Chapter 3.2, Problem 12SSC

Interpretation Introduction

Interpretation:

The result of a chemical change and its four indicators needs to be explained.

Concept introduction:

In a chemical change, the new substance is formed. The composition of new substance is different from the original substance. The chemical change is irreversible.

Answer to Problem 12SSC

The formation of new substance and different ratio of elements are the resultant of a chemical change.

There are four indicators of a chemical change.

• Production of gas.
• Releasing energy or gain of energy.
• Color change.
• Formation of precipitation.

Explanation of Solution

A chemical property describes how a substance reacts with other substances. In a chemical change, a new substance is formed and absorption of energy or loss of energy occurs; it is an irreversible change. For example, rusting, dissolving, etc.

The main four indicators with example are as follows-

1. Production of gas (Sodium ignites when reacting with water, hydroxide is formed and hydrogen gas released.)
2. Releasing of energy or gain of energy (Burning of wood, is the example where the heat loss by the production of ash and gases)
3. Color change (The color changes when leaves fall).
4. Irreversible change (Iron rusting, when the iron reacts with moisture an oxide of iron is formed which cannot be converted into iron).

Conclusion

Required indicators are mentioned below:

1. Production of gas
2. Releasing of energy or gain of energy
3. Color change
4. Irreversible change