Measuring enthalpy changes of reactions
3 marks · EasyA student performs a calorimetry experiment to investigate the reaction between calcium chloride and water. Their thermometer readings at one-minute intervals are shown in the table below:
| Time (minutes) | Temperature (°C) |
|---|---|
| 0 | 21.0 |
| 1 | 23.1 |
| 2 | 24.8 |
| 3 | 24.5 |
| 4 | 24.1 |
State the highest temperature recorded during the experiment.
Calculate the temperature increase from 0 to the highest temperature.
Suggest why the temperature decreases after 2 minutes.
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.
Show answer
(a) 24.8 °C
(b) 3.8 °C
(c) Heat is lost to the surroundings.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies highest temperature (24.8 °C).
M1 (b) · 1 mark · Calculates temperature change: 24.8 – 21.0 = 3.8 °C. (follow-through)
B1 (c) · 1 mark · Gives valid reason (e.g., heat loss to surroundings, cooling after reaction).
Worked solution
a) The highest temperature is 24.8 °C.
b) Temperature increase is 24.8 – 21.0 = 3.8 °C.
c) The temperature decreases because heat is lost to the surroundings after the reaction finishes.