Conditions are - air and moisture.
Activity: Take three test-tubes. Place clean iron nails in each test-tube.
(i) Pour some water in test-tube 1, cork it.
(ii) Pour water (boiled/distilled) in test-tube 2, add some oil and cork it.
(iii) Put some anhydrous calcium chloride in test-tube 3 and cork it.
(iv) After 2-3 days, we observe that the nails in test-tube 1 get rusted because they are exposed to air and water both, while nail in test-tube 2 and 3 do not get rusted. This shows rusting of iron takes place in the presence of air and moisture, both.
Methods to prevent rusting: Alloying, galvanization, painting, lubrication.
