Evaporating sweat cools the body because evaporation is an...

Evaporating sweat cools the body because evaporation is an endothermic process: $$ \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{O}(g) \quad \Delta H_{\mathrm{ren}}^{\mathrm{e}}=+44.01 \mathrm{kJ} $$ Estimate the mass of water that must evaporate from the skin to cool the body by $0.50^{\circ} \mathrm{C}$ . Assume a body mass of 95 $\mathrm{kg}$ and assume that the specific heat capacity of the body is 4.0 $\mathrm{J} / \mathrm{g} \cdot^{\circ} \mathrm{C}$ .

Evaporating sweat cools the body because evaporation is an endothermic process:
$$
\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{O}(g) \quad \Delta H_{\mathrm{ren}}^{\mathrm{e}}=+44.01 \mathrm{kJ}
$$
Estimate the mass of water that must evaporate from the skin to cool the body by $0.50^{\circ} \mathrm{C}$ . Assume a body mass of 95 $\mathrm{kg}$ and assume that the specific heat capacity of the body is 4.0 $\mathrm{J} / \mathrm{g} \cdot^{\circ} \mathrm{C}$ .

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Key Concepts

Specific Heat Capacity

This concept refers to the amount of heat energy required to raise the temperature of a unit mass of a substance by one degree Celsius. In thermal calculations, it is used to determine the total energy change needed to raise or lower an object’s temperature, and it directly connects the mass of an object, its temperature change, and the heat energy involved in the process.

Latent Heat of Vaporization

Latent heat of vaporization is the energy required per unit mass to change a substance from a liquid to a gas at constant temperature. This property is significant in cooling processes because when a liquid evaporates, it absorbs a substantial amount of energy from its surroundings, thereby producing a cooling effect.

Energy Conservation in Heat Transfer

This principle involves balancing the energy lost or gained by a system with the energy absorbed or released by another process. In a thermal cooling system, the energy removed from a body (calculated through its specific heat capacity and temperature change) is equated to the energy absorbed by an endothermic phase change process, such as evaporation, ensuring the overall conservation of energy during the process.

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