Answer:
:
Reaction to temperature:1 Mark
Examples: 2Marks
Metalsexpand on heating and contract on cooling. This expansion and contraction ofmetals isreversible.
Examples:
1) Small gaps are left between the rails that form the parallel lines of a railway track. These gaps are called expansion gaps. These gaps allow the rails to expand in hot weather. If there are no gaps or gaps are too small the lines can bend.
2) While making agricultural tools, the metal ring is heated before fixing the wooden handle. On heating, the metal ring expands. When the ring becomes bigger in size, the wooden handle can fix easily. When the metal ring cools, it contracts and the handle fits in tightly.The fixing of a metallic rim to the wooden base of the wheel of bullock cart can be done in a similar manner. The metallic rim used is slightly smaller in diameter than the wheels. On heating, the rim expandsand can easily lie on the wheels. When the rim cools, it contracts and presses tightly onto the wheels.