Thermal Expansion of Materials

Steps:

• Recall that most substances expand when heated due to increased kinetic energy of particles.
• Consider behavior of gases: at constant pressure, volume increases proportionally with temperature (Charles's law).
• Evaluate solids: linear and volumetric expansion occur in metals.
• Assess liquids: density changes lead to expansion, except for water's anomaly near 4°C.

Why A is correct:

• Gases expand at constant pressure because Charles's law states V ∝ T, so rising temperature increases volume to maintain pressure.

Why the others are wrong:

• B: Metals expand in both length and volume, not just length.
• C: Most liquids expand with temperature; water contracts only between 0°C and 4°C before expanding.
• D: The hole in a metal disc expands as the surrounding metal expands, equivalent to adding material.

Final answer: A