When the temperature of a substance increases, what happens to the molecules within it?

• A. The molecules move slower and have less kinetic energy.
• B. The molecules stop moving completely.
• C. The molecules move faster and have greater kinetic energy.
• D. The molecules decrease in size.

Answer: (C)

Verified step by step guidance

1. Understand that temperature is a measure of the average kinetic energy of the molecules in a substance.
2. Recall that kinetic energy of molecules is related to their motion; as temperature increases, molecules gain energy.
3. Recognize that when molecules gain kinetic energy, they move faster, increasing their speed and frequency of collisions.
4. Note that molecules do not stop moving completely at higher temperatures; in fact, they move more vigorously.
5. Understand that molecules do not change in size due to temperature changes; size is determined by molecular structure, not temperature.