Which statement best describes how fast-moving particles transfer thermal energy to a cup after hot tea is poured into it?

Which statement best describes how fast-moving particles transfer thermal energy to a cup after hot tea is poured into it?

• A. They collide with slow-moving particles.
• B. They replace slow-moving particles.
• C. They collide with other fast-moving particles.
• D. They are replaced by slow-moving particles.

Answer: (A)

Fast-moving particles transfer thermal energy to a cooler object mainly through collisions that randomize energy between the interacting molecules. In this case, the tea’s fast-moving molecules collide with the slower-moving molecules of the cup. Each collision can transfer some kinetic energy to the cup molecules, causing them to move faster on average and warming the cup, while the tea loses a bit of energy and cools. The key idea is energy is shared during collisions, not by replacing molecules or by collisions among fast-moving tea particles alone.

Fast-moving particles transfer thermal energy to a cooler object mainly through collisions that randomize energy between the interacting molecules. In this case, the tea’s fast-moving molecules collide with the slower-moving molecules of the cup. Each collision can transfer some kinetic energy to the cup molecules, causing them to move faster on average and warming the cup, while the tea loses a bit of energy and cools. The key idea is energy is shared during collisions, not by replacing molecules or by collisions among fast-moving tea particles alone.