3RD TERM

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Experiment to demonstrate surface tension
Apparatus: Beaker, water, steel needle, filter paper and grease.
Procedure:
1. Apply the grease to the steel needle so that water will not wet it and place it on the filter paper
2. Carefully place it on the water surface

Observation:
The paper will absorb water and eventually sinks to the bottom of the beaker leaving behind the needle floating on the water provided the water is not disturbed. The water surface will also be depressed under the needle. The needle floats on the water surface due to surface tension.

Surface tension can be reduced by
1. Increasing the temperature of the liquid
2. Adding soap or detergent to the liquid
3. Adding alcohol
4. Adding camphor
Effects of surface tension
1. Ants and pond skaters are able to move on water surface because of surface tension
2. Small objects like razor blade and needle can be made to float on water when carefully placed as a result of surface tension
3. Mercury forms spherical droplets when spilled on glass because of surface tension
4. The hairs of a paint brush spread out and come together when dipped in clean water and removed respectively as a result of surface tension
5. water drops slowly from a loosely closed tap as a result of surface tension
6. the rise and depression of liquid in a narrow tube is as a result of surface tension



Experiment to demonstrate viscosity
Apparatus: beaker, two different liquids say, engine oil and kerosene
Procedure: pour the engine oil into the beaker and drop the ball bearing into it. Observe the ball bearing as it moves to the bottom of the beaker. Do the same thing using the other liquid (kerosene). You will observe that the ball bearing gets to the bottom of the beaker much earlier than it does in engine oil. Therefore viscosity in engine oil is higher than that in kerosene.