Question

Describe an activity to show that rusting of iron requires air and water

Answer 1

take some iron fillings(iron particles not rusted) in three test tubes and add some water in first test tube and then oil in it and in second test tube add some water and keep the third test tube dry(not even a drop of water in it). keep them at a safe place for few days and see what happens. 
you will observe that iron fillings in the second test tube get rusted and in the other test tubes it remains as it is.  This will prove rusting requires air and moisture