Describe an activity to find out the conditions under which iron can rust?

Iron rusts when exposed to moist air for a long time. The following activity explains the rusting of iron:

i. Take 3 test tubes and place clean iron nails in each of them. Mark them as A, B and C.

ii. Pour some water in test tube A and close the mouth of the test tube with a cork.

iii. Pour boiled water in test tube B and add a small amount of oil in it and cork it.

iv. Put some anhydrous calcium chloride in test tube C and cork it.

Observations: We will observe that in test tube A, iron nail got rust, but they do not rust in test tube B and C.

Explanation: In a test tube, the iron nail is exposed to air and water. In test tube B, the oil prevents the air from dissolving in water, and the nails are only exposed to water. In test tube C, anhydrous calcium chloride (drying agent) absorbs moisture in it. Hence the nails are only exposed to air.