How does an increase in thermal energy affect molecules?

• A. It increases the average kinetic energy of the molecules, causing them to move faster.
• B. It decreases the average kinetic energy of the molecules, causing them to move slower.
• C. It causes molecules to form chemical bonds spontaneously.
• D. It causes molecules to lose mass.

Answer: (A)

Verified step by step guidance

1. Understand that thermal energy is related to the energy associated with the motion of molecules in a substance.
2. Recall that the average kinetic energy of molecules is directly proportional to the temperature or thermal energy of the system.
3. Recognize that when thermal energy increases, the molecules gain more kinetic energy, which means they move faster on average.
4. Note that faster molecular motion can lead to changes in physical states (e.g., solid to liquid) but does not cause molecules to lose mass or spontaneously form chemical bonds.
5. Conclude that an increase in thermal energy increases the average kinetic energy of molecules, causing them to move faster.