A student investigated the temperature change when different masses of anhydrous ammonium nitrate were dissolved in 150 cm3150\text{ cm}^3150 cm3 of water.
Table 1 shows the student's results:
| Mass of ammonium nitrate added (g\text{g}g) | Lowest temperature of solution (∘C^\circ\text{C}∘C) |
|---|---|
| 3.0 | 17.6 |
| 6.0 | 14.8 |
| 9.0 | 12.0 |
| 12.0 | 9.2 |
| 15.0 | 6.4 |
Assuming a linear relationship, calculate the initial temperature of the water (the temperature where the mass of ammonium nitrate added is 0 g0\text{ g}0 g).
The student then repeated the experiment four times with 9.0 g9.0\text{ g}9.0 g of ammonium nitrate to check the reliability of the results. Table 2 shows these repeat trials:
| Trial 1 (∘C^\circ\text{C}∘C) | Trial 2 (∘C^\circ\text{C}∘C) | Trial 3 (∘C^\circ\text{C}∘C) | Trial 4 (∘C^\circ\text{C}∘C) |
|---|---|---|---|
| 11.8 | 12.3 | 11.9 | 12.4 |
Calculate the mean lowest temperature and express the result with its uncertainty in the form mean±uncertainty\text{mean} \pm \text{uncertainty}mean±uncertainty, where the uncertainty is calculated as half of the range.
53 exam-style questions on AQA GCSE Chemistry 3.1 Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations, covering 3.1.1 Conservation of mass and balanced chemical equations, 3.1.2 Relative formula mass, 3.1.3 Mass changes when a reactant or product is a gas, and 3.1.4 Chemical measurements. Each one has a worked solution and a mark scheme showing where the marks go.