Final answer:
The statement is true; sweat evaporates from the skin in an endothermic process that cools the body, though this cooling effect is more efficient in lower humidity environments.
Step-by-step explanation:
The statement that when sweat evaporates, it cools the body because evaporation is an endothermic process is true. During evaporation, energy is absorbed from the skin to change liquid sweat into its gaseous form (water vapor), resulting in a cooling effect on the body. This process requires a substantial amount of energy because hydrogen bonds between water molecules need to be broken. The metabolic rate can affect the amount of sweat produced and, subsequently, the cooling effect.
Additionally, environmental conditions such as relative humidity have a significant impact on the evaporation rate. On hot, dry days, sweat evaporates more quickly, leading to more efficient cooling. Conversely, on humid days, the higher concentration of water in the atmosphere inhibits evaporation, making the body's natural cooling process less effective and leaving sweat unevaporated on the skin.
The cooling effect is essential for maintaining homeostasis of body temperature, which is vital for health and physical performance, especially during exercise or in hot weather.