In what scenario does thermal expansion occur?

Thermal expansion occurs when the temperature of a material rises. As temperature increases, the kinetic energy of the particles increases, causing them to move more vigorously and generally occupy more space. This increase in particle movement leads to an increase in the distance between particles, resulting in the material expanding.

In solids, this means that the structure becomes larger as the atoms or molecules move apart. In liquids and gases, the same principle applies, although the effects may be more pronounced due to the larger amount of space between particles in these states of matter. Understanding thermal expansion is crucial in many scientific and engineering applications, such as construction, where materials expand and contract with temperature changes.

In contrast, when a gas is compressed, the volume decreases as particles are pushed closer together, which is the opposite of expansion. The cooling of solids leads to contraction rather than expansion, and dissolving a mass of liquid does not inherently change the temperature of the material involved, thus it does not contribute to thermal expansion in that context.