OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What condition is required for sweating to effectively cool the body?

1. High humidity

2. Low air circulation

3. Rapid evaporation of sweat

4. Cold temperatures

The correct answer is: Rapid evaporation of sweat

Sweating effectively cools the body through the mechanism of evaporation. When sweat evaporates from the surface of the skin, it absorbs heat from the body, resulting in a cooling effect. For this process to occur effectively, rapid evaporation of sweat is essential. In conditions of high humidity, the air is already saturated with moisture, which slows down the evaporation process. Low air circulation can also impede evaporation, as stagnant air prevents the movement of moisture away from the skin. Conversely, cold temperatures may reduce the need for sweating altogether, as the body does not require additional cooling in cooler environments. Therefore, the optimal condition for sweating to cool the body is rapid evaporation of sweat, which facilitates the most effective transfer of heat away from the skin.