Heat Transfer by Conduction

Steps:

• Hot solid's molecules vibrate faster due to higher kinetic energy.
• When solids touch, vibrations transfer directly to adjacent molecules in the cold solid.
• This molecular energy transfer continues until thermal equilibrium is reached.
• The process explains why heat flows from hot to cold without bulk movement.

Why B is correct:

• Conduction is the transfer of thermal energy through direct molecular collisions, as defined in the kinetic theory of matter.

Why the others are wrong:

• A: Expansion affects volume but does not cause energy flow between solids.
• C: Heat rises only in convection with fluids, not conduction in solids.
• D: Molecules in solids vibrate in fixed positions, not move randomly.

Final answer: B