Question

Which of the following substances does not always expand on heating?

• A. Copper
• B. Water
• C. Oil
• D. Iron

Answer 1

The correct option is B Water

Generally, liquids expand on heating & contract on cooling.
However, water shows an exceptional behavior below $4{}^{\circ }\text{C}$.
If we cool water at room temperature we find that it goes on contracting, but as the temperature falls below $4{}^{\circ }\text{C}$ it begins to expand instead of contracting.
Conversely, if water is heated from $0{}^{\circ }\text{C}$ to $4{}^{\circ }\text{C}$ instead of expanding it contracts.