Chapter 14, Problem 55A

Interpretation Introduction

Interpretation: The removal of heat energy from body on evaporation of alcohol from the person’s skin is to be explained.

Concept introduction: Reactions in which heat is absorbed are called endothermic reactions. We know that evaporation of alcohol is an endothermic process.

Answer to Problem 55A

The alcohol is a volatile liquid with weak intermolecular forces and a high vapor pressure. Particles of liquid are always moving and keep on evaporating in an open system.

Explanation of Solution

When a person has a severe fever and we have an alcoholic rub on a person’s body, the warm body provides heat energy and the particles of alcohol gain energy from the body and evaporates causing the person’s body to feel cool. In this way, evaporation of alcohol removes heat energy from the person’s body.

Conclusion

This is to conclude on the basis of property of liquid in an endothermic process.