Question

Classify each of the following changes as physical or chemical:

(a) condensation of steam

(b) burning of gasoline

(c) souring of milk

(d) dissolving of sugar in water

(e) melting of gold

Short answer

1. Physical
2. Chemical
3. Chemical
4. Physical
5. Physical

Step-by-step solution

Understanding what is physical and chemical change

Physical change is a type of change in which physical structure changes but chemical composition does not change.

Chemical change is a change in which chemical composition of a substance changes.

Analyzing the phenomenon (a), (b), (c), (d) and (e)

1. It can be reversed by evaporating,so it is a physical change.
2. It cannot be reversed, so it ischemical change.
3. Souring of milk cannot be reversed, so it is a chemical change.
4. Dissolving of sugar can be reversed using condensation and crystallization, so it isa physical change.
5. It can be reversed back on freezing, so it is a physical change.