Mass change of iron nails after seven days0dry air0.06tap water0.19salt water Table 1 shows the mass of an iron nail before and after it was placed in three...
Question 1 Report
Table 1 shows the mass of an iron nail before and after it was placed in three different liquids for seven days. The nails were identical and were left uncovered in equal volumes of liquid. One liquid was tap water and another was salty water.
| liquid | mass change / g | appearance |
|---|---|---|
| dry air | 0.00 | no change |
| tap water | +0.06 | small rust patches |
| salt water | +0.19 | heavy rust coating |
(a) Use Table 1 to give the liquid that causes the fastest rusting. [1]
(b) Describe why the mass of a rusting nail increases. [1]
(c) Give one change that would make this investigation more reliable. [1]
Answer Details
(a) Salt water causes the fastest rusting. It gives the largest mass increase, \(+0.19\ \mathrm{g}\), and a heavy rust coating. [1]
(b) The nail gains mass because oxygen combines with iron. Oxygen atoms are added when rust forms. [1]
(c) Repeat each test using several identical nails in each liquid and calculate a mean mass change. This reduces the effect of anomalous results. [1]
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