Science experiments.

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IMPORTANCE OF HANDS-ON ACTIVITY:
Science has become an integral part of human life. Application of science has provided
many benefits, and a better Quality of life. The world today uses a language which has a lot of
science in it.
Without knowing, we use many words and phrases derived from science. We are also
becoming conscious of our environment as well as our economy. Science has much to do with
both these aspects, not only children but adults alike have to know the principles of science and
must be able to use the language of science where necessary. They must be able to apply the
lessons 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 and
result is that all the student who undergone through activity they understood the basic
knowledge. 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 own
with very little help from teachers. Learning is expected to be activity centered with the learners
doing experiments.
So let us starts some Hands-on activities:
AIR AROUND US
The ancient Greek philosophers were sure that air contained only one substance and
called it an element. Indian Philosophers also has the same idea and called it Vayu. But
everyone agreed that the air around us was like an invisible ocean enveloping both the seas and
the 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,
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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 facing
forward. With the other hand, press a paper
sheet on this palm, the paper falls down as
soon as you release it. Again press the paper
sheet. But this time begin to run fast palm
facing 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 paper
against 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 them
from the same height. They fall with
more or less the same speed.
 Now crumple one or them into a ball.
Again release a sheet and the ball
from the height.
 When the sheet falls, it pushes the air
below it and it turn air also pushes it
up. 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 count
the number of breaths required to fill
the bag. Try several times. Ask your
friends also and count the number of
breaths.
 Now hold the opening about 15 cm.
away from your mouth and blow hard
and long into the bag. Surprisingly,
the bag gets filled with air, with just
one 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 bendy
straw. Still blowing put a ping-pong
ball over the shown in the picture.
The ball gets trapped in the air stream
and hovers in midair.
2. – Hold a paper strip (20cm*4cm) just
below 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 strip
lowers down and air below the strip pushes
it up.
3. – Make a hole in the middle of a small
PVC pipe. Hold the pipe such that the
hole is about 1cm from a candle flame.-
Blow steadily through the pipe; the flame
is pulled towards the hole.
Experiment No. 5. Vacuum lift.
Fill the large test tube three-fourths
with water push the smaller test tube
halfway in it.
Keep holding the outer test tube and
invert the setup. As water starts
coming out through the clearance
between the two test tubes, the
smaller test tube rises up.
 Water falls down through a very narrow
clearance between the test tubes leaving no
space for air to enter. This creates a low-
pressure area inside the large test tube. The
atmospheric air, which is at a higher pressure,
forces the inner test tube up.
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HEAT
To keep your body warm during winter
you usually rub your palm. When you
exercise vigorously your body gets warmer.
So in ancient times people produced heat by
rubbing two stones or wooden pieces which
led to the invention of fore. Heat is a form of
energy.
Experiment No. 1. See Heat Flows!
Leaving 6-7 cm from one end of the
spoke drop 4-5 drops of molten wax
at an interval of about 1cm. Press the
heads of 4-5 nails in to the wax to fix
them. Take precaution, molten wax
may burn you hands.
Hold one end of the spoke to candle
flame. Soon, the nail nearest to the
flame 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 pass
on heat to neighboring particles. This
process continues until the entire object gets
equally hot. This mode of transfer of heat is
called ‘conduction’.
Experiment No. 2. Thread does not
burn:
Tightly wrap 20-25 turns of thread
around the screwdriver’s metal part
such that each turn makes good
contact with the rod.
Hold the threaded part over a flame
for 4-5 minutes. Unwrap and see; the
thread has not burnt.
 Iron is good conductor of heat. As thread
starts getting hot, its heat is conducted to
iron. As no time the thread gets hot enough
to burn.
Wrap the thread around a wooden rod and see
whether the thread burns.
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Experiment No. 3. Paper dose not
burn.
Wrap a piece of paper tightly around a
coin. Hold it with pliers over a flame.
See how long the paper takes to burn.
Explanation as same as the above
experiment.
Experiment No. 4 : Heat Water in paper
cup
Make a small paper cup using pins. It
should hold water without leaking.
Fill half of this cup with water and
hold it over a candle flame. Take care
not to burn your fingers. To your
surprise water gets hot but the paper
cup doesn’t burn.
 Water absorbs most of the heat and
prevents the temperature of the paper cup
to 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 from
the paper and rise up. Other cooler
molecules take their place. They also absorb
heat and go up. This process continues and
prevents the paper cup from becoming too
hot.
 Second property of water is its high specific
heat. Due to high specific heat, even after
absorbing much heat rise in its temperature
is small. Specific heat of a substance is the
amount of heat needed to raise the
temperature of a gram of the substance by
10
c.
Experiment No. 5.Fire proof
balloon.
Bring a light match near an inflated
balloon. It burnsts, even before the
flame touches it.
Now hold a water filled balloon over
a candle flame (flame should touch
only the portion dontaining
water).Does the balloon burst? See
for how long water can be heated.
 When there’s no water inside the balloon,
the rubber of the balloon gets hot instantly
and melts.
 When the rubber of water filled balloon
begins to heat up, it starts transferring heat
to the water. This heat is dispersed
throughout the volume of water. So the
rubber coesn’t get hot enough to melt.
Experiment No. 6. Convection
currents.
Cut a hole of about one square cm
near one end of the pipe. Put the pipe
over a lighted candle, with hole at the
bottom. Hold some lighted agarbattis
near the hole. Smoke is sucked into
the 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 hole
to take its place. In turn, this air also gets
heated, rises up. Thus an sir current is set
up 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 carbon
dioxide and would go out due to lack of
oxygen.
 In liquids too, heat is transmitted by
‘convection’.
Experiment No. 7. Heat Expands
wire.
Bend the spoke in a V-shape. Pull both
ends a bit closer and fasten the copper
wire taut between them. Rest a
piece of refill should be placed such
that is dislodges with the slightest
increase in the gap.
Heat the wire. Within a couple of
minutes, the wire expands and the
refill falls.
 Molecules(or atom) of all substances are
in vibratory motion all the while. Even
while vibrating, the molecules of solids
maintain their mean position. When
heated, the molecules become more
energetic and require more space to
vibrate. This results is expansion.
 Rails get heated due to friction and in
summer also. So gaps are left between
their joints.
VISION :
Experiment No.1. Coin disappears.
Place a coin in a bowl of water. Put an
inverted glass over the coin; it disappears.
 When light passes from a rarer (air) to a
denser (water) medium it bends towards the
normal 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 to
reach your eyes.
 The coin disappeared, but ha a void been
created there? Perform once again and
observe carefully. This question is discussed
in the experiment “Disappearing picture”.
Experiment No 2.Coin appears
again.
Place the coin in the bowl. Place yourself,
from where you can see just the far edge of
the coin. Move back yourself slightly; the
edge of the bowl hides the coin. Now your
friend 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 gets
refracted. As a result, the rays that were
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earlier going above your eye level now bend
down and reach your eyes. This makes the
coin 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. The
fish is actually slightly lower than its image.
 When you first see the rising sun, it is
actually below the horizon. Earth’s
atmosphere refracts the sunlight and we see
the sun earlier.
Experiment No. 3. Total internal
reflection.
To make light beam visible, add a few
drops of milk in half a cup of water.
From the side of the cup, point the
laser beam up, at the water surface.
By increasing the angle of incidence,
you may arrive at an angle when the
beam reflects back into water.
 The angle of incidence at which the
refracted beam is along the interface is
called the ‘critical angle’. Beyond this
angle, light is reflected back into water.
This Phenomenon is called ‘total internal
reflection’.
Experiment No. 4. Principle of fiber
optics.
Punch a hole near the bottom of the
bottle. In a dimly lit room, point the
laser beam at the hole. Add a few
drops of milk in water and pour it in
the bottle. The light now travels along
the water stream. Put a finger in the
stream, and see a spot of light on you
finger.
 In the water stream, light strikes the
interface between water and outside air at
an angle more than the critical angle. So it
is reflected back into the stream itself. This
reflected beam too strikes the opposite
surface at an angle more than the critical
angle and is again reflected back. This
process 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 you
direct a beam of light into the tube, it
repeatedly gets reflected until it reaches the
other end. This would work, even if the
tube were bent. The same thing happens in
the case of the water stream.
Experiment No. 5. Water prism.
Cover the windows with dark paper,
leaving space for just a streak of
sunlight to enter the room.
Place the mirror ina slanting position
in a bowl full of water. Position bowl
to get a reflection of sunlight on a
wall. Adjust them properly; you get a
beautiful rainbow on the wall.
 Sunlight comprises many colors. While
refracting, different colors bend at different
angles. Red bends the least and violet bends
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the most. Hence sunlight breaks into
different colors.
 Sunlight first refracts while entering the
water surface, then it is reflected back by
the mirror and once again refracts while
leaving the water surface. Separation of
colors increases at all the three stages. So
you get a clear break up of the sunlight into
different colours and see a sainbow.
 In a prism also,light refracts twice, once
while entering and again while leaving the
prism.
Experiment No. 6. Hole in palm:
Roll a paper sheet in to a tube and
hold it in front of your right
eye(touching the eye). Now, keep
your left palm about 10cm. in front of
the left eye(touching the tube).
With right eye look through the tube
and with the left eye look straight at
your palm. Surprisingly, you see a
hole in you palm and you are able to
see right through this hole.
If you can’t see the hole, stare with
both 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 and
palm in front of right eye.
 One of the eyes sees the tube(holr) and the
other sees the palm. You brain blends both
the 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 large
card. Draw a fish pot on one side of
the line and a fish on the other.
Hold the smaller card on the center
line, perpendicular to the picture card.
Let the tip of your nose touch the
smaller card. Stare at the drawings.
One eye sees the fish and the other
sees the fish pot. Soon, the fish
appears to be inside the fish pot. If
you don’t succeed at first, stare for a
longer time.
 One of your eyes sees the fish while the
other sees the pot. Your brain blends both
the images and perceives them
simultaneously.
BIJAPUR -586103

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.

Science experiments.

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Science experiments.