Explain how the properties of water are important during sweating as a mechanism for cooling the human body.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
When the human body overheats, sweat glands produce sweat, which is released onto the skin surface. As sweat evaporates, the body temperature falls.
Model answer (5 marks)
1. Water has a high specific heat capacity, so it can absorb a large amount of heat before its temperature rises.
2. This property prevents the body temperature from increasing rapidly during exertion.
3. Water also has a high latent heat of evaporation, meaning a large amount of energy is required to change it from liquid to vapour.
4. When sweat evaporates from the skin, it takes this heat energy away, cooling the body.
5. Because water is an excellent solvent, sweat can dissolve and carry waste solutes such as urea and ions out of the body.
2. This property prevents the body temperature from increasing rapidly during exertion.
3. Water also has a high latent heat of evaporation, meaning a large amount of energy is required to change it from liquid to vapour.
4. When sweat evaporates from the skin, it takes this heat energy away, cooling the body.
5. Because water is an excellent solvent, sweat can dissolve and carry waste solutes such as urea and ions out of the body.
Examiner tips
- Use the exact terms ‘specific heat capacity’ and ‘latent heat of evaporation’.
- Show the causal link: high heat capacity → stable temperature; high latent heat → heat removal by evaporation.
- Mention waste removal to cover all scheme points.
Common mistakes
- Confusing specific heat with latent heat; they are distinct properties.
- Omitting the role of sweat as a solvent for waste products.
Mark scheme (5 marks)
- Water has a high specific heat capacity / requires a large amount of energy to change temperature
- This helps prevent the body temperature from rising too rapidly / helps maintain a stable internal temperature
- Water has a high latent heat of evaporation / a large amount of energy is needed to evaporate water
- When sweat evaporates, it takes a large amount of heat energy away from the skin / body
- Water is a good solvent, so sweat can carry dissolved waste / solutes (e.g. urea, ions) out of the body
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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