According to the kinetic molecular theory, how does the molecular motion of a substance change when it transitions from the liquid phase to the gas phase?

• A. The molecules move slower and have less kinetic energy in the gas phase.
• B. The molecules move faster and have greater kinetic energy in the gas phase.
• C. The molecules move at the same speed in both phases.
• D. The molecules stop moving in the gas phase.

Answer: (B)

Verified step by step guidance

1. Recall that the kinetic molecular theory explains the behavior of particles in different states of matter based on their motion and energy.
2. Understand that in the liquid phase, molecules are close together but can move past each other, meaning they have moderate kinetic energy and speed.
3. Recognize that when a substance transitions from liquid to gas (vaporization), energy is absorbed, increasing the kinetic energy of the molecules.
4. Know that in the gas phase, molecules are far apart and move rapidly in random directions, which means their speed and kinetic energy are higher than in the liquid phase.
5. Conclude that the molecular motion increases in speed and kinetic energy when moving from liquid to gas, consistent with the correct answer.