Observation

Most of the candidates that attempted this question number did not give the required answers to the questions asked; consequently, the needed solutions to the entire question set are given below.

(a)

(i)  Annealing is a heat  treatment process in which metals are heated below their critical points and then allowed to cool in still air. The process reduces the internal stress of metals and increases their toughness.        
(ii) Hardening is a heat treatment process in which metals are heated above their critical points and then allowed to cool rapidly. The process increases the hardness of metals.

(b) Reasons why aluminium is used in auto body construction
- It is very light;
- It is durable;
- It is resistant to corrosion;
- It has a desirable colour;
- It has high thermal conductivity

(c) Constituents of bronze are copper and tin