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.