Question

Classify the following processes into physical or chemical changes:

(i) The beating of aluminum metal to make aluminum foil.

(ii) Digestion of food.

(iii) Cutting of a log of wood into pieces.

(iv) Burning of crackers.

Answer 1

Physical changes:

1. The substance involved in a physical change is structurally identical before and after the change.
2. Texture, shape, temperature, and a change in the state of matter are examples of physical changes.

Chemical changes:

1. Chemical changes occur when a substance combines with another to form a new substance or alter a substance.

The beating of aluminium metal:

1. The process of converting metals into sheets is a non-chemical reaction and they can be reconverted into metals with some external conditions.
2. Hence, beating aluminum metal into aluminum foil is a physical change.

Digestion of food:

1. During digestion, food is broken down into smaller molecules with the help of the salivary glands present in the mouth.
2. This process involves the formation of a new substance. Therefore, it is a chemical change.

Cutting a log of wood:

1. Cutting a log gives pieces of wood that do not form a new substance.
2. Hence, cutting a log of wood into pieces is a physical change.

Burning of crackers:

1. The burning of crackers is a chemical change because it forms new products with different properties.
2. This chemical change also produces heat, light, and smoke.