Heat transfer by conduction in solids

Steps:

• Identify the heat transfer mode: vibration of molecules describes conduction, where heat passes through direct particle collisions without bulk motion.
• Classify materials: solids conduct heat mainly by molecular vibrations; fluids (liquids and gases) also involve convection when heated from below.
• Evaluate setup: heating from below promotes convection in fluids as warmer, less dense portions rise.
• Select material: only the solid lacks convection, relying solely on conduction.

Why C is correct:

• Rubber is a solid, so heat transfers entirely by conduction through lattice vibrations, per Fourier's law of conduction (q = -k ∇T).

Why the others are wrong:

• A. Air is a gas; convection dominates as hot air rises.
• B. Mercury is a liquid; convection occurs via density-driven flow.
• D. Water is a liquid; convection transfers heat upward through circulation.

Final answer: C