Describe an experiment to show that air exerts pressure in all directions. [3 marks]

Take a tin and boil some water in it. When steam begins to come out, cork it and stop heating it further. Put the tin in a trough and pour some cold water mixed with ice on it. [1 Mark]
You will observe that the tin gets crushed and becomes irregular in shape. [1 Mark]
This is because the cold water condensed the steam inside the tin to water. This left no air inside the tin. Thus, the pressure inside the tin became much lesser than that on the outside. The air pressure from outside acted on the tin from all directions and crushed it.
The above experiment shows that air exerts pressure in all directions. [1 Mark]