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An Activity that demonstrates air and water exerts pressure.
 An Experiment which  relates that  air exerts pressure.

1.Aim:To show that air exerts pressure.
Materials required: Glass beaker, Index card.
Procedure:
 Take a 500 ml glass beaker and fill it with water. Cover the mouth of the beaker with an index card. Now, hold the card  tightly and invert the glass beaker along with water over the sink and remove your hand from the card. The card sticks to the glass.
Observation: Air exerts pressure on the card  from below to keep the card in tact.
Inference:This proves that the  pressure exerted by air upwards is more than the pressure exerted by water downwards. 

2.Experiment related to water exerts pressure.
Aim: To show that water exerts pressure.

Materials required:
Plastic bottle, glass tube,Burner, molten wax, thin rubber sheet.

Procedure:Take a plastic bottle. Fix a small glass tube a little above the bottom of the plastic bottle. Heat one end of the glass tube slightly over a burner and then insert the hot end immediately onto the outer surface of the plastic bottle. Seal the joint of the glass tube with plastic bottle by using molten wax so that water does not leak from the joint. Tie a thin sheet of rubber tightly on the open end of glass tube. Now, fill half of the plastic bottle with water.

Observation: On filling with water, the rubber sheet which is tied to the mouth of the glass tube gets stretched and bulges out. The bulging out of rubber sheet tied to the glass tube fixed in the outer surface of plastic bottle demonstrates that water present in plastic bottle exerts pressure on the wall of the bottle(or towards the side of the bottle). It is the sideways pressure exerted by water which inflates the thin rubber sheet forming a bulge. If we pour more water in the plastic bottle to increase its depth, we will see that the bulge in the rubber sheet increases. Inference: This indicates that the pressure exerted by water increases with increasing depth.
A liquid exerts pressure on the walls (or to the sides) of its container.


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