In general, cooling causes the volume of most substances to decrease. This phenomenon is known as thermal contraction. It occurs due to the decrease in the average kinetic energy of particles as the temperature decreases. As particles move slower, they occupy less space, leading to a reduction in volume.

However, there are some exceptions to this rule. Notably, water exhibits an unusual behavior known as the 'density anomaly' or 'maximum density anomaly'. In the case of water, the density reaches its highest value at approximately 4°C (39.2°F). Below this temperature, the density of water decreases as it cools further, causing ice formed at 0°C (32°F) to float on liquid water.

In most other substances, the thermal contraction is a linear relationship. The rate of contraction per unit temperature change is known as the coefficient of thermal expansion (CTE). The CTE varies for different substances and is a fundamental property used to understand and design systems that undergo temperature changes.