Explanation
(a) Heat capacity is the quantity of heat required to change the temperature of a body by 1K. The unit is JK\(^{-1}\)
(b) Effects of heat on a substance are:
(i) Increase in temperature.
(ii) Change of state.
(iii) Change in colour .
(iv) Change in electrical resistance, etc.
(c) To remove a tightly fitted glass cork from a reagent bottle, warm the bottle neck using warm cloth to make the glass bottle to expand creating space for easy removal of the cork.
(d)(i) Pt = MC\(\Delta \theta\)
\(\Delta \theta = \frac{pt}{Mc} = \frac{1200 \times 3 \times 60}{0.8 \times 4000}\) =67.5°
= final temp \(\theta\) = 67.5 + 30° = 97.5°C

(ii) Containers with tight-fitted lids are not suitable because with increase in temperature the steam molecules from the container are confined in the container, thereby increasing the rate of collission of the steam with the walls of the container, hence in pressure inside the container. Thus the high pressure can burst the tightly-fitted container and the hot content released.
(iii) The observed dent on the container is due to the condensation of the steam in the container which-will lead to a decrease in pressure in the greater container making the atmospheric pressure greater than the pressure in the container.

