Write an experiment to show that air exerts pressure in all directions

Experiment: Submit a can or plastic bottle with hot, sealed air to a sudden cooling and watch what happens.

Explanation:

Air is a mixture of gases (mainly oxygen and nitrogen, but also carbon dioxide, water vapor, and others in minimum amount).

The pressure of the gases is the product of the collisions of the air molecules with the surface of the objects. Since the molecules of gases are in constant, rapid random motion, they are constantly (you may say continously) colliding with the surfaces of the objects in all directions. That explain, why the air exertes pressure in all directions.

There are many experiments that you can perform to show this phenomenum.

You can perform this experiment, for example:

Take an "empty" can or plastic bottle, which you can heat using a source of hot water. You can do this by introducing the can or plastic bottle inside a pan with hot water, avoiding that the water enters into the your object.

Once the air inside the can or plastic bottle is hot, remove it from the pan and close it, so that air cannot exit from of enter into it.

Pour cold water over the can or plastic.

What will you observe?

The can or plastic bottle will collapse.

Why does that happen?

Because, when you pour cold water over the can or plastic bottle the air inside will cool down, and as result the air inside it will exert less pressure over the inner walls than the pressure that the air ouside it exerts over the outer walls.

Since the pressure is exerted in all the directions, the bottle or can collapse.