Final answer:
The kinetic energy in matter decreases when it changes from a liquid to a solid due to reduced particle movement.
When matter changes from a liquid to a solid, the kinetic energy decreases. In a liquid, the particles have more freedom of movement and therefore higher kinetic energy. However, when the substance solidifies, the particles become more orderly and their movement becomes limited, resulting in a decrease in kinetic energy.
Step-by-step explanation:
When matter changes from a liquid to a solid, the kinetic energy in the matter decreases. This is because the particles in a solid vibrate less and have less free movement than in a liquid, indicating a reduction in kinetic energy. Hence, the correct answer to the question What happens to the kinetic energy in matter when it changes from a liquid to a solid? is B. Decreases.