Question

Determine whether each of the following change is physical or chemical. Give reason for your answer. (i) A balloon filled with hydrogen gas explodes upon contact with the spark. (ii) Copper turns green on exposure to air and water. (iii) A metal surface becomes dull because of continued abrasion.

Answer 1

In (i), the explosion of a balloon filled with hydrogen gas upon contact with a spark is a chemical change. In (ii), the green coloration of copper on exposure to air and water is also a chemical change. In (iii), the dulling of a metal surface due to continued abrasion is a physical change.

Step-by-step explanation:

(i) The explosion of a balloon filled with hydrogen gas upon contact with a spark is a chemical change. This is because the hydrogen gas reacts with the spark to produce a new substance, such as water vapor. The original hydrogen gas is no longer present.

(ii) The green coloration of copper on exposure to air and water is a chemical change. It is due to the formation of copper(II) oxide and copper(II) hydroxide on the surface of copper. These new substances give copper its greenish color.

(iii) The dulling of a metal surface due to continued abrasion is a physical change. This is because the metal surface is only being physically damaged or scratched, but no new substances are formed.

Learn more about Physical and Chemical Changes