totheir oxide form, e.g.,

2ZnS + 3O2 → 2ZnO + 2SO2

Calcination

1. Calcination is a process of heating anore in the absence of oxygen.

2. It is used to convert carbonate ore intotheir oxide form, e.g.,


6. Acidic oxides are formed by the combination of non-metal with oxygen. A non-metallicoxide on dissolution in water forms acid that turns blue litmus red indicating its acidicnature, e.g.,

C + O2 → CO2

CO2 + H2O → H2CO3

(Carbonic acid) → turns blue litmus red.

7. Platinum, gold and silver are used to make jewellery because of the following reasons:(a) They are highly lustrous metals which are resistant to corrosion.(b) They are highly malleable and ductile, so can be transformed into any shape/design.

8. Aluminium metal although a highly reactive metal is used for making cooking utensilsbecause aluminium on exposure to air forms a thin layer of oxide (Al2O3) on its surface whichacts as a protective layer and prevents the metal beneath its surface from further oxidation.

9. Copper is used to make hot water tanks and not steel because copper is a better conductorof heat than steel.

10. Chemical formula of washing soda is Na2CO3.10H2O.It is obtained from baking soda by first heating it strongly which gives sodium carbonateand then followed by the recrystallization of sodium carbonate which gives washing soda.

2NaHCO3Heat→ Na2CO3 + CO2 + H2O

Baking soda Sodium carbonate

Na2CO3 + 10 H2O → Na2CO3.10H2OWashing soda

Industrial use: It is used for softening of hard water.

48 XS C I E N C E

WORKSHEET-761. (a) Bronze metal is an alloy of copper and tin.

(b) It is because of the corrosion of copper metal that it turns green. The green colour is due tothe formation of basic copper carbonate.

2. The electrostatic force of attraction that holds the oppositely charged ions together in acompound is called ionic bond, e.g., ionic bond is formed between sodium ion and chlorideion in sodium chloride.

+ → Na+ :Cl:−⋅⋅

⋅⋅

(2, 8, 1) (2, 8, 7)3. Sodium (Na) 11Na2, 8, 1

Oxygen (O) 8O 2, 6

Magnesium (Mg) 12Mg2, 8, 2

4. (a) Sodium oxide:

11Na 2, 8, 1; 8O 2, 6

Na. + O::

: → Na+2

O::

::2

Na2O

Na.

Magnesium oxide:

12Mg 2, 8, 2; 8O 2, 6

Mg: + O::

: → Mg O:

:

::2+ 2

→ MgO

(b) The ions present in sodium oxide are: (Na+) and (O2)Sodium ion Oxide ion

The ions present in magnesium oxide are: (Mg2+) and (O2)Magnesium ion Oxide ion

5. Sodium chloride: 11Na 2,8,1Na → Na+ + e

(2,8,1) (2,8)Cl + e → Cl

(2,8,7) (2,8,8)Na+ + Cl → NaClCalcium oxide: 20Ca 2,8,8,2Ca → Ca2+ + 2e

(2,8,8,2) (2,8,8)O + 2e → O2

(2,6) (2,8)Ca2+ + O2 → CaO

Na.

Cl. :. .. .


6. In the electrolytic refining of metal M, impure metal M acts as an anode, pure metal M actsas a cathode while the soluble salt of metal M acts as an electrolyte.

7. Sodium, potassium and lithium are highly reactive metals which react vigorously with oxygen andwater to evolve hydrogen gas. The reaction is highly violent and exothermic and so the evolved gascatches fire. Thus, to prevent its reactivity with oxygen and water, it is stored under oil.

8. Copper metal slowly reacts with water, carbon dioxide and oxygen present in air to formbasic copper carbonate which is green in colour and gets deposited on the surface of metal.Lemon juice and tamarind contain weak acids which reacts with basic copper carbonate toform soluble salts. The salts gets removed and the metal restores its shine.

WORKSHEET-771. (a) (i) There will be no effect on dry litmus paper.

(ii) Moist litmus paper will turn red due to the formation of sulphurous acid.(b) S + O2 → SO2

SO2 + H2O → H2SO3

2. Sodium → Na. Chlorine →

(11Na 2,8,1) (17Cl 2,8,7)They form a bond by a complete transfer of electron from sodium to chlorine atom as shownbelow:

Na• + Cl::

:. → Na+ :

:

::

Cl

(2,8,1) (2,8,7)The bond formed is called Ionic/Electrovalent bond. The compound formed has highmelting point as it consists of sodium ion and chloride ion which are held strongly by theelectrostatic forces of attraction. Thus, a large amount of heat energy is required to break theinter-ionic attraction resulting in high melting point.

3. (a) By heating alone, e.g.

2HgS + 3O2 ∆→ 2HgO + 2SO2(Cinnabar) 2HgO ∆→ 2Hg + O2

(b) By using coke as reducing agent. Sometimes reactive metals such as Na, Mg and Al canalso be used.

(c) Oxides of highly reactive metals are subjected to process of electrolytic reduction.

4. Metals Non-metals

1. Metals react with oxygen to form 1. Non-metals react with oxygen to formoxides which are basic in nature. oxides which are neutral or acidic.

2. Active metals displace hydrogen from 2. Non-metals do not displace hydrogendilute acids. from dilute acids.

3. Active metals displace hydrogen from 3. Non-metals do not displace hydrogenwater. from water.

4. Metals are electropositive in nature 4. Non-metals are electronegative in nature(electron donars). (electron acceptors).

50 XS C I E N C E

5.

For an electrolytic refining of metal MAnode : Impure metal MCathode : Pure metal MElectrotyte : Solution of soluble salt of metal M

6. Alloys are homogeneous mixture of a metal with a metal or a non-metal.An alloy is generally preferred to pure metal because of the following properties:(1) Alloys are generally harder than the pure metal, e.g., gold is extremely soft metal but

when alloyed with Ag/Cu becomes hard.(2) They are corrosion resistant. e.g. stainless steel an alloy of iron, carbon, chromium and

nickel does not get corroded and the lustre lasts longer.(3) They have low melting points than the pure metals, e.g., solder an alloy of lead and tin

has a much lower melting point than pure metals.

WORKSHEET-781. Distinction between metals and non-metals:

(a) (i) Using a hammer. We can distinguish between metals and non-metals as metals willform thin sheets upon hammering while non-metals do not.

(ii) Using a bulb, wire, battery and switch. Set up the apparatus as shown in the figure.On inserting a metal wire (say copper) between the clips A and B the bulb glowswhile inserting a non-metal (sulphur powder) the bulb does not glow.Conclusion. Metals conduct electricity while non-metals do not.

(b) The above tests can be used to distinguish between metals and non-metals exception:Hammering can not be used for soft metals like Na and K. Also, graphite a non-metalconducts electricity.

2. Use Alloy

(i) For soldering joint solder(ii) For cutlery Stainless steel

(iii) For aircraft parts Duralumin(iv) For making statues Bronze(v) For surgical instruments Stainless steel

3. (a) No, we cannot store copper sulphate solution in a vessel made up of zinc, as zinc is amore reactive metal than copper and will displace copper from its salt solution. This willresult into the formation of holes into the container.


(b) On adding zinc to ferrous sulphate solution, we will observe that after some time thelight green colour of ferrous sulphate solution fades away and the surface of zincbecome dull and black. A more reactive metal zinc displaces iron from its salt solution.

Zn + FeSO4(aq) → ZnSO4(aq) + Fe4. The solution used was aqua regia which consists of 3 parts of concentrated hydrochloric

acid and one part of conc. nitric acid. It is able to dissolve gold and thus the weight of thegold ornaments decreases. Since the outer layer of gold gets dissolved, the bangles sparklelike new but the weight decreases.

5. (a) Those metal oxides which show both acidic as well as basic behaviour are calledamphoteric oxides. They react with both acids as well as bases to produce salt and water.Amphoteric oxides: Al2O3, ZnO.

(b) Non-metals do not displace hydrogen from dilute acids as they have 5, 6 or 7 valenceelectrons and are themselves electron acceptors. Thus, they cannot provide electron toH+ of acid to convert it into hydrogen gas.

6. (i) This is because zinc is more reactive than copper and thus, will displace copper fromits salt solution.

(ii) This occurs due to phenomenon of corrosion. Silver metal reacts with sulphurcompounds present in air to form silver sulphide which is black.

(iii) A metal sulphide is converted to its oxide form as it is easy to extract metal from itsoxide form than from its sulphide ore.

WORKSHEET-791. Iron is more reactive than copper. Thus, when iron is immersed in copper sulphate solution,

it displaces copper from its salt solution and forms Iron sulphate which is green in colour.Thus, due to the displacement reaction taking place, colour change is observed.

Fe + CuSO4(aq) → FeSO4(aq) + CuBlue Green

2. (a) Corrosion is useful in case of metals such as Al, Zn, Mg. These metals form a thin layerof oxide on exposure to air, which acts as a protection layer and prevents the metalbeneath its surface from corrosion.

(b) Iron is a metal that is highly prone to rusting. On exposure to moist air, a reddish brownpowdery substance is formed on its surface called rust and metal gets wasted away layerby layer.

3. Galvanization is a process of protecting iron metal from rusting by coating it with a layer ofzinc, by dipping it in molten zinc.Application: Iron pipes carrying water are generally galvanised to protect it from rusting.These pipes are called as GI pipes (Galvanised iron).

4. Reaction (i) is possible, as Zn is more reactive than copper and thus, displaces it from its saltsolution.Reaction (ii) is not possible as iron is less reactive than zinc so it can not displace zinc fromits salt solution.Reaction (iii) is possible as Zn is more reactive than iron. Zn thus, displaces iron from its saltsolution (FeSO4).

5. (a) Oxide formed is amphoteric in nature.(b) The metal X is zinc and the formula of its oxide is ZnO.(c) ZnO + 2HCl → ZnCl2 + H2O

ZnO + 2NaOH → Na2ZnO2 + H2O

52 XS C I E N C E

6. (a) ! Set up the apparatus as shown in the figure.! Place the metal to be tested in the circuit between terminals A and B.! We will observe that the bulb glows indicating that metals are good conductors of

electricity.

(b) (i) Nitric acid is a strong oxidising agent. Thus, when a metal reacts with nitric acid,the H2 gas produced is oxidised to water by nitric acid and it itself gets reduced toany of the oxides of nitrogen (NO2, N2O).

(ii) Sodium metal is a highly reactive metal which vigorously reacts with oxygenpresent in air if kept in open and catches fire. Thus, to prevent its reactivity andprevent accidental fires it is kept immersed in kerosene oil.

(iii) The reaction of Fe2O3 with aluminium is a highly exothermic reaction. In thisreaction, aluminium reduces iron oxide to produce iron metal with the evolution oflot of heat. Due to this heat, iron metal is produced in molten state. The molten ironis poured between the broken iron pieces to join them.

WORKSHEET-801. (a)

In this method the impure copper metal is made the anode and a thin strip of pure metal ismade the cathode. A solution of the metal salt, i.e., copper sulphate is used as an electrolyte.On passing electric current through the electrolyte, Cu2+ ions from the anode dissolves intothe electrolyte and an equivalent amount of Cu from the electrolyte is deposited on thecathode.Reaction at cathode: Cu2+ + 2e → CuReaction at anode: Cu → Cu2+ + 2e (Oxidation)(b) It is the insoluble impurities which settles at the bottom of the anode during electrolytic

refining.(c) (1) It is used for making electrical wires as it is highly ductile and good conductor of heat.

(2) Being good conductor of heat, it can be used for making utensils.


2. (a) 3Fe + 4H2O ∆→ Fe3O4 + 4H2(Red hot) (Steam)

(b) Al2O3 + 2NaOH → 2NaAlO2 + H2O(c) K2O + H2O → 2KOH(d) Zn + 2HCl (aq) → ZnCl2 + H2↑

(e) 4Fe + 3O2 ∆→ 2Fe2O3

3. (a) Silver metal when exposed to atmospheric conditions reacts with sulphur compoundspresent in air to form a black coating of silver sulphide on its surface. Thus, it gets tarnished.

(b) Zinc being a more reactive metal than copper displaces copper from its salt solution andforms zinc sulphate. Due to the formation of zinc sulphate the blue colour fades away.

Zn + CuSO4(aq) → ZnSO4(aq) + Cu(c) Bells are made up of metals, as metals are sonorous in nature, i.e., they produce a ringing

sound on striking a hard surface.(d) Ionic compounds consist of oppositely charged ions which are held firmly by the strong

electrostatic forces of attraction between their ions, making them exist in crystalline form(solids).

(e) Highly reactive metal oxides are extremely stable. They have more affinity for oxygenthan carbon. Thus, carbon cannot reduce them.

WORKSHEET-811. (a) Due to the process of corrosion, metals acquire dull surface on exposure to moist air.

(b) The important conditions necessary for the process of rusting to take place are:(i) Presence of oxygen/air (ii) Presence of moisture.

(c)

Observation. After few days we will observe that iron nails in test tube A form a reddishbrown coat on its surface, which is called rust, while iron nails in test tube B and Cremain free from rust.Conclusion. Presence of both air and water is necessary for the process of corrosion.

(d) 1. By application of paint/oil or grease on the surface of metal.2. By galvanization of iron.

54 XS C I E N C E

2. (a) Displacement reaction.(b)

Aim. To show that iron is more reactive than copper.Requirements. Iron nail, copper wire, copper sulphate solution, iron sulphate solution,test tubes, test tube stand.Method. Dip an iron nail in copper sulphate solution and a copper wire in iron (II)sulphate solution and wait for some time.Observation. The colour of copper sulphate solution changes from blue to green and areddish coat is seen on the iron nail while no change takes place in iron sulphate solution.Conclusion. Iron is more reactive than copper and thus displaces it from its salt solution.

(c) In a displacement reaction a more reactive metal displaces a less reactive metal from itssalt solution, e.g.,

Zn + CuSO4(aq) → ZnSO4(aq) + Cuwhile in a double displacement reaction their is an exchange of ions between thereactants, e.g.


WORKSHEET-82

1. (a) ZnCO3 (Ore of zinc)

Concentration of ore

Calcination (Conversion of ore to oxide form)ZnCO3

∆→ ZnO + CO2

Oxide ore of the metal

Reduction using coke as reducing agentZnO + C → Zn + CO

Purification of metal


(b) Cinnabar ore(HgS)


Roasting (Conversion of ore into oxide form)2HgS + 3O2 ∆→ 2HgO + 2SO2

2HgO ∆→ 2Hg + O2

Mercury metal

Refining

WORKSHEET-83

1. (d) 2. (b) 3. (c) 4. (d) 5. (d) 6. (d)7. (c) 8. (d) 9. (b) 10. (d) 11. (d)

WORKSHEET-841. (a) 2. (c) 3. (b) 4. (b) 5. (b) 6. (d)7. (c) 8. (a)

1. (d) 2. (b)3. For an electrolytic refining of metal M

Anode : Impure metal MCathode : Pure metal M

Electrolyte : Solution of soluble salt of metal M.4. (a) On adding zinc to ferrous sulphate solution, we will observe that after sometime the light

green colour of ferrous sulphate solution fades away and the surface of zinc become dulland black. A more reactive metal zinc displaces iron from its salt solution.

(b) Single displacement reaction.5. (a) (b)

56 XS C I E N C E

6. (a) Reaction between aluminium metal and iron oxide producing aluminium oxide and ironmetal in molten state due to exothermic nature of the reaction is called thermite reaction.

2Al + Fe2O3 Al2O3 + 2Fe + Heat

(b) Application. Molten iron obtained is used to join railway tracks or cracked machine parts.7. (a) Although, silver is a noble metal, yet it reacts with sulphur compounds present in air to

form silver sulphide which is black in colour and gets tarnished.(b) Carbonates and sulphide ores are usually converted into metal oxide prior to reduction

because it is easier to extract metal from its oxide form than from any other form of the ore.(c) The presence of free ions/electrons shows the property of conduction of electricity. In

solid state, ions are held tightly result in not move freely and also not conduct electricity.8. (a) Metal M is reduced using coke, e.g., haematite, an ore of iron, is reduced using coke.

Fe2O3 + 3C 2Fe + 3CO(b) Metal N which is high up in the reactivity series, is separated from its chlorides by

electrolytic reduction, e.g., sodium is obtained at cathode by the electrolytic reduction ofmolten sodium chloride.

9. (a) Carbonate ore.(b)

ZnCO3 (Ore of zinc)


Calcination (Conversion of ore to oxide form)



Reduction using coke as reducing agent

ZnO + C → Zn + CO

Purification of metal

(c) 2HgS (s) + 3O2(g) Heat→ 2HgO + 2SO2(g)

2HgO (s) Heat→ 2Hg(l) + O2(g)


BIOLOGY

58 XS C I E N C E

WORKSHEET-891. (d) All of these 2. (b) Lipase

3. (a) Trypsin 4. (c) Excretion

5. (a) Transport of water 6. (b) Mitochondrion

7. (b) Capillaries 8. (b) Two chambers

9. (b) Mucus 10. (b) Breakdown of starch into sugars

11. (c) Absorb carbon dioxide 12. (a) Right ventricle

13. (c) Transpiration 14. (a) Clotting

15. (b) Yeast, mushroom, bread mould

16. (c) They convert CO2 and water into carbohydrates in the absence of sunlight.

17. (a) Heterotrophs do not synthesise their own food.

18. Nutrition, respiration, excretion, growth, reproduction.

19. Maintenance processes like nutrition, respiration, excretion, growth, reproduction needed tosustain and maintain life by preventing damage and keeping the body in a healthy state.

20. Veins.

21. Starch and O2.

22. Fungus derives its nutrition either by parasitic or saprophytic manner while tapeworm isonly parasitic.

23. Starch and glycogen.

24. (a) Fungisaprophytic (b) Amoebaanimal like

25. Small intestine is the longest part, 6 metres long.

26. Transpiration. Loss of excessive water through evaporation from the aerial parts of theplant like leaves.

27. Translocation.

28. Water reabsorption occurs through villi, undigested food is stored in rectum and thrown outthrough anus. Exit is regulated by anal sphincter.

WORKSHEET-901. Saliva contains enzyme amylase which breaks down starch to maltose.

2. Birds and mammals have high energy needs as they need energy to maintain a constantbody temperature (warm blooded animals or endotherms).

3. The mechanism by which organisms obtain O2 from environment and release CO2.

4. Phloem.

5. Cytoplasm.

6. It occurs through the pores-stomata on the leaves as well as through the surface of stem,roots and leaves.

7 LIFE PROCESSES

59L I F E P R O C E S S E S

7. C6H12O6 → pyruvate → 2C2H5OH + 2CO2 + Energy Glucose Ethyl alcohol Carbon

dioxide

8. Leaves of green plants prepare the food which is needed in all parts of plants, including roots.This food has to be transported to all parts of the plants in the dissolved formtranslocation.

9. Water, urea, uric acid, salts.10. Glomerulus.11. Water and minerals dissolved in it move up to leaves from root through tracheids and

vessels which are two kinds of elements of xylem.12. Xylem.13. Transpiration: loss of water in vapour form from leaves of plants.

Due to transpiration, deficit of water is created in the leaves pulling water and mineralsupwards through xylem elementsascent of sap.

14. Autotrophs obtain CO2 from atmosphere through diffusion. Plants have stomata to take it in. N2cannot be taken in as by the autotrophs. Plants can absorb it in the form of nitrates and nitrites.

15. 6CO2 + 12H2O light

Chlorophyll→ C6H12O6 + 6H2O + 6O2

Glucose

16. The breakdown of food in cells to release energy. All kind of food is broken down throughoxidation-reduction reaction and its chemical energy is converted into a universal source ofchemical energyATP, Adenosine Tri Phosphate.

17. Contraction and expansion of alimentary canal to push the food forward.18. ATP, Adenosine Tri Phosphate.19. Glycolysis.20. Digestive enzymes breakdown complex molecules of food into simpler ones so that they can

be absorbed by blood.21. Aerobic respiration and anaerobic respiration.22. They are chemically proteinaceous biocatalysts, which increase or decrease the rate of a

biochemical reaction.23. Iodine in salt helps in making the hormone thyroxin by thyroid gland. It not only prevents

the disease goitre but also helps in regulating metabolism of carbohydrates, fats and proteins.24. Anaemia.25. It occurs in chloroplasts in palisade cells or tissues in green parts of leaves in plants.26. It kills germs in food and provides acidic medium for the action of pepsin enzyme to digest

the proteins in stomach.WORKSHEET-91

1. Energy is needed to carry out all life processes. Living beings use carbon based (organic) moleculesfrom their surroundings to derive energy, though some of them can prepare them from inorganiccompounds. They also use them for growth, reproduction and repair in their body.

2. No, the plant will not stay healthy for a long time. The reasons are:(a) It will not be able to exchange O2 and CO2, hence respiration will be affected adversely.

(b) Photosynthesis will also be affected as CO2 will not be available.

(c) Transpiration will not take place hence, there will be no ascent of sap, hence no waterabsorption from the soil.

60 XS C I E N C E

3. The transport system of an animal moves substances to where they are needed in the body.Even the smallest animal must have the means of transporting substances around its body.Oxygen and food molecules must move to all the cells, and the waste products must beremoved from the cells and expelled into the environment. It occurs through diffusionmainly.

In a multicellular organism, all cells are not in contact with the surroundings hence, diffusionwill be insufficient for it. A variety of fluid systems, called vascular systems, help suchtransport in most members of the animal kingdom.

4. Amount of O2 dissolved in water is less than O2 present in air. Therefore, rate of breathingin aquatic animals is faster than that in terrestrial animals.

5. Translocation. Transport of organic food from the leaves to the other parts of the plantsthrough the sieve tubes of phloem tissue is called translocation.

Importance. It is an essential process as every part of the plant requires food for energy,building and maintenance.

(a) Sugar is synthesized in the leaves.

(b) Hormones are synthesized in the growing parts of roots and shoots.

6. (a) Blood vessels transport the blood between heart and various organs.

(b) Blood platelets help in blood clotting thus, saving its loss.

(c) Lymph carries digested fats, fights infection, drains excessive extracellular fluid back intothe blood.

(d) Heart pumps blood with enough force into the major arteries so that it reaches every partof the body.

7. Small intestine receives bile juice from liver, which has bile salts. They emulsify them thatbreak large fat drops to fine droplets. It also receives pancreatic juice from pancreas. Lipaseenzyme from pancreas breaks down fats into fatty acids and glycerol. Thus, fats are digestedin small intestine in our body.

8. Respiration Breathing

1. It is a biochemical process. 1. It is a physical process.

2. O2 reacts with food and energy is released. 2. Only exchange of gases.

3. Energy is released. 3. No energy released.

4. It occurs in cytoplasm and mitochondria. 4. Occur in respiratory organs.

9. Aerobic respiration Anaerobic respiration

1. Presence of air required. 1. Presence of air not required.

2. Occur in two steps: 1st glycolysis in 2. Complete process occurs in cytoplasm.

cytoplasm, 2nd in mitochondria.

3. Glucose completely oxidized to CO2 3. Glucose incompletely oxidized to either

and H2O. an organic acid or alcohol with CO2.

4. Large amount of energy produced. 4. Less energy produced.

5. Examplesman, higher plants. 5. Examples yeast, lactobacillus.


10. Respiration in plants works like this:

(a) All parts of plants like roots, stem, leaves, etc. respire individually.

(b) There is little transport of gases from one part to another.

(c) Respiration occurs at much slower rate.

WORKSHEET-921. There are two conducting tissues in transport system of plants, first is xylem and second is

phloem.

(a) Water and minerals dissolved in it move up to leaves from root through tracheids andvessels which are two kinds of elements of xylem.

(b) Prepared food are transported through sieve tubes of phloem.

2. Arteries. They carry blood away from the heart (arteriole: small arterial branch). They havethick and flexible walls to endure higher pressure of blood.

Veins. They convey blood towards the heart (venule: small vessel that carries blood fromcapillaries to veins). They have thinner wall but there are valves in them at regular distance toprevent back flow of blood especially when blood is returning back to heart from lower organs.

3. Stomata

4. Pulse. Pulse is contraction and expansion of heart felt in major arteries at specific locationsin our body. We can measure it with the help of a stethoscope or just by feeling radial orcarotid artery.

5. (a) They throw away oxygen and water vapour through stomata.

(b) Some wastes like gums, oil and resins may be stored in stem, leaves and bark and shedoff from time to time.

6. Blood pressure. The pressure felt by the arterial wall due to presence of blood in it. It ismeasured by sphygmomanometer. It is more when ventricles contract, it is less whenventricles relax.

7. The graphical representation of electrical changes during heartbeat is known asElectrocardiogram (ECG). Instrument used for detection of heartbeat is Electrocardiograph.

8. It is regulated by:

(a) The amount of excess water

(b) The amount of dissolved waste in blood.

62 XS C I E N C E

9. When both the kidneys of a person stop working for some reason, in order to clean theblood of metabolic wastes and to maintain normal levels of water and mineral ions in thebody fluids, an artificial kidney is employed. The procedure used in artificial kidney inplace of normal is called dialysis.

10. CO2 and water are needed for the photosynthesis. CO2 enters the leaf through stomapresent on its surface. These pores open in day time in most of plants though in desertplants they open at night to reduce the loss of water. Water is absorbed by roots from thesoil along with other materials like nitrogen, phosphorus, iron and magnesium.

11. Nutrition in animals are heterotrophicholozoic. It has five steps:

1. Ingestiontaking in food

2. Digestionbreaking it into smaller components

3. Absorptiontaking in the digested food

4. Assimilationutilising the absorbed food to produce energy or for growth, repair andreproduction.

5. Egestionthrowing out undigested food.

WORKSHEET-93

1. (a) (ii)

(b) (i)

(c) (iv)

(d) (iii)

2. Conditions necessary for autotrophic nutritionphotosynthesis

(a) Chlorophyll

(b) Carbon dioxide

(c) Water

(d) Light

By-product are starch and oxygen.

3. Autotrophs can use simple inorganic molecules like water and carbon dioxide while complexorganic molecules are used by heterotrophic organisms such as proteins, fats andcarbohydrates.

4. Plants exchange gases through stomata. Large intercellular spaces ensure that each cell is incontact with air. Carbon dioxide and oxygen are exchanged here. They can also do itthrough their surface on stem, roots etc.

5. Auricle Ventricle

(a) Upper, thin walled chambers. (a) Lower, thick walled chambers.

(b) Receive blood from veins. (b) Receive blood from the auricles.

(c) Push blood into the ventricles. (c) Push blood into the arteries.

6. There are fine hair and mucus in the inner lining of nose which filter the incoming air ofgerms and dust. Moreover, the air attains the optimum temperature before reaching thelungs.


7. (a) Xylemminerals and water in plants.

(b) Phloemdissolved food and hormones in plants.

(c) Pulmonary veinoxygenated blood from lungs to left auricle of heart in humans.

(d) Vena cavadeoxygenated blood from all parts of the body to right auricle of the heartin human.

8. (a) (iv), (b) (iii), (c) (i), (d) (ii)

9. (a) (i), (b) (iv), (c) (ii), (d) (iii)

10. (a) Protein

(b) Starch

(c) Protein

(d) Fats

WORKSHEET-94

1. All respiratory systems have some important features:

(a) Large surface area.

(b) Thin and delicate surface for diffusion and exchange of gases. It is generally located inprotected inner part of body.

(c) Rich blood supply to respiratory organ

Since all of them are present in alveoli, hence it is perfectly designed for exchange of gases.

2. Fats are first emulsified with the help of bile salts followed by their breakdown in fatty acidsand glycerol due to the action of lipase. All these events take place in first part of smallintestineduodenum.

3. The food prepared by plant may be sucrose, amino acids or other materials. It is done withthe help of living cellssieve tubes and companion cell of phloem tissueby utilizingenergy of ATP. The movement occurs both upwards and downwards from the place offormation (leaves) to place of use (growing buds) depending upon the situation.

4. Salivary glands, liver, pancreas.

Salivary glands. There are three pairs of salivary glands. Saliva contains an enzyme salivaryamylase which converts starch to maltose.

Liver. Largest gland of body weighs 1.5 kg. It produces bile juice which is stored in gallbladder. Bile juice (1) neutralizes the acid, (2) makes food alkaline, (3) emulsify fat.

Pancreas. Second largest gland. Secrete pancreatic juice

Pancreatic juice contains trypsin to digest protein, amylase to digest polysaccharides (complexcarbohydrates) and lipase to break down fats to fatty acid and glycerol.

5. (a) The two vena cava (superior and inferior) bring deoxygenated blood to human heart.

(b) Right atrium receives this blood.

(c) When the right atrium contracts, this blood is poured into the right ventricle and whenthe right ventricle contracts, it pumps the blood into the pulmonary artery which carriesit to the lungs for oxygenation.

64 XS C I E N C E

6. Blood is liquid connective tissue. It is chiefly formed of two components:

1. Fluid matrix or plasma. Which is pale in colour and transports substance like dissolvedcarbon dioxide, glucose, amino acids, urea etc. has mainly water, some proteins likealbumin, fibrinogen (blood clotting protein) and many other substances to be transported.

2. Cellular elements are of three types:

(a) Red blood corpuscles (R.B.C.) or erythrocytes, which transport O2 and CO2. Theyare enucleated, disc shaped, full of a red coloured protein pigment, haemoglobin.

(b) White blood corpuscles (W.B.C.) or leucocytes, which fight disease-causing agent.They are larger, nucleated and are of different types.

(c) Blood platelets or thrombocytes, which help in blood clotting. They are fragments ofsome larger cells hence, do not have nucleus.

7. Nutrition in Amoeba. It occurs through phagocytosis. It captures food by pseudopodia(ingestion) ingested food, enclosed in cell membrane is called food vacuole.

WORKSHEET-951. DiagramHuman digestive system.

2. (a) Food is crushed into small pieces by the teeth.

(b) It mixes with saliva and the enzyme amylase (found in saliva) breaks down starch intosugars.

(c) Tongue helps in thorough mixing of food with saliva.


3. (a) Pulmonary vein(b) Left atrium(c) When the left atrium contracts, the oxygenated blood is poured into the left ventricle.

When the left ventricle contracts the blood is pumped into the aorta, the largest arterywhich distributes it to all the parts of the body through its finer branches or arterioles.

4. Exchange of gases in tissues:

(a) Most of oxygen is carried by haemoglobin in blood. On reaching the tissues, it getsdiffused into the cells as it is in higher concentration than in the cells.

(b) The carbon dioxide, which is formed in the cells, gets accumulated there in higherconcentration as compared to in the blood, now diffused into the blood.

(c) The CO2 mosly dissolved in blood plasma reaches the lungs, from where it is expelledduring exhalation.

5. (a) At the roots, cells in contact with the soil actively take up the ions. This creates adifference in concentration of these ions between the roots and the soil.

(b) Water, therefore, moves into the root to eliminate the difference.

(c) There is a steady movement of water through a continuous system of water conductingchannels from roots to leaves.

(d) Transpirational pull is operational mainly during day as stomata are open. Though atnight it is mainly root pressure which helps in pushing the water up. Transpiration alsohelps in cooling of plant tissues.

6. (a) Photosynthesis

(b) Autotrophs

(c) Chloroplast

(d) Guard cells

(e) Heterotrophs

(f) Pepsin

7. A circulatory system is a vascular system (i.e. with tubes or vessels) in which the transportfluid moves rhythmically in a particular direction, since it is propelled by a muscularpumping structure.

The circulatory system is divided into two parts: the cardiovascular system, which includesthe heart and blood vessels, and the lymphatic system, which consists of lymph nodes andlymph organs. Each component serves a specific purpose. For example, the cardiovascularsystem is responsible for the transportation of oxygen, hormones and waste material, whilethe lymphatic system protects the body against infections.

In the human being, many substances like nutrients, oxygen, CO2, hormones, waste productsare to be transported from one place to other. For example, materials like glucose, fatty acidsand oxygen have to be transported to each and every cell of the body where energy isrequired. Similarly, hormones are to be transported to the target organs. Also the wasteproducts like urea etc. are to be transported to kidneys where they are thrown out of the body.

The most important part of the entire circulatory system is, of course, the heart. The heart isa four-chambered double pump that pumps deoxygenated blood into the lungs that thenprovide oxygen to the entire body starting from, once again, the heart.

66 XS C I E N C E

WORKSHEET-961. Mechanism of Inhalation. The thoracic cavity expands when diaphragm and rib muscles

contract. The thorax moves upwards and outwards, increasing the volume inside thoraciccavity. The air pressure in the cavity decreases, hence the air rushes into the lungs throughnostrils, trachea and bronchi.Mechanism of Exhalation. Exchange of gases between alveolar sacs and blood occurs and airhaving CO2 enters the alveoli. The thoracic cavity comes back to its original size as diaphragmmuscles relax. Air containing CO2 is exhaled out through bronchi, trachea and nostrils.

2. (a) Anchoring the plant.(b) Source of water and minerals.(c) Availability of oxygen for respiration of root cells.(d) Symbiotic association with microbes.

3. Respiration in human beings takes place through the respiratory system which has a pair oflungs located to thorax, passages through nose, pharynx, trachea, bronchi and bronchioles.In human beings:(a) Nostrils: they are lined with fine hair and mucus to filter the air of dust and germs.(b) Pharynx [ throat]: common passage for air and food.(c) Larynx: voice box with vocal cords to produce sound. It has a loose cartilage in men

which protrudes out and is called Adams apple.(d) Trachea: windpipe, 11 cm long, guarded by 16-20 incomplete rings of cartilage which

prevent it from collapsing.(e) Bronchi: trachea divides into two bronchi at lower end. The bronchi divide into

bronchioles which enters into lungs.(f) Lungs, bronchioles and alveoli: bronchi on entering the lung, branch continuously as

bronchioles to finally terminate into balloon like thin structures called alveoli. They arerichly supplied with blood capillaries. Alveoli are the sites of gas exchange.

4. Heart is the pumping organ in our circulatory system. It has four chambers, two upper, thinwalled and small chambersatria, while lower two are larger and thick walledventricles. Theright atrium receives blood from the vena cava and pumps the blood into the right ventricle. Bloodis sent to lungs, where it is oxygenated. Then it is sent through the right and left pulmonary veinsto the left atrium where it is pumped to the left ventricle. The blood then travels to the ascendingaorta where it leaves the heart and delivers oxygen to different parts of the body.


Ventricles are thick walled as they have to generate pressure in the pumped blood. Valvesare present between atria and ventricles to prevent back flow of blood. Such a flow in whichblood enters the heart twice is called double circulation. It helps in keeping the oxygenatedand deoxygenated blood separate.

WORKSHEET-971. Heart. Heart lies in the middle of the chest cavity, between the lungs. It has four chambers,

two upper, thin walled and small chambersatria, while lower two are larger and thickwalledventricles. The right atrium receives blood from the vena cava and pumps theblood into the right ventricle. Blood is sent to lungs, where it is oxygenated. Then, it is sentthrough the right and left pulmonary veins to the left atrium where it is pumped to the leftventricle. The blood then travels to the ascending aorta where it leaves the heart anddelivers oxygen to different parts of the body.

Ventricles are thick walled as they have to generate pressure in the pumped blood. Valvesare present between atria and ventricles to prevent backflow of blood.

2.

The right atrium receives blood from the vena cava and pumps the blood into the rightventricle. Blood is sent to lungs, where it is oxygenated. Then it is sent through the rightand left pulmonary veins to the left atrium where it is pumped to the left ventricle. Theblood then travels to the ascending aorta where it leaves the heart and delivers oxygen todifferent parts of the body.

68 XS C I E N C E

Vena cava from upper and lower body → right atrium → right ventricle → pulmonaryarteries to lungs → lungs → pulmonary veins → left atrium → left ventricle → aorta →arteries to all organs of upper and lower body

Such a flow is called double circulation.3. (a) Autotrophic nutrition. Organism makes its own food (organic compounds) from simple

(inorganic) raw material i.e., plants and some bacteria.Heterotrophic nutrition. Organisms depend on other living organisms for their food i.e.,fungi, animals.Mode of heterotrophic nutrition depends upon type and availability of food.

(b)

WORKSHEET-98

1. Within the kidney are small functional units called nephrons, which are made up ofglomerulus, Bowmans capsule, proximal convoluted tubule, loop of Henles, distal convolutedtubule, and collecting duct.

Steps of urine formation

Each kidney is made of millions of nephron. Each nephron has a hollow cup likeBowmans capsule and a long tubule system following it. Arteriole branching fromrenal artery make bunches of capillaries, one of which is called a Glomerulus. The firststep in the filtration process is when the blood enters the glomerulus, where it is thenpumped through the porous walls into the Bowmans space. This filtered plasma ismainly water, various salts, urea and glucose. The glomerular filtrate then passesthrough the proximal convoluted tubule, loop of Henle, the distal convoluted tubule sothat useful substances are reabsorbed by blood present in the capillaries around them.


The liquid is concentrated and collected in collecting duct. It is now called urine and pouredin ureters to be carried to urinary bladder. Urine is passed out through urethra, when theurinary bladder is full and due to pressure there is an urge to do so. Sphincter musclesregulate this process.

Osmoregulation and excretion are intimately related, these processes together maintainhomeostasis (i.e. staying the same), and are performed by the same set of organs. Thekidney is the major organ of osmoregulation and excretion in vertebrates.

2. The kidneys (renal glands) lie high in the abdominal cavity on both sides of the vertebralcolumn. The right kidney is slightly lower than the left to make room for the liver. Eachkidney is bean shaped and the concave portion faces medially where the renal artery andvein and ureters attach. The kidney collects and transports urine from the kidney to ureters.

The kidneys regulate:

1. The volume of blood plasma (blood pressure).2. The concentration of waste products in the blood [excretion].3. The concentration of electrolytes such as Na+, K+, HCO3

_ and other ions [osmoregulation].4. The pH of plasma.

3. (a) Transpiration is the process of removal of water vapours from the aerial parts of a plant,mainly through stomata in the leaves.

(b) There are two conducting tissues of plants. First is xylem and second is phloem .Tracheids and vessels which are two kinds of elements of xylem.

(c) Tracheids are found in all vascular plants. They are spindle shaped, have only pits andare not very efficient.

(d) Vessels are found in flowering plants, are tube like, have perforation plates and pitsmaking them more efficient.

(e) When loss of water vapour occurs from leaves of plants due to transpiration, deficit ofwater is created in the leaves. Evaporation of water molecules from the cells of a leafcreates a suction force which pulls water from the xylem cells.

( f ) Water and minerals dissolved in it move up to leaves from root through tracheids andvessels, pulling water and minerals upwards through xylem elementsascent of sap.Thustranspiration helps in upward movement of water from roots to leaves.

(g) The roots of a plant absorb water and dissolve substances from the soil, which is neededby the aerial parts of the plants. As such these substances are to be transported fromroots up to stem, leaves and flowers.

70 XS C I E N C E

WORKSHEET-99

1. (b) 2. (a) 3. (b) 4. (b) 5. (a) 6. (d) 7. (c) 8. (b) 9. (b) 10. (b)

11. (a)

WORKSHEET-100

1. (c) 2. (c ) 3. (d) 4. (c) 5. (c) 6. (c) 7. (c) 8. (a) 9. (c)

WORKSHEET-101

1. (d) 2. (d ) 3. (d) 4. (b) 5. (c) 6. (b) 7. (c) 8. (c)

WORKSHEET-102

1. (d) 2. (b ) 3. (b) 4. (b) 5. (b) 6. (c) 7. (d) 8. (b) 9. (c)

WORKSHEET-103

1. (a) 2. (d) 3. (d) 4. (d) 5. (c) 6. (d)

WORKSHEET-104

1. (b) 2. (c ) 3. (b) 4. (d) 5. (d) 6. (c)

WORKSHEET-105

1. (d) 2. (d ) 3. (c) 4. (a) 5. (b) 6. (a) 7. (d)

WORKSHEET-106

1. (d) 2. (c ) 3. (a) 4. (a) 5. (c) 6. (d) 7. (b) 8. (c)

WORKSHEET-107

1. (a) 2. (d ) 3. (b) 4. (a) 5. (d) 6. (d) 7. (a) 8. (d) 9. (b)

1. (d)

2. (a)

3. The swelling of paired kidney-shaped cells [called guard cells] due to absorption of watercauses opening of stomatal pores while shrinking of guard cells closes the pores.

4. Gastric glands in stomach release hydrochloric acid, enzyme pepsin and mucus. Mucusprotects the inner lining of stomach from the action of hydrochloric acid and enzyme pepsin.

5. Autotroph Heterotroph

! They prepare their own food [complex ! They depend on other organism for their

organic matter] from inorganic raw material. food.

! They are also termed as producers in a food ! They are consumers, parasites or

chain. decomposers.

e.g., green plants. e.g., human being, cuscuta, mushroom.


6. No,this plant will not remain healthy for a long time because:

(a) It will not get oxygen for respiration.(b) It will not get carbon dioxide for photosynthesis.(c) Upward movement of water and minerals would be hampered due to lack of transpiration.

7. (a) Photosynthesis(b) Nitrogen(c) Chloroplast.

8. Nephron

9. (a) Artery Vein

1. Have thick, elastic and muscular 1. Have thin, non-elastic and walls.

walls.

2. Lumen is narrow. 2. Lumen is wide.

3. Carry blood from heart to all body 3. Carry blood from all body parts to heart.parts.

4. Carry oxygenated blood (except 4. Carry oxygenated blood (except

pulmonary artery). pulmonary vein).

(b) The blood circulation in human heart is called double circulation because the blood passesthrough the heart twice in one complete cycle of the bodyonce through the right half inthe form of deoxygenated blood and once through the left half in the form of oxygenatedblood.

(c) In four chambered heart, left half is completely separated from right half by septa. Thisprevents oxygenated and deoxygenated blood from mixing. This allows a highly efficientsupply of oxygenated blood to all parts of the body. This is useful in animals that havehigh energy needs, such as birds and mammals.

72 XS C I E N C E

WORKSHEET-113

1. (d) All of these

2. (d) All of these

3. (b) Synapse

4. (d) All of these

5. (d) All of these

6. (b) Receiving instructions from all parts of body and integrating it.

7. (b) Peripheral nervous system

8. (a) Cranium

9. (d) Cytokinin

10. (c) Cells shrinking and swelling due to electrochemical signal to change in amount of water.

11. (d) 12. (a)

13. (c) 14. (d)

15. (b) 16. (d)

WORKSHEET-1141. (c) 2. (b ) 3. (d) 4. (c) 5. (c) 6. (d) 7. (b) 8. (b) 9. (a) 10. (c)

11. (b) 12. (a) 13. (b)

WORKSHEET-1151. (c) 2. (c ) 3. (b) 4. (d) 5. (a) 6. (b) 7. (c) 8. (d) 9. (b) 10. (c)

WORKSHEET-116

1. Nervous system and endocrine system.

2. Pons.

3. Nervous tissue and endocrine (glandular) tissue.

4. Pituitary secretes growth hormone, which controls the growth of bones and muscles increasingheight during childhood.

5. The type of movement which shows growth at the point of receiving stimulus. For example,shoot growing towards light.

6. Gibberellins.

7. Testosterone and oestrogen in males and females respectively.

8. Hypothalamus and pituitary gland.

9. Nerve cell or neuron.

10. Thyroxine regulates the metabolism of carbohydrates, fats and proteins.

8 CONTROL AND COORDINATION

73C O N T R O L A N D C O O R D I N A T I O N

11. Chemotropism is growth of a plant part towards or away from a chemical stimulus.12. Pancreas. Trypsin.13. Thyroid secreting thyroxine. It is located in the neck region.14. Non-directional growth, for example, folding and drooping of leaves of touch-me-not plant.15. All information from the environment is detected by specialized tips of some nerve cells.

They are receptors located in our sense organs.16. Movement on the touch-sensitive plant.17. Insulin and glucagon.

Insulin lowers the level of blood sugar. Glucagon raises the level of blood sugar.

18. (a) Voluntary action Involuntary action

1. It involves conscious thinking by the 1. It is the action in response to somebrain, e.g., walking. change in the environment without

thinking about it, e.g., reflex action.

2. Voluntary actions are controlled by 2. Involuntary actions are controlled byour forebrain. our spinal cord, midbrain and hind-

brain through peripheral nervoussystem, e.g., peristalsis.

(b) Involuntary actions are beating of heart, salivation in the mouth on viewing a tasty food.

WORKSHEET-1171. Phototropism is directional movement of plant part towards or away from light, e.g., shoot

grows towards light. Geotropism is movement of plant parts in response to gravitationalpull, e.g., growth of roots downwards while shoot grows away from gravity.

2. Receptors are specialized tips of some nerve cells located usually in our sense organs. Thereceptors for taste are gustatory receptors while those detecting smell are olfactory receptors.

3. Plant movements dependent on growth are directional that is point of movement is same aspoint of receiving stimulus. For example, roots of a seedling grow along gravity while itsstem grows towards sunlight.Plant movements independent of growth are non directional that is point of movement isnot the same as point of receiving stimulus. For example, folding up and drooping of leavesof touch-me-not plant.

4. (a) Auxin (b) Gibberellin(c) Cytokinin (d) Abscisic acid

5. (a) Pineal gland (b) Pituitary gland(c) Thyroid (d) Thymus

6. (a) (iii), (b) (iv), (c) (i), (d) (ii)7. Growth hormone is responsible for growth of muscles and bones. If level of growth hormone

during childhood is low, height may not increase causing dwarfism. If opposite happens,height will increase abnormally causing gigantism.

8. Reflex action. It is a sudden and involuntary action in response to change in the environment,e.g., withdrawing hand from a hot object. These actions occur without thinking about them.Reflex arc. The pathway of quick transmission of nerve impulse in a reflex action is calledreflex arc. It is a connection between input nerve (sensory nerve) and the output nerve(motor nerve) and it is formed in the spinal cord as shown below:

74 XS C I E N C E

Stimulus → Receptor organ → Sensory nerve →Spinal cord → Motor nerve → Effector organ → Action

9. Three major regions of human brain are:(a) Forebrain which includes celebral hemispheres (cerebrum).(b) Midbrain.(c) Hindbrain which includes pons, cerebellum and medulla.Cerebellum.

10. A living organism has to respond to changes in its surroundings to (a) protect itself (b) gainadvantage from present situation.Systems of control and coordination help an organism to respond properly to these situations.

11. (a) Oestrogen (b) Growth hormone(c) Insulin (d) Thyroxine

12. (a) Pituitary (b) Pancreas (c) Adrenal (d) Testes

WORKSHEET-1181. Chemical coordination in animals occurs through chemicals called hormones which are

secreted by endocrine glands. Endocrine glands are ductless glands which pour their secretionsdirectly into the blood which transports them to the target organs or tissue where actionoccurs, e.g., during an emergency situation like frightening/overexcitement, adrenaline, ahormone is secreted by the adrenal gland into the blood which transports it to target organsincluding heart. As a result, the heart beats faster resulting in supply of more oxygen to ourmuscles. Breathing rate also increases due to faster contraction of diaphragm and rib muscles.All these responses together enable the animal body to deal with the situation.

2. Chemical coordination occurs in plants with the help of plant hormones. They are synthesizedat places away from point of action and simply diffuse in the area of action. Thus, they helpin coordinating growth, development responses to the environment.

3. Secretion of oestrogen from ovaries stimulates development of secondary sexual characteristicsat puberty (10-12 years) in females.Secretion of hormone testosterone from testis stimulates secondary sexual characteristicsduring puberty (13-14 years) in males.Feedback mechanism. It regulates timing and amount of hormone to be released in thebody, e.g., rise in sugar level in the blood is detected by pancreas, hence insulin secretion isincreased. But when sugar level falls, its secretion decreases.


4. (a)

(b) Labels to be indicated on above diagram are cerebrum and cerebellum.

(c) Cerebellum controls posture, balance of body and accurate voluntary movements.

WORKSHEET-119

1. (a) (i) Phototropism. Growth dependent movement in which a part of plant moves towardor away from direction of light stimulus. For example, shoot is positively phototropicand roots are negatively phototropic.

(ii) Geotropism. Growth dependent movement in which a part of plant moves towards oraway from direction of gravitational pull. For example, roots are positively geotropicand shoot is negatively geotropic.

! Fill a conical flask with water.

! Cover the neck of the flask with a wire mesh.

! Keep two or three freshly germinated bean seeds on the wire mesh.

! Take a cardboard box which is open from one side.

! Keep the flask in the box in such a manner that the open side of the box faces lightcoming from a window.

76 XS C I E N C E

! After two or three days, you will notice that the shoots bend towards light and rootsaway from light.

! Now turn the flask so that the shoots are away from light and the roots towards light.Leave it undisturbed in this condition for a few days.

(b) (i) Auxin. This hormone is responsible for elongation. It causes bending of shoot towardslight and twining of tendrils around a support.

(ii) Abscisic acid. It inhibits growth of plant parts to save them during unfavourableconditions. For example wilting and falling of leaves, flowers.

2. Information from the environment is detected by dendritic tip of a neuron located in the senseorgan. A chemical reaction sets off here and it creates an electrical impulse which travels fromdendrite to cell body and then along the axon to its endings where it sets off the release of somechemicals. The chemicals cross the synapse and set off a similar electrical impulse in dendritesof next neuron. Another synapse at the end of its axon delivers the impulse to the other cellslike muscle cells/glands (effector organs) which react to perform the action.

OR

(a)

(b) (i) Dendrite(ii) Axon

WORKSHEET-120

1. Feedback mechanism is a way of controlling the wastage. It controls timing and amount ofhormone produced. For example, production of hormones. It regulates timing and amountof hormone to be released in the body, e.g., rise in sugar in the blood is detected by pancreas,hence, insulin secretion is increased. But when sugar falls, its secretion decreases.

2. Synapse. A gap junction point between nerve endings of one neuron and dendrites ofanother neuron.Transmission of information impluse:(a) The information is acquired at the end of the dendrites tip of the neuron.(b) A chemical reaction is set off which creates an electrical impulse.(c) The electrical impulse travels from the dendrites to the cell body and then along the

axon to its end.(d) At the axon endings, the electrical impulse sets off release of some chemicals which cross

the synapse and start a similar electrical impulse in the dendrites of next neuron.At neuromuscular junction, similar events occur in order to transmit the information.


3. Brain and spinal cord constitutes the central and peripheral nervous systems. Brain box andvertebral column protect the components of central nervous system.

4. Some plants like pea plants climb up other plants and fences by means of their tendrils.These tendrils are sensitive to touch. When they come in contact with any such support,auxins are produced by root tip and shoot tip and diffuse to part of the plant away fromsupport and cause the cells to grow longer, the part of the tendril in contact with the supportgrow causing the tendril to circle the object of support and cling to it.

1. (b). 2. (a).

3. When an electrical signal reaches the end of axon of one neuron, it releases certain chemicalsubstances that cross the synapse and move towards the dendrite of next neuron generatinganother electrical signal.

4. (a) Adrenal (b) Pancreas (c) Pituitary (d) Ovaries.

5. (a) Auxin (b) Gibberellin (c) Cytokinin (d) Abscisic acid.

6. Electrochemical messages called nerve impulses transfer the information from receptorspresent in various organs or from sense organs of CNS through nerves.

The orders from CNS are conveyed via nerves to the muscles or glands (effectors). Glandsproduce secretion (like hormones) which, in turn, control many metabolic activities.

7. Reflex arc

(a) Sensory neuron (b) Spinal cord (CNS)

(c) Motor neuron (d) Effector = Muscle in arm.

8. Central nervous systemBrain and spinal cord

Peripheral nervous systemcranial, spinal and visceral nerves

The components of central nervous system protected brain box ,vertebral column andfluid filled balloon like structure formed from meninges and cerebrospinal fluid.

9. (a) Oestrogen. It regulates production of ova from ovaries, secondary sexual characters infemales and health of reproductive organs.

(b) Insulin. It regulates blood sugar by lowering its level.

(c) Adrenaline. It increases heart rate and supply of blood to various organs and helps thebody to cope with emergency situations.

(d) Growth hormone. It regulates growth and development of bones and muscles.

(e) Testosterone. It controls the changes of body features associated with puberty in male.

SOLUTIONS TO

PRACTICE PAPERS

79P R A C T I C E P A P E R S

1. Veins.

2. D.C. has constant magnitude and same direction. A.C. vary in magnitude and direction.

3. Since, resistance (R), = VI

∴ R1 > R2 > R3

Hence, R1 is maximum and R3 is minimum.

4. The oxidation of oil and fats present in food materials to form products that have bad odourand taste is called rancidity.

5. All three metals are highly reactive. They react vigorously with oxygen and water to evolvehydrogen gas. The reaction is highly violent and exothermic, so the evolved gas catches fireeasily. Thus, to prevent its reactivity with oxygen and water, it is stored under oil.

6. Thyroxine, an iodine containing hormone which regulate metabolism of carbohydrates,proteins and fats thereby regulating growth.

Due to deficiency of iodine in our food, i.e., deficiency of thyroxine, goitre-swelling of neckdue to enlargement of thyroid gland occurs.

7. Some of the criteria for selecting a good fuel are:


(b) low cost;


(d) a high calorific value;


(f) no combustion products that are poisonous or environmental pollutants.

8. The purpose behind the use of reflector in solar devices is to focus the sunrays to achievehigher temperatures.

9. It is in the form of co-centric circles on the plane of the paper.

10. Tungsten is preferred because;

(a) It has high resistance and high melting point.

(b) It glows on heating.

11. When ferrous sulphate crystals are heated, following observations are made:

(a) The colour of crystals changes from green to reddish brown due to formation of iron (III)oxide.

(b) Pungent smelling gases sulphur dioxide and sulphur trioxide are evolved.

12. (a) Copper, corrosion

(b) Basic copper carbonate.

PRACTICE PAPER-I

80 XS C I E N C E

13. (a) Substance getting oxidised H2 to H2O

Substance getting reduced CuO to Cu

(b) Substance getting oxidised Na to Na+

Substance getting reduced O2 to O2

14. On eating spicy food, excess of dilute hydrochloric acid is produced in our stomach. Thisexcess acid produced leads to burning sensation. This can be neutralised by taking antacidswhich are mild bases like magnesium hydroxide.

15. Phototropism. It is tropic movement in the direction of light or away from it, e.g., shootsbend towards light while roots grow away from it. Hence, shoots are positively phototropicand root is negatively phototropic.

Geotropism. Roots grow downward the earth, hence they are positively geotropic whereasstem grows upward, away from earth, hence it is negatively geotropic.

Abscisic acid.

16. Receptors are special nerve cells in animals, which can perceive certain stimuli. For example,photoreceptors perceive light, whereas phonoreceptors perceive sound.Cerebellum helps in maintaining balance and posture of body.

17.

18. It is a process of providing an alternative path to excessive charge that may sometimes leakof the body of a high voltage metallic appliance. The colour of earth wire is green. One endof this wire is connected to the appliance and the other is earthed. Earth is always at zeropotential, therefore, any extra charge successfully reaches earth without affecting appliancesthus, preventing shocks.

19. (a) To find effective resistance, first we find resultant of series combination Rs = 1 + 1 = 2 ΩNow, 2 Ω and 2 Ω are in series, so their effective resistance will be

pR1 1 1

2 2= +

∴ Rp = 1 Ω

(b) ä I =p

VR

∴ I = 41

= 4 A.


(c) V1 = I Rp

= 4 × 1 = 4 volts.

20. ! Fix a sheet of white paper on a drawing board using some adhesive material.

! Place a bar magnet in the centre of it.

! Sprinkle some iron filings uniformly around the bar magnet. A salt-sprinkler may beused for this purpose.

! Now, tap the board gently.

21. (a) By heating alone, e.g.

2HgS + 3O2 ∆→ 2HgO + 2SO2

(Cinnabar) 2HgO ∆→ 2Hg + O2

(b) By using coke as reducing agent. Sometimes, reactive metals such as Na, Mg and Al canalso be used, e.g., ZnO + C → Zn + CO

(c) Oxides of highly reactive metals are subjected to process of electrolytic reduction.

NaCl (Molten) → Na+ + Cl

Reaction at cathode

Na+ + e → Na

At anode Cl e → Cl

Cl + Cl → Cl222. (a) Hydrogen gas.

(b) Bring a burning splinter near the mouth of the test tube containing hydrogen gas. It burnswith a pop sound and the burning splinter extinguishes.

(c) It is lighter than air.

(d) The above gas is collected by downward displacement of water, as it is insoluble in water.

82 XS C I E N C E

23.

In this method, the impure copper metal forms the anode and a thin strip of pure metalforms the cathode. A solution of the metal salt, i.e., copper sulphate is used as an electrolyte.On passing electric current through the electrolyte, Cu2+ ions from the anode dissolves intothe electrolyte and an equivalent amount of Cu from the electrolyte is deposited on the cathode.

Reaction at cathode: Cu2+ + 2e → Cu

Reaction at anode: Cu → Cu2+ + 2e (Oxidation)

24. (a) Magnetic field. It is the region around a magnet within which another magnet or amagnetic substance experiences force of attraction due to it.

Direction of magnetic field lines can be determined by:

(i) using a compass, where needle points.

(ii) by drawing tangent to field lines at that point.

(b) Right hand thumb rule. If we stretch thumb of right hand and fold the fingers, thenthumb indicates the direction of current and folded fingers indicate the direction ofinduced magnetic field.

25. (a) The two vital functions of kidneys are:

! Excretion of nitrogenous wastes.

! Osmoregulation regulation of water and salt content in blood.


(b) Diagram of urinary system of human being.

26. (a) Double decomposition reaction.

(b) Oxidation reaction.

(c) Decomposition reaction.

(d) Single displacement reaction

(e) Combination reaction.

27. (c) 28. (d) 29. (a) 30. (a) 31. (a) 32. (c)

33. (a) 34. (c) 35. (a) 36. (a) 37. (d) 38. (b)

39. (d) 40. (a) 41. (d)

""

84 XS C I E N C E

PRACTICE PAPER-II

1. Nastic movements.

2. SI unit for resistance is ohms, Ω.

SI unit for resistivity is ohm-metre, Ω m.

3. 1 volt = 1 joule/1 coulomb.

Potential or potential difference.

4. Substance getting oxidised HCl to Cl2Substance getting reduced MnO2 to MnCl2

5. An amalgam is an alloy in which one of the metals is mercury.

6. Transpiration is the process of removal of water vapours from the aerial parts of a plant,mainly through stomata in the leaves.

Evaporation of water molecules from the cells of a leaf creates a suction force which pullswater from the xylem cells. This transpiration helps in upward movement of water fromroots to leaves.

7. 2 1

1

R R100

R −

× =

1A

2 1

1100

l ll

−×

∴ % increase = 25%

Resistivity is a constant, therefore, it will not increase.

8. Electric motor has split rings whereas electric generator has slip ring commutator. Electricmotor converts electrical energy to mechanical energy whereas electric generator convertsmechanical energy to electrical energy.

9. I would use renewable and pollution free sources of energy to heat my food. Because, it wouldnot disturb the ecological balance as well as it would be reproduced in nature by cyclic processwhen it would be used once.


11. When lead nitrate crystals are heated, following observations are made:

(a) The colour of crystals changes from white to yellow due to formation of lead oxide.

(b) Reddish brown fumes of nitrogen dioxide are evolved.

(c) Crackling sound is heard.

12. (a) 3Fe + 4H2O → Fe3O4 + 4H2↑

(b) Na2O + H2O → 2NaOH


13. (a) On heating gypsum at 373 K, it loses its water molecules and gets converted into plasterof Paris.

CaSO4 . 2H2O 373K∆→ CaSO4 . 1

2 H2O + 121 H2O

(b) On mixing plaster of Paris with water, it changes into gypsum again.

14. (a) The substance 'X' is calcium oxide and its chemical formula is CaO.

(b) When calcium oxide is mixed with water, a highly vigorous and exothermic reactiontakes place, it forms slaked lime.

CaO + H2O → Ca(OH)2

Quick- slakedlime lime

15. The main events occurring in the small intestine are as follows:

(a) Bile emulsifies fat present in the food ( emulsification means breaking of fat moleculesinto smaller globules).

(b) Pancreatic juice containing trypsin for digesting proteins and pancreatic amylase forstarch act upon the food.

(c) Bicarbonate ions secreted by duodenal wall make the medium alkaline because it isrequired for the action of pancreatic enzymes.

(d) Enzymes produced in intestinal juice complete the digestive process.

(e) Digested food, amino acids and sugar are absorbed by the blood capillaries present inthe villi of intestine.

(f) Digested fats are absorbed by lymph vessels present in the villi of intestine.

16. (a) The role of mucus is to protect the stomach lining from the action of acid and pepsin.

(b) The two vital functions of human kidneys are:

(i) Excretion. Removal of toxic wastes like urea and uric acid.

(ii) Osmoregulation. It is the process of maintaining the right amount of water andproper ionic balance in body. It is done by controlling the amount of water and saltsreabsorbed by nephron tubules.

17. Fuse is a safety device made up of a high resistance with low melting point, which works onprinciple of heating effect of electric current. No, because a fuse will not work effectively ifused this way. Commonly used is alloys of copper and tin.

18. (a) The galvanometer shows a deflection.

(b) The galvanometer shows deflection in other direction.

(c) No deflection in galvanometer.

19. (a) Key open, then R = 12 Ω, V = 6 V ∴ I = VR

= 0.5 A.

(b) Key closed, then R = 6 Ω, V = 6 V ∴ I = VR

= 1 A.

86 XS C I E N C E

20. (a) A transformer works on the principle, the varying magnetic field induces emf andvarying electric field induces magnetic behaviour.

(b) Whenever magnetic field associated with a conductor, changes an emf is induced in it.

(c) D. C. has constant magnitude and same direction whereas A.C. varies in magnitude anddirection.

21. (a) Metal sulphides and carbonates are converted into metal oxide prior to reduction becauseit is easier to extract metal from its oxide form than from any other form of the ore.

(b) Ionic compounds consist of positive and negative ions which are held together stronglydue to strong force of attraction between the oppositely charged ions. Thus, large amountof heat energy is required to overcome interionic interaction raising its melting point.

(c) Carbon cannot be used to reduce the oxides of highly reactive metals, as highly reactivemetal oxides are highly stable and have more affinity for oxygen than carbon. Thus,carbon cannot reduce them.

22. On conversion of milk into curd, its pH will decrease and will become less than 6. The pHdecreases as curd is more acidic than milk due to the presence of lactic acid. More acidic isthe substance, lesser is its pH.

23.

Materials Required. Two test tubes, test tube stands, copper sulphate solution, iron sulphatesolution.

Procedure. Take two test tubes. In one of the test tubes, take about 15 ml of copper sulphatesolution and in the another test tube, take about 15 ml of iron sulphate solution. Immerse aclean copper coin in iron sulphate solution and an iron nail in copper sulphate solution andwait for few minutes.

Observation. After few minutes, we will observe that the colour of copper sulphate solutionchanges from blue to green, while no change takes place in iron sulphate solution.

Conclusion. Iron is more reactive than copper as it displaces copper from its salt solution.

Chemical equation: Fe + CuSO4 → FeSO4 + Cu

Cu + FeSO4 → No reaction.


24. (a) Diagram of a neuron

(b) (i) Cerebrum is responsible for intelligence and memory.

(ii) Adjustment of movement of posture is controlled by cerebellum.

(c) Diabetes.

Diabetes is caused by rise in sugar concentration in the blood due to deficiency of insulinwhich lowers the blood sugar level.

25. (a)

(b) Both copper and aluminium wires are good conductor of electricity and heat because ofits metallic characters. Both have also high resistivity. Due to which, they are used forelectricity transmission.

88 XS C I E N C E

26. (a) The substance 'X' is sodium chloride (NaCl)

(b) The process is called chlor-alkali.

(c) Chlorine is liberated at anode.

(d) Sodium hydroxide is used in soap industry.

Chlorine is used as a bleaching agent. Hydrogen is used in the manufacture of ammoniagas.

27. (b) 28. (c) 29. (d) 30. (b) 31. (b) 32. (c)

33. (d) 34. (c) 35. (d) 36. (c) 37. (b) 38. (b)

39. (b) 40. (d) 41. (c)

""


PRACTICE PAPER-III

1. The mechanism by which organisms obtain oxygen from the environment and release carbondioxide is called breathing.

2. Under physical conditions of temperature and pressure remaining constant, the electriccurrent flowing through a wire is directly proportional to applied potential difference, i.e.,I ∝ V.

3. Magnetic field intensity is directly proportional to current and inversely to radius. So,double with current and twice when radius is halved.

4. Metals which displace hydrogen from dilute acids are: calcium, magnesium.

Metals which do not displace hydrogen from dilute acids are: copper, silver.5. (a) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O.

6. They can throw gases and excess water through stomata through diffusion. They can storewastes like gums and resins in old xylem tissue[wood].

7. (a) Silver is a better conductor. (b) Silver.

8. Alloys are preferred because;

(a) In alloys, resistance does not vary much with increase of temperature.

(b) They do not get oxidised on heating.9.

10. Coal and oil are the fuels used to produce heat energy to convert water to steam which, inturn, rotates (mechanical energy) the turbines in power plant. Transmission of electricity ismore efficient than transporting of coal and petroleum over the same distance. Being nearthem, expense of transport can be reduced.

11. When dilute sulphuric acid is poured on zinc granules, bubbles of hydrogen gas are evolvedfrom the surface of zinc metal and the reaction mixture becomes hot.

Zn + H2SO4 (aq) → ZnSO4 + H2↑

90 XS C I E N C E

12. The black colour of copper oxide changes to bluish-green because copper oxide reacts withdilute hydrochloric acid to form copper (II) chloride which is bluish-green.A neutralisation reaction takes place between copper oxide and dilute hydrochloric acid.

CuO + 2HCI → CuCl2 + H2O13. Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal.

Fe + H2SO4(aq) → FeSO4 (aq) + H2↑


(b) 2FeSO4(s) heat→ Fe2O3(s) + SO2(g) + SO3(g)

Ferrous sulphate Ferric oxide Sulphur Sulphur dioxide trioxide

15. (a) Central nervous system in humans consists of:

(i) Brain (ii) Spinal cord

Brain is broadly divided into three regions named forebrain, midbrain and hindbrain.

(i) Forebrain. It includes cerebrum and olfactory lobes. Cerebrum consists of sensory areascalled occipital lobe, temporal lobe, parietal lobe and frontal lobe.

Midbrain. It plays some role in involuntary action.

Hindbrain. It consists of cerebellum, pons and medulla oblongata.

(ii) Spinal cord. Cylindrical structure, beginning form medulla oblongata and extendingdownwards, lying inside the backbone.

(b) Functions of cerebrum are:

# Responsible for visual reception

# Controls muscular activity

# Controls auditory reception.

Responsible for touch, smell and regulates body temperature.

16. Reflex action. It is an unconscious and involuntary response of effectors (muscles andglands) to stimulus. In reflex action, a message from receptors is relayed by sensory nervesto the spinal cord, which sends information for response via motor nerves to effectors. Thepathway is called reflex arc.

Flow Diagram of It: Stimulus → receptor → sensory nerve → spinal chord → motor nerve→ affector → action

17.


18. (a) The strength of magnetic field increases.

(b) The strength of magnetic field increases.

(c) The polarity or direction of field lines reverses.

19. (a) Total resistance will be 4 times its original, i.e., 4 Ω.

(b) It will be 2.5 Ω.

(c) Since R ∝ lA

∴ Resultant (R) = l 64 4

= = 1.5 Ω.

20. (a) P = VI = 2.5 × 750 × 103 = 1875 × 103 = 1.875 watt

(b) R = V/I = 2.5/750 × 103 = 3.33 Ω(c) E = P × t = 1.875 × 4 = 7.5 Wh = 7.5 × 103 kWh.

21. (c) 3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4↓ (Double displacement)

(d) 2K + 2H2O → 2KOH + H2 (Displacement reaction)

22. (a) 'X' is sodium hydrogencarbonate and its chemical formula is NaHCO3.

(b) 2NaCl + 2H2O + 2CO2 → 2NaHCO3 + 2HCl

(c) When this compound is heated strongly, it decomposes forming sodium carbonate, waterand carbon dioxide.

2NaHCO3 Heat→ Na2CO3 + H2O + CO2

23. (a) Plaster of Paris (CaSO4. 12

H2O) has a strong tendency to absorb moisture and gets

converted into gypsum (CaSO4.2H2O) which sets into a hard mass. Thus, to prevent itscontact with moisture, it is stored in moisture proof container.

(b) Distilled water is pure water which does not contain any dissolved salts or gases.Rainwater contains dissolved gases like CO2 and SO2 which, in turn, produce acidslike carbonic acid (H2CO3), sulphurous acid (H2SO3) and dissociate into ions.Formation of ions in rain is responsible for the conduction of electricity in rainwaterwhile due to absence of ions in distilled water, it does not conduct electricity.

(c) Antacids are mild non-corrosive bases which are used to neutralise the excess acidity in thestomach, e.g., sodium hydrogencarbonate (NaHCO3) and milk of magnesia [Mg(OH)2].

24. (a) (i) salivary amylase. It is an enzyme present in the saliva, secreted by salivary glands.It digests starch into maltose thereby starting the digestion of carbohydrate in thebuccal cavity.

(ii) Villi. They increase the surface area for absorption of digested food into the blood.

(iii) Pepsin. It is a digestive enzyme secreted by gastric glands. It is responsible for thedigestion of proteins in stomach .

92 XS C I E N C E

(b) When the left atrium contracts, the oxygenated blood is poured into the left ventricle.When the left ventricle contracts, the blood is pumped into the aorta and the largestartery which distributes it to all the parts of the body through arteries.

25. (a) Formula used V = IRRCE = 2 + 4 = 6 Ω

(b) I = VR

; R = 3 Ω; V = 3 V ∴ I = 1 A

(c) IAB = AB

AB

VR

= 36

= 12

A

ICE = CE

CE

VR

= 36

= 12

A

(d) P.D2Ω = 12

× 2 = 1 V

P4Ω = 12

× 4 = 2 V

26. (a) When a piece of magnesium is dropped into test tube containing dil. HCl, the reactionwould be most vigorous, as it is the most reactive of the three metals.

(b) Mg + 2HCl (dil.) → MgCl2 (aq) + H2 (g)

Zn + 2HCl (dil.) → ZnCl2 (aq) + H2 (g)

Fe + 2HCl (dil.) → FeCl2 (aq) + H2 (g)

(c) Mg > Zn > Fe.

27. (d) 28. (d) 29. (a) 30. (d) 31. (d) 32. (d)

33. (b) 34. (b) 35. (c) 36. (c) 37. (c) 38. (c)

39. (b) 40. (c) 41. (b)""


PRACTICE PAPER-IV

1. Auxin and cytokinins.2. Heat energy = I2 Rt

= (5)2 × (20) × 30 = 25 × 20 × 30 = 15000 J.3. Whenever magnetic field associated with a conductor changes, an emf is induced in it.4. Oil and fat containing food items are generally flushed with nitrogen to prevent the oxidation

of oil and fats. Nitrogen being an inert gas does not react with oils and fats, prevents theoxidation of oils and fats and thus, they last longer without turning rancid.

5. Magnesium and manganese.6. Human heart is four chambered. The two upper chambers are called atria which receive

blood from large veins while the two lower chambers are called ventricles. Between leftatrium and left ventricle as well as between right atrium and right ventricle, valve arepresent which allow blood to flow only from atrium to ventricle.

7. Energy = Power × TimeTV set = ETV = 250 watt × 1 hr = 250 Wh = 0.25 kWh.

Toaster = Etoaster = 1200 watt × 1060

hr = 200 Wh = 0.20 kWh.

∴ ETV > Etoaster

8. (a) Wind energy. It can be established only in those areas where wind blows at a higher speedthan 15 km/hour to maintain the required speed of the turbine.

(b) Tides. The locations where dams to harness this energy can be built are limited.9. (a) CNG is non-renewable while hydrogen is renewable fuel.

(b) Hydrogen on burning produces only water vapours while CNG on burning producesgreenhouse gases which may lead to global warming hence, hydrogen is a cleaner fuelthan CNG.

10. R = ρ × lA

ρ =RA

l = 10 ×

− −× × ××

3 30.1 10 0.1 10227 1

= 3.14 × 107 Ω m.11. (a) Calamine (ZnCO3)

(b) (i) Concentration of ore(ii) Calcination. To convert carbonate ore to oxide form by heating it in the absence of

oxygen.ZnCO3 → ZnO + CO2

(iii) Coke using as reducing agent. Conversion of oxide ore into oxide form.ZnO + C → Zn + CO

(iv) Refining of metal.

94 XS C I E N C E

12. (a) Magnesium being a reactive metal combines with oxygen of air to form a layer ofmagnesium oxide on its surface which slows down the process of combustion. Hence, itshould be cleaned with a sand paper before burning to remove the oxide layer formedon its surface.

(b) The reaction which involves the formation of an insoluble substance is called precipitationreaction. A precipitate is generally obtained when aqueous solutions of two substancesare mixed together, e.g., mixing of aqueous solutions of sodium chloride and silvernitrate forms an insoluble precipitate of silver chloride.


CuO + 2HCI → CuCl2 + H2O

13. (a) 3H2 + N2 → 2NH3 (Combination reaction)

(b) 2H2S + 3O2 → 2H2O + 2SO2 (Redox reaction)

14. (a) Silver bromide

(b) 2AgBr Sunlight→ 2Ag(s) + Br2(g)

(c) Photochemical decomposition reaction.

15. No, the plant will not stay healthy for a long time. The reasons are:

(a) It will not be able to exchange O2 and CO2, hence respiration will be affected adversely.

(b) Photosynthesis will also be affected as CO2 will not be available.

(c) Transpiration will not take place hence, there will be no ascent of sap, and no waterabsorption from the soil.

16.

17. F = BIL, where B = Magnetic field, I = Current and L = Distance.

Force is maximum when magnetic field is perpendicular to the plane of coil.

18.


19. It is 220 V A.C. with 50 Hz frequency. 50 Hz specify frequency of alternating current.Household circuits have parallel arrangement because if something goes wrong with oneappliance, other should not be effective. Also in parallel arrangement, all appliances getsame voltage input.

20. Fractional distillation.

Products obtained which can be used as fuels are paraffin wax, fuel oil, petrol, kerosene,diesel and natural gas.

21. (a) This is because zinc is more reactive than copper and thus, will displace it from its saltsolution.

(b) This occurs due to phenomenon of corrosion. Silver metal reacts with sulphur compoundspresent in air to form silver sulphide which is black.

(c) A metal sulphide is converted to oxide form, as it is easy to extract metal from its oxideform than any other form of the ore.

22. (a) Sodium carbonate and its chemical formula is Na2CO3. 10H2O

(b) Ten molecules.

(c) 2NaCl (aq) + H2O(1) + CO2 (g) → Na2CO3 (s) + 2HCl(dil.)

23. (a) 3Fe + 4H2O ∆→ Fe3O4 + 4H2

(Red hot) (Steam)

(b) Al2O3 + 2NaOH → 2NaAlO2 + H2O

(c) K2O + H2O → 2KOH

24. Given,ll1

2=

12

ll1

2

Where = length of first wire = length of second wire

⇒ l2 = 2l1

Similarly,dd

1

2

= 23

dd

1

2

= diameter of first wire = diameter of second wire

⇒ d2 = d132

As we know,

ρ = RA

l=

R dl

2

4π

ä V1 = IR

∴ V1 = I l

d1

21

× 4 × ρπ ×

.......................... (i)

Similarly, V2 = I l

d2

22

× 4 × ρπ ×

........................ (ii)

96 XS C I E N C E

Now, putting the values of l2 and d2 in equation (ii), we get

= I l

d1

21

× 4 × 2 × 9

4

ρ

π ×

= I l

d12

1

× 32 × × 9

ρπ

............................. (iii)

Now, from equations (i) and (iii), we getVV

1

2=

I ld1

21

× 4 × ρπ ×

× dI l

21

1

9 × 32 × ×

πρ

= 9 : 8.

25. The plants show two different types of movements. They are:

Tropic movements. Movements depend on growth. They are directional movements inwhich growth is involved, are either towards the stimulus or away from it, e.g., when seedgerminates, root grows downwards and stem grows upwards.

Nastic movements. They are non-directional movements, i.e, neither towards nor away fromthe stimulus in which no growth is involved, e.g., folding up and drooping of leaves oftouch-me-not plant (sensitive plant) on touching.

Human brain. Brain is protected inside a bony box or skull. Further, it is also protected bya shock absorbing fluid-filled balloon made of three membranes (meninges). It has threemajor parts. These are:

(a) Forebrain. It is the main thinking part, having areas for impulses from sensory receptors,i.e., hearing, smell, sight, etc., and reparate areas of association where sensory informationis interpreted and motor areas to control voluntary muscles.

(b) Midbrain. Plays some role in hearing, sight and involuntary actions.

(c) Hindbrain. Three main parts of hindbrain are:

! Cerebellum. Which controls posture, balance of body and accurate voluntary movements.

! Pons. Regulates respiration.

! Medulla oblongata. It control involuntary actions like blood pressure, salivation,vomiting, etc.


26. (a) Limewater turns milky when CO2 is passed through limewater.

(b) Na2CO3 + 2HCl (dil.) → 2NaCl (aq) + H2O (1) + CO2(g)

(c) When the evolved gas is passed through limewater, limewater turns milky.

Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (1)

Limewater Carbon Calcium Water

dioxide carbonate

(d) When sodium hydroxide is taken in test tube A, it neutralises dil. hydrochloric acid, formingsalt sodium chloride and water.

2NaOH + 2HCl(dil.) → 2NaCl(aq) + 2H2O(l)

27. (d) 28. (b) 29. (d) 30. (d) 31. (b) 32. (b)

33. (b) 34. (d) 35. (c) 36. (c) 37. (b) 38. (b)

39. (d) 40. (b) 41. (c) ""

98 XS C I E N C E

PRACTICE PAPER-V

1. Transport of food from leaves to other parts of the plant is called translocation.

2. Resistance of a conductor increases with increase in temperature.

3. 1 volt = 1 joule/1 coulomb.

Potential or potential difference.

4. Iron objects acquire reddish brown coating on exposure to moist air, due to formation ofhydrated oxide of iron formed by rusting of iron. Chemical process responsible for theformation of reddish coating is rusting and the red coat formed is hydrated oxide ofiron/rust.

5. When copper is heated in oxygen of air, copper gets oxidised to copper oxide which is blackis colour.

6. A nerve impulse is an electrochemical signal travelling through a neuron.

Transmission of information impulse. Information from the environment is detected bydendritic tip of a neuron located in the sense organ. A chemical reaction sets off here and itcreates an electrical impulse which travels from dendrite to cell body and then along theaxon to its endings where it sets off the release of some chemicals. The chemicals cross thesynapse and set off a similar electrical impulse in dendrites of next neuron. Another synapseat the end of its axon delivers the impulse to the other cells like muscles cells/glands(effector organs) which react to perform the action.

7. No two magnetic field lines are found to intersect each other because if they did, thesewould be two directions at one point which is not possible.

8. (d) The direction of force is perpendicular to the direction of magnetic field and current isgiven by Fleming's left hand rule. As we know, the direction of current is taken oppositeto the direction of motion of electrons. The force is, therefore, directed into the page.

9. Some of the criteria for selecting a good fuel are:


(b) low cost;


(d) a high calorific value;


(f) no combustion products that are poisonous or environmental pollutants.



11. (a) When baking soda is used for baking purposes, on heating at high temperature, itdecomposes and evolves carbon dioxide gas. This carbon dioxide gas evolved helps thecake to rise and makes it soft and spongy.

(b) Its pH is more than 7.

12. (a) In test tube A hizzing occurs more vigorously because HCl is stronger acid than aceticacid and thus a faster reaction takes place with HCl.

(b) Mg (s) + 2HCl (dil.) → MgCl2 (aq) + H2 (g)Mg (s) + 2CH3COOH (aq) → (CH3COO)2 Mg (aq) + H2 (g)

13. (a) Oxide formed is amphoteric in nature.

(b) The metal X is zinc and the formula of its oxide is ZnO.

14. (a) Sodium oxide, potassium oxide.

(b) Alkalies.

15. This is because the blood flows twice through the heart before it is pumped throughout thebody. Double circulation consists of the following events:

(a) Deoxygenated blood from large veins called vena cava pours into the right atrium whenmuscles of all four chambers of heart are relaxed. This comes from the tissues.

(b) Pulmonary veins from lungs pour oxygenated blood into the left atrium.

(c) Atria contract and blood is poured into the respective ventricles. Right ventricle hasdeoxygenated blood and left ventricle has oxygenated blood.

(d) Now, the ventricles contract and right ventricle pumps deoxygenated blood to the lungsthrough pulmonary artery and left ventricle pumps oxygenated blood to all parts ofblood through aorta.

(e) Thus, deoxygenated blood comes to heart, oxygenated in the lungs and again comesback to the heart and then sent to all other parts.

16. Mechanism of inhalation:

(a) The diaphragm and rib muscles contract which make the thorax move upwards andoutwards.

(b) The volume inside the thoracic cavity increases, i.e., it expands.

(a) Air pressure inside the thoracic cavity decreases. Thus, air from outside rushes into thelungs/alveoli through nostrils, tracheae and bronchi.

17.

100 XS C I E N C E

18.

19. (a) Effective resistance (R) = 100 + 200

= 300 Ω.

(b) I = VR =

12300 = .04 A

(c) Potential difference (P.D.)

= P.D100 Ω

= 12 × 100 = 50 V.

Similary, P.D200 Ω = 12 × 200

= 100 V.

20. (a) Compressed Natural Gas.

(b) When the resistance is doubled, the current gets halved.

21. (a) Nitric acid is a strong oxidising agent. Thus, when a metal reacts with nitric acid, the H2gas produced is oxidised to water by nitric acid and it itself gets reduced to any of theoxides of nitrogen (NO2, N2O).

(b) Sodium metal is a highly reactive metal which vigorously reacts with oxygen present inair if kept in open and catches fire. Thus, to prevent its reactivity and prevent accidentalfires it is kept immersed in kerosene oil.

(c) The reaction of Fe2O3 with aluminium is a highly exothermic reaction. In this reaction,aluminium reduces iron oxide to produce iron metal with the evolution of lot of heat.Due to this heat, iron metal is produced in molten state. The molten iron is pouredbetween the broken iron pieces to join them.

22. (a) Lower is the pH of the substance, higher is its acidic strength. Therefore, a substancehaving pH of 2.4 has higher acidic strength while pH of 6.8 has lowest acidic strength.Thus, the increasing acidic strength is B > A > C.


(b) Plaster of Paris (CaSO4. 12

H2O) has a strong tendency to absorb moisture and gets

converted into gypsum (CaSO4.2H2O) which sets into a hard mass. Thus, to prevent itscontact with moisture, it is stored in moisture proof container.

(c) The formation of H+ ions is responsible for the acidic properties of the substance. Sinceacids cannot furnish H+ ions in the absence of water, they cannot show acidic properties.

23. (a) Insoluble product is lead iodide, which is yellow-coloured.

(b) Pb(NO3)2 (aq) + 2KI (aq )→ PbI2 ↓ + 2KNO3 (aq)

24. Resistivity is defined as the resistance of a conductor of unit length and unit area ofcross-section.

As we know, R = ρlA

or R = ρ l d2× 4

π

or R =9

3 2

1.2 ×10 ×1.2×43.14× (4× 10 )

=9

6

1.2 ×10 ×1.2×43.14× 16× 10

=30.3 ×10 ×1.2

3.14

=30.36 ×10

3.14

= .11 × 103 Ω.

25. (a) Endocrine glands. The glands which do not have ducts to pass their secretions calledhormones, so they are also called ductless glands.

(b) The two endocrine glands present in the human brain are pituitary and hypothalamus.

(c) Functions of the hormones:

(i) Tropic hormones. Regulate the secretions of hormones of the other endocrine glands.Tropic hormones are secreted by the pituitary gland.

(ii) Vasopressin. It is a hormone of pituitary gland which regulates water and electrolyticbalance in the body.

(iii) Adrenaline. Regulates blood pressure and heartbeat rate.

(iv) Insulin. Lowers the blood glucose.

(d) Two characteristics of hormones are:

(i) They are poured directly into the blood which transports them during its circulation.

(ii) They act on specific tissue/organ called target organ.

102 XS C I E N C E

26. (a) ZnCO3 (Ore of zinc)


Calcination for conversion of ore to oxide formby heating it in the absence of oxygen.



Reduction using coke as reducing agentZnO + C → Zn + CO

Refining of metal to obtain pure metal

(b) Cinnabar ore(HgS)


Roasting for conversion of ore into oxide formby heating it in the presence of oxygen

2HgS + 3O2 ∆→ 2HgO + 2SO2

2HgO ∆→ 2Hg + O2

Mercury metal

Refining of the metalto obtain pure metal

27. (c) 28. (d) 29. (b) 30. (d) 31. (a) 32. (c)

33. (d) 34. (c) 35. (b) 36. (c) 37. (c) 38. (c)

39. (a) 40. (a) 41. (c)

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