Chapter 2, Problem 59A

Interpretation Introduction

Interpretation: The given word equation needs to be used to explain the difference between a chemical and a physical change.

Concept Introduction: When a substance changes its appearance or change in the state takes place and there is no change in its chemical composition, the change is said to be physical. On the other hand, when there is a change in the chemical composition of a substance or a new substance is formed after a chemical reaction, it is known as a chemical change.

Explanation of Solution

The given word equation is as follows:

  $\text{iron}+\text{sulphur}\stackrel{\text{heat}}{\to }\text{iron sulfide}$

It shows the reaction between iron and sulfur to form iron sulfide. The reaction involves heating also, and a new substance is formed thus, it is a chemical change.

In a physical change, there is only a change in the appearance of a substance takes place. It does not affect the chemical composition of the substance. In the given equation, iron sulfide is formed from iron and sulfur. Here, iron and sulfur elements are combined in a fixed ratio by mass. If in any change heat is involved and a new substance is formed, it is considered a chemical change.