Table 1 shows the temperatures in a self-cooling drinks can. The can has a separate compartment of water and a solid salt. Fig. 1 shows the compartments bef...
Question 1 Report
Table 1 shows the temperatures in a self-cooling drinks can. The can has a separate compartment of water and a solid salt. Fig. 1 shows the compartments before the base is twisted.
| time after twisting / min | drink temperature / degrees C |
|---|---|
| 0 | 24 |
| 3 | 16 |
| 8 | 15 |
(a) Use Table 1 to calculate the total temperature decrease. [1]
(b) Name the direction of energy transfer during dissolving. [1]
(c) Explain why the drink compartment becomes cooler. [2]
A technician prepared a cold pack for a sports clinic by dissolving ammonium nitrate in water. Fig. 1 shows the pack being squeezed so that the water enters the compartment containing the solid. Table 1 shows the result.
| time / min | temperature / degrees C |
|---|---|
| 0 | 22 |
| 2 | 13 |
| 5 | 12 |
(a) Use Table 1 to calculate the decrease in temperature. [1]
(b) Name this energy-change type. [1]
(c) Explain why the pack can be used on a minor injury. [2]
Answer Details
Both contexts involve endothermic dissolving, in which the dissolving mixture absorbs energy from its surroundings.
- Self-cooling can (a) \[24 - 15 = 9\ ^\circ\mathrm{C}\] The total temperature decrease is \(9\ ^\circ\mathrm{C}\). [1]
- Self-cooling can (b) Energy transfers from the drink, or its surroundings, to the dissolving salt mixture. [1]
- Self-cooling can (c) Dissolving is endothermic, so it absorbs energy. Energy is taken from the drink through the can wall, making the drink cooler. [2]
- Cold pack (a) \[22 - 12 = 10\ ^\circ\mathrm{C}\] The temperature decreases by \(10\ ^\circ\mathrm{C}\). [1]
- Cold pack (b) This is an endothermic energy change. [1]
- Cold pack (c) Dissolving absorbs thermal energy from the surroundings. The pack becomes cold and can cool the injured area. [2]
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