Question

which statement best describes the direction of heat flow by conduction between two samples of the same material?
○ heat flows from faster molecules to slower molecules when they are near.
○ heat flows from faster molecules to slower molecules when they collide.
○ heat flows from slower molecules to faster molecules when they are near.
○ heat flows from slower molecules to faster molecules when they collide.

Explanation:

To determine the correct statement about heat flow by conduction, we recall the concept of thermal energy transfer. Heat transfer by conduction occurs due to molecular collisions. Faster - moving (higher - kinetic - energy) molecules transfer energy to slower - moving (lower - kinetic - energy) molecules during collisions.

• Option 1: Heat transfer in conduction requires collisions, not just being near. So, this is incorrect.
• Option 2: When faster - moving molecules collide with slower - moving ones, they transfer energy (heat), which aligns with the principle of conduction.
• Option 3: Heat flows from higher - energy (faster) to lower - energy (slower) molecules, not the other way around, and also requires collisions, not just being near. So, this is incorrect.
• Option 4: Heat flows from faster to slower molecules, not slower to faster. So, this is incorrect.

Answer:

B. Heat flows from faster molecules to slower molecules when they collide.