SET 1 Perfect Score 08 FINAL

7/28/2019 SET 1 Perfect Score 08 FINAL

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Set 1 Chemistry Perfect Score Module 2008PAPER 2 STRUCTURE

SECTION A

1 Graph 1 shows the temperature against time of solid substance X when heated. Substance X is anorganic compound and flammable.

GRAPH 1

(a) Draw a diagram of the set-up of the apparatus used to determine the melting point of substance X.

[ 2 marks](b) (i) State the melting point of substance X

........................................................................................................................................................[ 1 mark]

(ii) What is the state of matter of substance X at :

PQ : .....................................................................................................................................................

RS : ....................................................................................................................................................

[ 2 marks]

(iii) Explain why the temperature remains constant from Q to R.

..............................................................................................................................................................

..............................................................................................................................................................[ 2 marks]

(iv) State how the movement of substance X particles changes between R and Sduring heating.

[ 1 mark]

Set 1 1

Temperature / 0C

Time/s

80

3

0

36

0

P

Q R

S


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Set 1 Chemistry Perfect Score Module 2008(c) If substance X is cooled to the room temperature without stirring, draw the graph of temperature against

time obtained.

[ 2 marks](d) Identify subtance X

.....................................................................................................................................................................[ 1 mark]

2 Diagram 2 shows part of the Periodic Table of Elements.V,W,X,Y and Z do not represent the actualsymbol of the elements.1 18

2 13 14 15 16 17

W X V Z

Y

DIAGRAM 2(a) Write the electron arrangement of V ion.

.....................................

[1 mark](b) (i) Which of the element is not chemically reactive.

. ...........................................................................................................................................[1 mark]

(ii) Explain your answer in (b)(i).

...........................................................................................................................................[1 mark]

(c) V and Y are located in the same group in the Periodic Table of Elements.(i) Which of the element is more reactive?

.......................................................................................................................................[1 mark]

(ii) Explain your answer in (c)(i).

......................................

......................................

......................................[3 marks]

(d) Y reacts with iron to form a compound.

(i) State one property of the compound formed.

........................................[1 mark]

Set 1 2


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Set 1 Chemistry Perfect Score Module 2008(ii) Draw a labeled the set up of apparatus of the reaction between Y and iron, Fe

[ 2 marks]

3 The table 3 shows melting point, boiling point and electrical conductivity of substance P, Q, R, and T .

\SubstanceMelting point (oC) Boiling point (oC )

Electrical conductivity

Solid Molten

P 805 1460 No Yes

Q 1549 2950 Yes Yes

R -210 -153 No No

T -7 59 No No

Table 3(a) Which of the substances is a metal ?

.[1 mark]

(b) (i) state the type of particle in substance P ?

..[1 mark]

(ii) Explain why substance P cannot conduct electricity in solid but can conduct electricity molten state.

..................................................................................................................................................................

..................................................................................................................................................................[2 marks]

(c) (i) What is the physical state of R and T at room temperature ?

R : ............................................

T : ...................................... [2 marks]

(ii) Draw the arrangement of particles in substance T at room temperature .

[ 2 marks ]

Set 1 3


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Set 1 Chemistry Perfect Score Module 2008(iii) Explain why the melting and boiling points of substance R and T is low ?

.

[ 2 marks ]

4 The diagram 4 shows the electron arrangement of compound J. Compound J formed from reactionbetween element X and element Y

__ 2 + __

Y Y X Y

Diagram 4

(a) How are Y ion and X ion formed from their respective atoms?

Y ion: ..

X ion : [ 2 marks]

(b) (i) Write the formula for compound J

........................................................................................................................ [1 mark]

(ii) Name type of bond in compound J

........................................................................................................................ [1 mark]

(iii) Write the chemical equation for the reaction between element X and element Y to formcompound J.

..............................................................................................................................................

[1 mark]

(c) (i) Write the electron arrangement for atom of element X and Y

X :.

Y : .. [2 marks]

(ii) Between atom of element X and Y, which one has a smaller size.

.........................................................................................................................................

[1 mark]

(iii) Explain your answer in (b) (ii)

..........................................................................................................................................

..........................................................................................................................................

[3 marks]

Set 1 4


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Set 1 Chemistry Perfect Score Module 2008(d) Y can react with carbon to form a compound. Draw the electron arrangement for the

compound formed.[Given that proton number for carbon is 6]

[2 marks]

5 In an experiment to determine the empirical formula of an oxide of copper , the combustion tube withthe porcelain dish are weighed. Oxide of copper is added into the porcelain dish and the tube isweighed again. The oxide of copper is heated strongly. After the set of apparatus cools down to roomtemperature the combustion tube with its content is weighed again.

The following data is obtained.

Mass of combustion tube + porcelain dish = 19.60 gMass of combustion tube + porcelain dish + oxide of copper = 25.68 gMass of combustion tube +porcelain dish + copper = 24.46 g

(a) What is meant by empirical formula?

[1 mark]

(b) Draw a labeled diagram of the set-up of the apparatus for the experiment.

[2 marks](c) Calculate the empirical formula of the oxide of copper.

[Given that the relative atomic mass of O=16 , Cu=64]

[3 marks](d) Write the chemical equation for the reaction in the experiment.

....................................[1 mark]

Set 1 5


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Set 1 Chemistry Perfect Score Module 2008(e) Before oxide of copper is heated, hydrogen gas is allowed to pass through the apparatus until

all the air in the combustion tube is completely removed.Describe the steps that should be taken to ensure that all air in the combustion tube has beenremoved.

[3 marks]

(f) (i) Can the empirical formula of magnesium oxide be determined using the same method asabove? Explain your answer.

.....................................

.....................................[2 marks]

(ii) Draw a labeled diagram of the set-up of the apparatus for the experiment

[2 marks]6. Diagram 6 shows shows the chemical symbols which represent elements R, S and T.

R S TDiagram 6

(a) (i) Write the electron arrangement of atom T

[ 1 mark]

(ii) State the period and the group for element T in the Periodic Table.

Period : ...................................................

Group : ...........................................................[2 marks]

(b) Atoms of R and S can react to form a compound.

(i) Name the type of bond in the compound formed between atoms R and S.

[1 mark]

(ii) State one physical property of the compound formed in b(i)

..[1 mark]

Set 1 6

17 6 11

35 12 23


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Set 1 Chemistry Perfect Score Module 2008

(c) (i) Atom of R and T can also react to form compound. Draw the electron arrangement for thecompound formed.

[2 marks](ii) Name the force that exist between particles in the compound formed .

........................................................................................................................................................[ 1 mark]

(iii) The melting point of the compound formed is 801 C and its boiling points is 1413 C. What is testate of matter for this compound at 1000 C.

..........................................................................................................................

...................[ 1 mark]

(d) Arrange R, S and T according to the increase the atomic size

[1 mark]

7 Lactic acid is an acid produced in milk by bacteria that causes the milk to taste sour. Table 7 showsthe percentage of composition by mass of each element in lactic acid.

Element Percentage

Carbon 40.00Hydrogen 6.67

Oxygen 53.33

TABLE 7

(a) Based on the information above, calculate the empirical formula of lactic acid.Given that the relative atomic mass of H = 1 ; C = 12 ; O = 16

[3 marks](b) Relative molecular mass of lactic acid is 90. Determine the molecular formula of lactic acid.

[2 marks](c) Calculate the number of hydrogen atom in 1 mol of lactic acid?

Given that Avogadro number ,NA = 6.02 1023 mol-1

[2 mark]

(d) Calculate the number of moles of 4.5 g lactic acid.Given that the relative atomic mass of H = 1 ; C = 12 ; O = 16

Set 1 7


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Set 1 Chemistry Perfect Score Module 2008[1 mark]

(e) Vinegar or ethanoic acid has a similar empirical formula with lactic acid.

(i) Given that three molecules of ethanoic acid have the same mass as two molecules of lacticacid. What is the relative molecular mass of ethanoic acid?

[1 mark](ii) Determine the molecular formula of ethanoic acid.

[2 marks]

8 Table 8 shows formula of four ions.

Name of ions Silver ion Zinc ion Nitrate ion Chloride ion

Formula of ions Ag

+

Zn

2+

NO3-

Cl

-

TABLE 8(a) Write the formula for each compound below :

(i) Silver nitrate ............................................................................................

(ii) Zinc chloride : .......................................................................................................

(ii) Silver chloride : .......................................................................................................

(iii) Zinc nitrate : .......................................................................................................[4 marks]

(b) When silver nitrate solution is added to zinc chloride solution, white precipitate, silver chloride and

zinc nitrate solution are formed.

(i) Identify the reactants and products of the reaction.

Reactants : .......................................................................................................................

Products : .......................................................................................................................[2 marks]

(ii) Write the chemical equation for the reaction occurs in (b).

...........................................................................................................................................[1 mark]

(c) The following equation shows the decomposition of silver nitrate by heat.

2AgNO3 2Ag + 2NO2 + O2

If 85.0 g of silver nitrate is heated completely, calculate :(i) the mass of silver formed.

Given that the relative atomic mass of N =14; O = 16; Ag =108

[3 marks](ii) the volume of oxygen gas formed at room conditions.

Given that the Molar volume:24 dm3 at room conditions

Set 1 8


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Set 1 Chemistry Perfect Score Module 2008[2 marks]

ESSAY SECTION B9 (a) Diagram 9 shows the models of atoms which were developed by Ernest Rutherford and Neils Bohr

and modern atomic model.Electron moves outside thenucleus

Nucleus contains protons

Rutherfords model Bohrs modelDIAGRAM 9

(i) Describe th atomic structure of the Bohrs model [4 marks]

(ii) What is the difference in the position of electrons between the Rutherfords model and Bohrsmodel

[2 marks](iii) Draw the electron arrangement of an atom that consist of 13 electrons using the modern atomic

model[2 marks]

(b) Chlorine has two isotopes which are chlorine-35 and chlorine-37.The proton number of chlorine is 17.X

(i) Write the symbol forone of the isotope of chlorine in the form of AZ [3 marks]

(ii) Compare the number of sub atomic particles in these two isotopes[4 marks]

(c) Describe fully the atomic structure for chlorine isotope that you have stated in 1(b)(i)[5 marks]

ESSAY SECTION C

10 (a)

Explain the above statement.Given that relative molecular mass of carbon dioxide = 44 g mol 1,relative molecular mass of oxygen = 2 g mol 1

[3 marks]

(b) (i) What is meant by empirical formula? [ 1 mark]

(ii) Describe an experiment in the laboratory to determine the empirical formula ofmagnesium oxide. Your answer should consist of the following.

Procedures of the experiment

Calculation involved

Precautions need to be taken

Given that relative atomic mass of Mg = 24, O = 16[13 marks]

(c) Magnesium can reduced copper oxide to copper.Explain why the empirical formula of the copper oxide cannot be determined by heating themixture of copper oxide and magnesium powder.

[ 3 marks]

Set 1 9

The volume of 2.2 g of carbon dioxide gas is less thanthe volume of 2.2 g of hydrogen at the same temperature and pressure.

Electron

Shell

Nucleus containsprotons

Modern

atomic

structure


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11 Table 11 shows the proton number of atoms P, Q and R.

Element P Q R

Proton number 8 12 17

TABLE 11(a) Based on electron arrangement, explain the formation of chemical bond between

(i) element P and element P [5 marks ](ii) element Q and element R

[7 marks ](b) Gas P reacts with element Q to produce a white solid.

(iii) Write a chemical equation for the reaction between gas P and element Q.(ii) State three physical properties of the white solid. [ 4 marks]]

(c) What is the position of elelment Q in the Periodic Table of the elements?Explain how do you obtain your answer. [ 4 marks ]

PAPER 312. The diagram below shows the apparatus set-up for the experiment to determine the freezing point of

substance X.

The diagram below shows the thermometer reading for the cooling of substance X at certain timeintervals.

Set 1 10

thermometer

Substance X

Volumetric flask

90

95

85

0 Minute 1st minute 2nd Minute 3rd minute

85

90

80

85

90

80

85

90

80

85

90

85

90

80

75

80

70

70

75

65

4th minute 5th minute 6th minute 7th Minute


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(a) Record the thermometer readings shown in the diagram above by completing the table below.

[3 marks](b) Draw the graph of temperature against time on the graph paper provided.

[3 marks](c) Based on the graph in (b),

(i) State the change in temperature of substance X for the whole experiment.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... [3 marks](ii) State the inference for your answer in (c) (i) .

...........................................................................................................................

...........................................................................................................................[3 marks]

(d) What is the freezing point of substance X? Show and label it on the graph how you obtained theanswer.

............. [3 marks](e) Based on this experiment, what is meant by freezing point?

...

... [3 marks]

(f) If substance X is heated from room temperature until 100oC, what is the temperature whensubstance X starts to melt? Explain your answer.

.......................[3 marks]

13

An experiment is carried out to investigate the statement above.The table below shows the apparatusset up and the observations for the experiment to determine the reactivity of the Group 1 elementsbased on their reactions with water.

Apparatus set-up Observation towards the metal

Lithium moves slowly on the surface of the waterwith a hiss sound.

Set 1

time/minute 0 1 2 3 4 5 6 7

Temperature/ oC

11

Elements in Group 1 of the Periodic Table of Elements can be arranged based on thereactivity of the elements with water.

water

Lithium


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Potassium moves vigorously and randomly on thesurface of the water with a hiss sound.

Sodium moves quickly and randomly on thesurface of the water with a hiss sound.

(a) State the variables that are involved in the experiment.

Name of variables Action to be taken

(i) Manipulated variable:

..

..

(i) The way to manipulate variable:

..

...

(ii) Responding variable:

(ii) What to observe in the responding variable:..

..

(iii) Controlled variable:

..

..

(iii) The way to maintain the controlled variable:

[6 marks]

(b) State one hypothesis for the experiment.

[3 marks]

(c) Based on the observations in the figure above, arrange lithium, potassium and sodium in thedescending order of reactivity of metals towards water.

Descending order of reactivity of metals towards water.[3 markah]

(d) Solution X was produced from the reaction of sodium with water. Classify the ions that exist insolution X into positive ions and negative ions.

Positive Ions Negative Ions

[3 marks]

Set 1 12

water

water

sodium

)) )

)))

Potassium

)) ) )


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When lithium metal is put in water, it moves very slowly on the surface of the water. When sodiummetal is put in water, it moves quite fast and produces hiss sound. When potassium metal is put inwater, it moves very fast and produces small explosions.

Metal


14

Plan an experiment in the laboratory to investigate the reactivity of lithium, sodium and potassium with waterand describe the effect of the solution produced towards a red litmus paper.The planning of your experiment must consist of the following:

(a) Aim of experiment(b) Statement of the hypothesis(c) All the variables(d) List of substances and apparatus(e) Procedure of the experiment(f) Tabulation of data

[17 marks]

Set 1 13

Water


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Set 1 Chemistry Perfect Score Module 2008SampleAnswer

Section A

1 (a)

[Functional diagram ]

[ Labeled] 11

(b) (i) 80 oC 1

(ii) PQ : solidRS : liquid

11

(iii) The energy is absorbedto overcome the forces of attraction between the particles

11

(iv) The particles move faster 1

(c)

[The shapeof the graphis correctand 80 0C on graph]

[ Both axis are labeledwith unit]

11

(d) naphthalene 1

11

2 (a) 2.8.8 1(b) (i) Z 1

(ii) Achieve octet electron arrangement // achieve 8electron in the outermost shell // 8 valence electron 1

(c) (i) V 1

(ii) The atomic size of V is smaller than the atomic size of Y 1

The attraction between the nucleus and the outermost occupied shellis stronger in an atom V than an atom Y 1

It is easier for atom V to receive electron 1

Set 1 14

Temperature / 0C

Time/s

80

Boiling tube

Heat

Substance X

water

Thermometer


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Set 1 Chemistry Perfect Score Module 2008(d) (i) High melting / boiling point// dissolve in water// do not dissolve in

organic solvents // conduct electricity in aqueous solution or molten state 1

(ii)

Functional diagram and heating is shown 1Y/Chlorine gas and iron labeled 1

103 (a) Q 1

3(b)(i) Ion 13(b)(ii) solid state : Ions are not freely moving// ions are in a fixed position.

molten state : Ion can move freely

1

13(c)(i) R : Gas

T : Liquid1

3(c)(ii)2

3(c)(iii) - Van der waal/intermolecular forces are weak- Small amount of heat is required to overcome it

11

Total 10

4 (a) Atom Y receive one electronAtom X receive two electron

11

(b) (i) X2Y 1

(ii) Ionic bond 1

(iii) 4X + Y2 2X2Y 1

(c) (i) X : 2.8.2Y : 2.8.7

11

(ii) Y 1

(ii) - Atom X and atom Y have the same number of shells occupy with electrons- The number of proton in the nucleus of atom Y is more than X- Nulcei attraction to the electrons in the shells of atom Y is stronger than X

111

(d) - Electron arrangement all atoms are correct- One carbon atom share four pairs of electrons with 4 Y atoms

11

Total 12

5 (a) Formula that shows the simplest ratio of the number of atomsfor each element in the compound. 1

Set 1 15

Y/Chlorine gas

Iron

Heat


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(b)

Functional diagram an heating is shown 1Dry hydrogen gas and oxide of copper are labelled 1

(c) Cu O

24.46 19.60 / 4.86 25.68 24.46 / 1.22 1

4.86 / 0.076 1.22 / 0.076 164 16

CuO 1

(d) CuO + H2 Cu + H2O 1

(e) Collect the gas in a test tube 1Put lighted wooden splinter at the mouth of the test tube 1No pop sound 1

(f) (i) No 1Magnesium more reactive than hydrogen //Hydrogen less reactive than magnesium // hydrogen belowmagnesium in reactivity series. 1

(ii)

Functional diagram and heating is shown 1Magnesium is labeled 1

14

6 (a) i 2.8.1 // 2,8,1 1

ii 31

11

(b) i Covalent bond 1

ii Low melting point and boiling point//insoluble/does not dissolve in

water//soluble/dissolve in organic solvent//does not conduct electricity in any stateChoose one

1(c) (i)

Number of electrons for ion T and ion R are correctCharge of ions and ratio of ion T to ion R are correct

11

(ii) Elecrostatic 1

(iii) Liquid / molten state 1

Set 1 16

R

-+

T

Dry hydrogen gas

Oxide of copper

Heat

Heat

Magnesium


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Set 1 Chemistry Perfect Score Module 2008(d) S, R,T 1

Total 10

7 (a)

Element C H O

Number of moles(mol) 12

00.40

= 3.33

1

67.6

= 6.67

16

33.53

= 3.33

Ratio of moles 1 2 1

1

1

The empirical formula of the compound is CH2O 1(b) n [ 12 + 2(1) + 16 ] = 90

n =30

90

= 3

Molecular formula of lactic acid is C3H6O3

1

1(c) One molecule of lactic acid contains 6 hydrogen atoms//

1 mol of lactic acid contains 6 mol of hydrogen atoms1 mol of lactic acid contains 6 6 .02 10 23 hydrogen atoms

11

(d)The number of mole of lactic acid =

90

5.4

= 0.05 mol1

(e) 3 Mr of ethanoic acid = 2 Mr of lactic acid

Mr of ethanoic acid =3

902 x

= 601

(f) n (30) = 60n = 2

Molecular formula of ethanoic acid is C2H4O2 / CH3COOH1

111

8 (a) (i) AgNO3 1

(ii) ZnCl2 1(iii) AgCl 1(iv) Zn(NO3)2 1

(b) (i) Silver nitrate and zinc chloride 1

Silver chloride and zinc nitrate 1

(ii) 2AgNO3 + ZnCl2 2AgCl + Zn(NO3)2 1(c) (i)

Number of moles of AgNO3 =170

85

= 0.5 mol1

2 moles of AgNO3 produce 2 moles of Ag0.5 mole of AgNO3 produce 0.5 mole of Ag 1Mass of Ag = 0.5 108

= 54 g 1(ii) 2 moles of AgNO3 produces 1 mole of O2

0.5 mole of AgNO3 produces 0.25 mole of O2 1Volume of O2 = 0.25 24

= 6 dm3 1

10

SECTION B9 (a) (i) 1. Atom consist proton and electron 1

2. Electrons in the shell 1

Set 1 17


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Set 1 Chemistry Perfect Score Module 20083. Protons are in the nucleus 14. The nucleus in the middle of the atom 1

(ii) 1. Rutherfords model: Electrons outside the nucleus 12. Bohrs model: Electrons in the shell 1

(iii)

1. Atom with nucleus and the number of shells is 3 12. Correct number of electrons: 2.8.3 1

(b) (i) 35 37Cl Cl

17 171. Symbol of an element 12. Nucleon number 13. Proton number 1

(ii) 1. Chlorine-35 and chlorine-37 have 17 protons// The electron arrangements ofchlorine-35 and chlorine- 37 are 2.8.7 1

2. The number of neutron in chlorine-35 and chlorine- 37 are 18 and 20 respectively//The nucleon number of chlorine-35 and chlorine- 37 are 35 and 37 respectively 1

(c) 1. Nucleus is at the centre of the atom2. Nucleus contains 17 protons, which are positively charged particles3. The number of neutrons are 18/20 which are neutral particles4. The nucleon number is 35/375. Electron cloud consist of 17 electrons6. Electron which is negatively charged particles move around the

nucleus// Electron is located outside the nucleus/in the shell7. Electron arrangement is 2.8.7// The number of shells field with electrons are 3 any 5

Total: 20SECTION C

10 (a) Number of mole of carbon dioxide =44

2.2= 0.05 mol 1

Number of mole of hydrogen =2

2.2= 1.1 mol 1

The number of mole of carbon dioxide is smaller; therefore, its volume is smaller thanthe volume of hydrogen 1

(b) (i) The empirical formula of a compound is the formula that shows the simplestwhole number ratio of atoms of each element present in the compound. 1

(ii) [Material and apparatus]

[Magnesium ribbon, sand paper, crucible with lid, tongs, Bunsen burner, tripod stand, pipe-claytriangle and balamce.] or [diagram] 2[Procedure]

A crucible and its lid is weighed and its weight is recorded. 1

A 10 cm length of magnesium ribbon is coiled loosely and is placed in the crucible. 1

The crucible with its lid and content are weighed again and the weight is recorded . 1

The crucible is heated strongly without its lid. 1

When the magnesium starts to burn, the crucible is covered with its lid.

Using a pair of tongs, the lid is lifted at intervals. 1

When the burning is completed, the lid is removed and

the crucible is heated strongly for 2 minutes. 1

The rucible is allowed to cool to room temperature. 1

The crucible and its lid and content are weighed again and its weight is recorded. 1max 5

[Precautions taken]

Set 1 18


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Set 1 Chemistry Perfect Score Module 2008 The magnesium ribbon is cleaned with sand paper to remove the layer of

magnesium oxide on the surface.

The crucible must cover with its lid to prevent the white fumes of

magnesium oxide of escaping.

The processes of heating, cooling and weighing are repeated until

a constant mass is obtained. [any two of the above] 2

[ Results]

Crucible + lid = a g

Crucible + lid + magnesium = b gCrucible + lid + magnesium oxide = c g 1

[ Calculation ]

Element Magnesium Oxygen

Mass(g) b-a c-b

Number of moles of atoms b-a/24 c-b/16

Simplest ratio of moles X y

2Empirical formula = MgxOy 1

(c) 1 Unable to make sure that all the magnesium is oxidised . 12 The products (Cu and MgO) cannot be separated. 13 The mass of copper and oxygen cannot be determined. 1

2011 (a)(i) 1. Two atoms of P combine through covalent bond. 1

2. Each atom of P needs two more electrons to achieve octet electron arrangement.3. Each atom of P contributes two electrons to each other for sharing. 14. Two atoms of P share two pairs of electrons. 15. A double covalent bond is formed.

P P

2

(ii) 1. Atom Q and atom R combine through ionic bond. 12. To achieve octet electron arrangement, 13. atom Q with 6 valence electrons loses two electrons to form Q2+ ion 14. Two atom R, each atom with 7 valence electrons

gains one electron to form R- ion. 15. Q2+ ion and R- ion are attracted to each other by strong electrostatic force.1

_ 2+ _

R Q R

2

(b)(i) 2Q + P2 2QP 1

(ii) 1. Have high melting point 12. Usually soluble in water 13. Conduct electricity in the molten state or aqueous solution. 1

Set 1 19


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1. Element Q is located in Group 2 12. because it has two valence electrons 13. Element Q is located in Period 3 14. because it has three shells occupied with electrons 1

20PAPER 3

Question Rubric

12 (a) Able to record all the readings correctly to 1 decimal place.

Time(minute)

0 1 2 3 4 5 6 7

Temperature(oC)

95.0 89.0 84.5 83.0 83.0 83.0 77.0 70.0

12 (b) Able to draw the graph with the following elements::

X-axis is labeled(minute) and y-axis temperature(oC) with consistent scales

Size of the graph is at least half the page of the graph paper.

All the points are plotted correctly

Curve of the graph is correct and smooth

Set 1 20

Temperature/oC

Melting point

Graph of temperature against time


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Question Rubric

12 (c) (i) Able to explain the change of temperature with time from the graph.Suggested answer:

In the first 3 minutes, the temperature of substance X will decrease from

95oC to 83oC.

Constant temperature at 83 oC for 3 minutes.

The temperature decreases again after 83 oC12 (c) (ii) Able to make the correct inference.

Suggested answer:

Temperature decreases because heat is released to the surrounding.

Temperature is contant because heat released to the surrounding is

balanced by the heat released when bonds are formed.

The freezing process is at 83 oC // solid and liquid X exist together

12 (d) Able to state the freezing point accurately based on the graph with the

correct unit. Dotted line is shown on the graph.

Labeling the freezing point at temperature axis.

12 (e) Able to give the meaning of freezing point accurrately.Suggested answer:Freezing point is the constant temperature at 83oC even though substance X islet to cool to room remperature.

12 (f) Able to predict the melting point of substance X accurately with unit and withcorrect reasons.Suggested answer :83.0 oCValue of melting point substance X is the same as its freezing point.

Question

Rubric Rubric

13 (a) Able to predict the manipulatedvariable, the responding variable andthe constant variable completely.

Suggested answer:Manipulated variable : metals ofGroup 1 elements // sodium, lithium,potassium.

Responding variable: the reactivity ofthe reaction with water // the speed ofmovement on the water surface

Constant variable: size/mass ofmetals. Volume of water

Able to state how to control the manipulatedvariables correctly

Suggested answer:Repeat the experiment by using the metals ofsodium, lithium and potassium

Able to state correctly the way to control themanipulated variable

Suggested answer:To observe how fast the metals move on thesurface of water.

Able to use the metal granules with the same sizeSuggested answer :Use the metal granules with the same size.

13 (b) Able to state the relationship between the manipulated variable and the responding

variable correctly..

Suggested answer: The reactivity of Group 1 elements increases going down the group.

13 (c) Able to arrange correctly the reactivity series of the metals according to descending order.Answer: potassium, sodium, lithium

13 (d) Able to classify the ions correctly.[to name or write all the formula of the ions correctly at the cations and anions group.]

Set 1 21

Time/minute


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Set 1 Chemistry Perfect Score Module 2008Answer: positive ion/ cation : sodium ion/ Na+, hydrogen ion/ H+

Negative ion/anion : hydroxide ion/ OH-

Question Rubric Score

14(a) [Able to state the aim of experiment accurately]To compare the reactivity of lithium, sodium and potassium based on thereaction with water and describing the effect of the solution towards thered litmus paper.

3

14(b) Hypothesis

Metals of lithium, sodium and potassium show different rate of reactivitywith water and the solution formed turns red litmus paper to blue.

14(c) Variablesa) Manipulated variable :type of metalsb) Responding variable : reactivity of reactionc) Constant variable : water and temperature

3 x12x11x1

14(d) [Able to list the correct and complete substances and apparatus.]Substances and Apparatus

Lithium, sodium and potassium metals with water, basin, knife, forceps,blue litmus paper and white tile.

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14(e) [Able to give all the procedures correctly, steps 1 - 7]

1. Lithium metal is cut into a small piece2. The paraffin oil on the surface of the metal is wiped with the filter.3. A basin is filled with water.4. Lithium metal is put on the surface of the water with a pair of forceps.5. Reactivity of the reaction is observed and recorded.6. The experiment is repeated with sodium and potassium metals.

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14(f) [Able to show the accurate tabulation of data with correct title.]

Metals Observations

Lithium

Sodium

Potassium

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Documents

SET 1 Perfect Score 08 FINAL