Science experiments

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IMPORTANCE OF HANDS-ON ACTIVITY:

Science has become an integral part of human life. Application of science has providedmany benefits, and a better Quality of life. The world today uses a language which has a lot ofscience in it.

Without knowing, we use many words and phrases derived from science. We are alsobecoming conscious of our environment as well as our economy. Science has much to do withboth these aspects, not only children but adults alike have to know the principles of science andmust be able to use the language of science where necessary. They must be able to apply thelessons learnt from science in their daily life.

In 8th and 9th standard chapters like Food, Heat, Nature of light, Lens, Life processes,Chemicals in our daily life, Optical instruments, Motion, Circular motion, Gravitation, Laser,Electricity, etc. are need experiments to understand the concept.

When the Hands-on activity is given to students they made activity with very interest andresult is that all the student who undergone through activity they understood the basicknowledge. It helps to teach in the proper way.

As slogan “LEARNING BY DOING” students enjoy the learning.

Simple opportunity has been given to learner to think, read, discus and learn on their ownwith very little help from teachers. Learning is expected to be activity centered with the learnersdoing experiments.

So let us starts some Hands-on activities:

AIR AROUND US

The ancient Greek philosophers were sure that air contained only one substance andcalled it an element. Indian Philosophers also has the same idea and called it Vayu. Buteveryone agreed that the air around us was like an invisible ocean enveloping both the seas andthe land.

Air a mixture of gases: The Greek idea of air survived for many centuries. However, in 1770, Scheele, a Swedish scientist proved that air

Was not a single element. Was a mixture of active air and inactive air and The mixture had 80% inactive air and 20% active air.

But this was not end, Air is a mixture of gases: Nitrogen (N) -78% Oxygen (O) -21% Argon (Ar) -0.9% Carbon dioxide (CO2) – 0.03% Hydrogen (H), Ozone (O3), Helium (He), Water vapor -0.07%

S.V.BURLI, (STATE AWARDEE TEACHER) BANJARA HIGH SCHOOL, BANJARA NAGAR, BIJAPUR -586103

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AIR PRESSURE AND FLUID PRESSURE

Experiment No.1. Why don’t we feel the air pressure?

Air does not exert pressure only downwards or up wards. Air exerts pressure equally in all directions and on all surfaces.

Place clipboard on the table such that 1/4th of board must be outside of the table. If we

give pressure clipboard, it will fall. But if we spread a news paper on it after giving the same pressure to it now it will not fall.

Experiment No.2. Air Holds Paper.

Stretch your hand out, palm facingforward. With the other hand, press a papersheet on this palm, the paper falls down assoon as you release it. Again press the papersheet. But this time begin to run fast palmfacing forward. Paper will not fall.

When you run, Paper sheet pushes

against the air in front of your palm.In turn air also pushes the paperagainst your palm.

Experiment No. 3. Air resists at surface.

Hold two paper sheets of the same

size, horizontal, one in each hand.Raise your hands and release themfrom the same height. They fall withmore or less the same speed.

Now crumple one or them into a ball.

Again release a sheet and the ballfrom the height.

When the sheet falls, it pushes the air

below it and it turn air also pushes itup. As a result the sheet slows down.

When you crumple the sheet into a

Ball, its surface area reduces. So the air resistance also reduces.

Experiment No. 4. Bernoulli’s Bag: 1

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Cup both your hands and narrow

down the opening of the bag. Hold the opening of the bag to your

mouth. Blow in to the bag and countthe number of breaths required to fillthe bag. Try several times. Ask yourfriends also and count the number ofbreaths.

Now hold the opening about 15 cm.

away from your mouth and blow hardand long into the bag. Surprisingly,the bag gets filled with air, with justone puff.

Air pressure of a stream of air is less than the surrounding air. So the Surrounding air is also pulled into the stream.

1. Blow hard but steadily into a bendystraw. Still blowing put a ping-pongball over the shown in the picture.The ball gets trapped in the air streamand hovers in midair.

2. – Hold a paper strip (20cm*4cm) justbelow your lips (it drops down).

Now blow straight across it. The strip

rises up, gets horizontal and flutters. By blowing ,you speed up the air above

the strip. So air pressure above the striplowers down and air below the strip pushesit up.

3. – Make a hole in the middle of a smallPVC pipe. Hold the pipe such that thehole is about 1cm from a candle flame.-Blow steadily through the pipe; the flameis pulled towards the hole.

Experiment No. 5. Vacuum lift.

Fill the large test tube three-fourthswith water push the smaller test tubehalfway in it.Keep holding the outer test tube andinvert the setup. As water startscoming out through the clearancebetween the two test tubes, thesmaller test tube rises up.

Water falls down through a very narrow

clearance between the test tubes leaving nospace for air to enter. This creates a low-pressure area inside the large test tube. Theatmospheric air, which is at a higher pressure,forces the inner test tube up.


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HEAT

To keep your body warm during winteryou usually rub your palm. When youexercise vigorously your body gets warmer.So in ancient times people produced heat byrubbing two stones or wooden pieces whichled to the invention of fore. Heat is a form ofenergy.

Experiment No. 1. See Heat Flows!

Leaving 6-7 cm from one end of thespoke drop 4-5 drops of molten waxat an interval of about 1cm. Press theheads of 4-5 nails in to the wax to fixthem. Take precaution, molten waxmay burn you hands.Hold one end of the spoke to candleflame. Soon, the nail nearest to theflame falls and is followed by others.

When we heat a solid object at one point it

passes on heat to the surrounding particles.These particles also get hot and further passon heat to neighboring particles. Thisprocess continues until the entire object getsequally hot. This mode of transfer of heat iscalled ‘conduction’.

Experiment No. 2. Thread does notburn:

Tightly wrap 20-25 turns of threadaround the screwdriver’s metal partsuch that each turn makes goodcontact with the rod.Hold the threaded part over a flamefor 4-5 minutes. Unwrap and see; thethread has not burnt.

Iron is good conductor of heat. As thread

starts getting hot, its heat is conducted toiron. As no time the thread gets hot enoughto burn.

Wrap the thread around a wooden rod and seewhether the thread burns.


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Experiment No. 3. Paper dose not burn.

Wrap a piece of paper tightly around acoin. Hold it with pliers over a flame.See how long the paper takes to burn.

Explanation as same as the aboveexperiment.

Experiment No. 4 : Heat Water in papercup

Make a small paper cup using pins. Itshould hold water without leaking.Fill half of this cup with water andhold it over a candle flame. Take carenot to burn your fingers. To yoursurprise water gets hot but the papercup doesn’t burn.

Water absorbs most of the heat and

prevents the temperature of the paper cupto rise to its ignition point.

Here two properties of water must be

considered. First is the convection of heat. Water

molecules at the bottom absorb heat fromthe paper and rise up. Other coolermolecules take their place. They also absorbheat and go up. This process continues andprevents the paper cup from becoming toohot.

Second property of water is its high specific

heat. Due to high specific heat, even afterabsorbing much heat rise in its temperatureis small. Specific heat of a substance is theamount of heat needed to raise thetemperature of a gram of the substance by10c.

Experiment No. 5.Fire proof balloon.

Bring a light match near an inflatedballoon. It burnsts, even before theflame touches it.Now hold a water filled balloon overa candle flame (flame should touchonly the portion dontainingwater).Does the balloon burst? Seefor how long water can be heated.

When there’s no water inside the balloon,

the rubber of the balloon gets hot instantlyand melts.

When the rubber of water filled balloon

begins to heat up, it starts transferring heatto the water. This heat is dispersedthroughout the volume of water. So therubber coesn’t get hot enough to melt.

Experiment No. 6. Convectioncurrents.

Cut a hole of about one square cmnear one end of the pipe. Put the pipeover a lighted candle, with hole at thebottom. Hold some lighted agarbattisnear the hole. Smoke is sucked intothe hole and leaves the pipe from top.


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As air in the pipe gets heated, it becomes

lighter (density decreases) and rises up.Outside cooler air enters through the holeto take its place. In turn, this air also getsheated, rises up. Thus an sir current is setup which is called “convection current”

Wind is also an outcome of convection

currents. If the warm air does not rise up, any fire

would be surrounded by hot carbondioxide and would go out due to lack ofoxygen.

In liquids too, heat is transmitted by

‘convection’.

Experiment No. 7. Heat Expandswire.

Bend the spoke in a V-shape. Pull bothends a bit closer and fasten the copperwire taut between them. Rest apiece of refill should be placed suchthat is dislodges with the slightestincrease in the gap.Heat the wire. Within a couple ofminutes, the wire expands and therefill falls.

Molecules(or atom) of all substances are

in vibratory motion all the while. Evenwhile vibrating, the molecules of solidsmaintain their mean position. Whenheated, the molecules become moreenergetic and require more space tovibrate. This results is expansion.

Rails get heated due to friction and in

summer also. So gaps are left betweentheir joints.

VISION :

Experiment No.1. Coin disappears.

Place a coin in a bowl of water. Put aninverted glass over the coin; it disappears.

When light passes from a rarer (air) to a

denser (water) medium it bends towards thenormal and vice versa.

To reach your eyes, light rays from the

coin have to first pass from air ( in the glass)to water and then from water to air (outside).So they bend ‘down’ twice and are unable toreach your eyes.

The coin disappeared, but ha a void been

created there? Perform once again andobserve carefully. This question is discussedin the experiment “Disappearing picture”.

Experiment No 2.Coin appearsagain.

Place the coin in the bowl. Place yourself,from where you can see just the far edge ofthe coin. Move back yourself slightly; theedge of the bowl hides the coin. Now yourfriend pours water in to the bowl.Surprisingly, the coin is now visible.

When water is added, light from the coin

has to pass from water to air, so it getsrefracted. As a result, the rays that were


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earlier going above your eye level now benddown and reach your eyes. This makes thecoin visible, but now at a different location.

When you see a fish in water, you don’t

see the fish itself but you see its image. Thefish is actually slightly lower than its image.

When you first see the rising sun, it is

actually below the horizon. Earth’satmosphere refracts the sunlight and we seethe sun earlier.

Experiment No. 3. Total internalreflection.

To make light beam visible, add a fewdrops of milk in half a cup of water.From the side of the cup, point thelaser beam up, at the water surface.By increasing the angle of incidence,you may arrive at an angle when thebeam reflects back into water.

The angle of incidence at which the

refracted beam is along the interface iscalled the ‘critical angle’. Beyond thisangle, light is reflected back into water.This Phenomenon is called ‘total internalreflection’.

Experiment No. 4. Principle of fiberoptics.

Punch a hole near the bottom of thebottle. In a dimly lit room, point thelaser beam at the hole. Add a fewdrops of milk in water and pour it inthe bottle. The light now travels alongthe water stream. Put a finger in the

stream, and see a spot of light on youfinger.

In the water stream, light strikes the

interface between water and outside air atan angle more than the critical angle. So itis reflected back into the stream itself. Thisreflected beam too strikes the oppositesurface at an angle more than the criticalangle and is again reflected back. Thisprocess goes on and on.

Observe the beam making a wave like

pattern near the hole. Image you have a long tube-shaped, with

its reflecting surface on its inside. If youdirect a beam of light into the tube, itrepeatedly gets reflected until it reaches theother end. This would work, even if thetube were bent. The same thing happens inthe case of the water stream.

Experiment No. 5. Water prism.

Cover the windows with dark paper,leaving space for just a streak ofsunlight to enter the room.Place the mirror ina slanting positionin a bowl full of water. Position bowlto get a reflection of sunlight on awall. Adjust them properly; you get abeautiful rainbow on the wall.

Sunlight comprises many colors. While

refracting, different colors bend at differentangles. Red bends the least and violet bends


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the most. Hence sunlight breaks intodifferent colors.

Sunlight first refracts while entering the

water surface, then it is reflected back bythe mirror and once again refracts whileleaving the water surface. Separation ofcolors increases at all the three stages. Soyou get a clear break up of the sunlight intodifferent colours and see a sainbow.

In a prism also,light refracts twice, once

while entering and again while leaving theprism.

Experiment No. 6. Hole in palm:

Roll a paper sheet in to a tube andhold it in front of your righteye(touching the eye). Now, keep your left palm about 10cm. in front ofthe left eye(touching the tube).With right eye look through the tubeand with the left eye look straight atyour palm. Surprisingly, you see ahole in you palm and you are able tosee right through this hole.If you can’t see the hole, stare withboth the eyes for a few more seconds

and readjust the position of your palm.Even now if you do not get results,hold the tube in front of left eye andpalm in front of right eye.

One of the eyes sees the tube(holr) and the

other sees the palm. You brain blends boththe images and perceives them together.That’s why you see a hole in your palm.

Experiment No. 7. Fish in pot.

Draw a line in the center of the largecard. Draw a fish pot on one side ofthe line and a fish on the other.Hold the smaller card on the centerline, perpendicular to the picture card.Let the tip of your nose touch thesmaller card. Stare at the drawings.One eye sees the fish and the othersees the fish pot. Soon, the fishappears to be inside the fish pot. Ifyou don’t succeed at first, stare for alonger time.

One of your eyes sees the fish while the

other sees the pot. Your brain blends boththe images and perceives themsimultaneously.


MANY MORE ACTIVITIES:

Total internal reflection, Principle of fiber optics, water acts as mirror,disappearing picture, Rainbow in water drops, water prism.

Experiments :

Centre of gravity, Magnetism, energy, electricity, Laws of motions, Simple machines, pendulum, sound etc.

Education

Science experiments