According to the kinetic molecular theory, what happens to the molecules of a gas when the gas is heated?

• A. The molecules become larger in size.
• B. The molecules stop colliding with each other.
• C. The molecules slow down and their average kinetic energy decreases.
• D. The molecules move faster and their average kinetic energy increases.

Answer: (D)

Verified step by step guidance

1. Recall the kinetic molecular theory, which explains the behavior of gas molecules in terms of their motion and energy.
2. Understand that temperature is directly related to the average kinetic energy of gas molecules, where kinetic energy is given by the formula \(KE = \frac{1}{2}mv^2\), with \(m\) being mass and \(v\) velocity of a molecule.
3. When a gas is heated, the temperature increases, which means the average kinetic energy of the molecules increases as well.
4. As the average kinetic energy increases, the molecules move faster because their velocity increases.
5. Therefore, heating a gas causes its molecules to move faster and have higher average kinetic energy, not to become larger, stop colliding, or slow down.