Question 6
(6) Nathan was investigating the rusting of iron. He set up five test tubes as shown below, and left them for three days.
| Test tube | Observation after three days |
| --- | --- |
| 1 | Nail slightly rusty |
| 2 | Nail still shiny |
| 3 | Nail still shiny |
| 4 | Nail very rusty |
| 5 | Nail slightly rusty, bubbles of gas seen |
(i) Explain why the nails had not rusted in Test tubes 2 and 3. [1 mark]
(ii) List down the required conditions for rusting to occur. [1 mark]
(iii) Explain how salt affects the rate of rusting. [1.5 marks]
(iv) Name the gas formed in Test tube 5? [1 mark]
(v) Suggest three ways to decrease the nail’s rate of rusting. [1.5 marks]
| Test tube | Observation after three days |
| --- | --- |
| 1 | Nail slightly rusty |
| 2 | Nail still shiny |
| 3 | Nail still shiny |
| 4 | Nail very rusty |
| 5 | Nail slightly rusty, bubbles of gas seen |
(i) Explain why the nails had not rusted in Test tubes 2 and 3. [1 mark]
(ii) List down the required conditions for rusting to occur. [1 mark]
(iii) Explain how salt affects the rate of rusting. [1.5 marks]
(iv) Name the gas formed in Test tube 5? [1 mark]
(v) Suggest three ways to decrease the nail’s rate of rusting. [1.5 marks]