Astronomy Practice Exam 2025 – Complete Preparation Guide

Temperature is defined as the average kinetic energy of particles within a substance. This concept is rooted in the kinetic theory of gases, which posits that the temperature of a substance is directly related to the motion of its particles. As the kinetic energy increases, particles move more vigorously, resulting in a higher temperature. Conversely, a decrease in kinetic energy corresponds to a lower temperature.

In essence, temperature serves as a measure of how energetic the particles are, impacting their behavior and the state of matter (solid, liquid, or gas). The other terms—pressure, volume, and matter—are related but denote different physical properties. Pressure relates to the force exerted by particles colliding with a surface, volume refers to the space occupied by a substance, and matter encompasses any substance that has mass and takes up space. Thus, temperature specifically quantifies the kinetic energy of particles, making it the correct answer to the question.