How does an increase in thermal energy affect molecules?

How does an increase in thermal energy affect molecules?

• A. They stop moving
• B. They lose kinetic energy
• C. They decrease in temperature
• D. They begin to vibrate more

Answer: (D)

Increasing thermal energy raises the average kinetic energy of molecules, so they move more vigorously. In solids, this shows up as greater vibration about their fixed positions, while in liquids and gases it also means faster overall motion. That is why the correct statement is that they begin to vibrate more—adding heat makes microscopic motion more pronounced. The other ideas—stopping movement, losing kinetic energy, or cooling down—don’t occur when energy is added.

Increasing thermal energy raises the average kinetic energy of molecules, so they move more vigorously. In solids, this shows up as greater vibration about their fixed positions, while in liquids and gases it also means faster overall motion. That is why the correct statement is that they begin to vibrate more—adding heat makes microscopic motion more pronounced. The other ideas—stopping movement, losing kinetic energy, or cooling down—don’t occur when energy is added.