Thermal expansion enables temperature measurement

Steps:

• Liquid-in-glass thermometers rely on the expansion of liquid when heated.
• As temperature rises, the liquid's volume increases, causing it to rise in the narrow capillary tube.
• The height of the liquid column is calibrated to indicate temperature on a scale.
• This measurable change in volume directly corresponds to temperature variations.

Why D is correct:

• Volume expands with temperature per the thermal expansion law: ΔV = V₀ β ΔT, where β is the volume expansion coefficient, allowing precise temperature scaling.

Why the others are wrong:

• A: Thermometer length remains fixed as a structural feature.
• B: Liquid mass is conserved and does not vary with temperature.
• C: Specific heat capacity is a constant material property unrelated to expansion.

Final answer: D