Chapter 17, Problem 90A

Interpretation Introduction

Interpretation: The reason why fusion is an endothermic process, but freezing is an exothermic process should be explained.

Concept Introduction : Endothermic process is one in which heat flows from the surroundings to the system, and the exothermic process is one in which heat flows from the system to the surroundings.

Explanation of Solution

Heat flows when there is a temperature difference between two bodies. It flows from the hotter body to the colder body.

In fusion, the solid gains heat while the surroundings cool down thus, it is an endothermic reaction whereas in freezing, the liquid loses heat and the surroundings warms up thus, it is an exothermic process.