Question

Which of the following are physical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal

• A. (i), (ii) and (iii)
• B. (i), (ii) and (iv)
  
• C. (ii), (iii) and (iv)
• D. (i), (iii) and (iv)

Answer 1

The correct option is D

(i), (iii) and (iv)

1. Physical change is a type of change in which only the physical properties of the substance like colour, size, shape, etc, change but no new substance is formed. Example: Conversion of water into steam.
2. Chemical changes are irreversible and a new product is formed. Example: Digestion of food.

An explanation for correct option:

Melting of iron:

1. When iron is melted only the state of iron changes.
2. The solid iron changes its state of matter as solid turns liquid.
3. Thus, it's a physical change.

Bending of iron rod:

1. When we bend the iron rod, only the shape of the rod changes, and no new substance is formed.
2. It's a physical change.

Drawing a wire of iron metal

1. Since iron is a metal it will possess the property of ductility. Hence, a wire can be formed.
2. This does not change the composition of the metal, it only changes its shape.
3. Hence, it's a physical change.

Since melting of iron, bending of iron rod, and drawing a wire of iron metal are physical changes thus option (d) is the correct option.

An explanation for incorrect options:

Rusting of iron:

1. When the iron is exposed to air and moisture, rust formation takes place.
2. Rust is nothing but Iron Oxide; a new substance formed out of the reaction.
3. Brown flaky material is formed on the surface of iron when the iron is exposed to moist air thus it's also a chemical change.

Since rusting of iron is a physical change thus options (a), (b), and (c) are incorrect.

Hence, option (d) is the correct option.