Preventing rusting by galvanising
3 marks · EasyThe table below shows the results of an experiment. Three identical iron nails were placed under different conditions for 10 days to investigate rusting.
| Test tube | Conditions | Rust formed after 10 days? |
|---|---|---|
| 1 | Air only | No |
| 2 | Water only (boiled, air excluded) | No |
| 3 | Air and water | Yes |
Which test tube shows the conditions needed for rusting?
Explain why no rust formed in test tube 2.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Test tube 3
(b) No rust formed because although water was present, there was no air/oxygen.
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Marking points
B1 (a) · 1 mark · Test tube 3 identified as showing rust formation/necessary conditions.
B2 (b) · 1 mark · States that air or oxygen was excluded (boiled water, air absent).
B3 (b) · 1 mark · States both water and oxygen are needed for rusting; only water is present in test tube 2.
Worked solution
a) Test tube 3 shows the conditions needed for rusting because rust only forms where both air and water are present.
b) No rust forms in test tube 2 because air (or oxygen) has been excluded, even though water is present. Both air and water are needed for rusting.