Question

Take three glass bottles with wide mouths. Label them A, B, and C. Fill about half of the bottle A with ordinary tap water. Fill bottle B with water which has been boiled for several minutes, to the same level as in A. In bottle C, take the same boiled water and of the same amount as in other bottles. In each bottle put a few similar iron nails so that they are completely under water. Add a teaspoonful of cooking oil to the water in bottle C so that it forms a film on its surface. Put the bottles away for a few days. Take out nails from each bottle and observe them. Explain your observations.

Answer 1

Observation and Explanation:

1. Bottle A (Tap Water):

   • Observation: The iron nails in bottle A will show signs of rusting.
   • Explanation: Tap water contains dissolved oxygen, which reacts with iron, causing rust formation.

2. Bottle B (Boiled Water):

   • Observation: The iron nails in bottle B will show little to no rust.
   • Explanation: Boiled water has reduced dissolved oxygen content, which slows down the rusting process.

3. Bottle C (Boiled Water with Oil):

   • Observation: The iron nails in bottle C will have no rust.
   • Explanation: The oil layer prevents any oxygen from entering the water, thereby preventing rusting.

Conclusion: Iron nail rust occurs due to the presence of dissolved oxygen in water. Boiling water reduces the oxygen content, and the oil layer prevents oxygen contact, thereby preventing rusting.