Question

Describe with a labelled diagram an activity to investigate the conditions under which iron rusts.

Answer 1

Activity:

• Take three test tubes and label them as A, B and C.
• In each tube, place clean iron.
• Pour some water in te t tube A and cork it.
• Pour distilled water in test tube B, add about 1 ml of oil and cork it.
• Put some anhydrous calcium chloride in test tube C and cork it.
• Leave the test tube for few days.

Observation: Iron nail rusts in test tube A but they do not rust in test tubes B and C.

Explanation:

• It is because, in the test tube A, the nails are exposed to both air and water.
• In test tube B, the nails are exposed to only water because the oil prevents the air from dissolving in water.
• In test tube C, the nails are exposed to dry air because CaCl₂ will absorb the moisture from the air.

Conclusion: Air and water both are essential conditions for rusting.