Question

Which description explains events that take
place during the mixing? Select all that apply.

Warm water molecules move more
slowly than cold water molecules.

Collisions result in transfer of energy
from molecules of higher kinetic energy
to molecules of lower kinetic energy.

Warm water molecules slow down while
cold water molecules speed up.

Answer 1

Correct choices: the 2nd and the 3rd.

- "Collisions result in transfer of energy from molecules of higher kinetic energy to molecules of lower kinetic energy." — True. Energy is exchanged in collisions, on average flowing from faster (hotter) molecules to slower (cooler) ones.
- "Warm water molecules slow down while cold water molecules speed up." — True. As energy is transferred, hot molecules lose some kinetic energy and cold ones gain some until thermal equilibrium is reached.

The first statement is incorrect: warm water molecules move faster, not more slowly, than cold water molecules.