How does a calorimeter record changes in temperature?

A calorimeter records changes in temperature primarily by detecting the heat exchange occurring during a physical or chemical process, often involving liquid and solid phases. The traditional way, particularly in classic calorimeters, involves a glass tube containing mercury, where the expansion or contraction of the mercury directly correlates to temperature changes. As temperature rises, the mercury expands and moves higher in the tube; when the temperature falls, the mercury contracts and moves lower. This movement provides a visual method to quantify changes in temperature based on the physical properties of mercury, which expands uniformly with temperature increases.

Modern calorimeters may enhance this principle by using digital sensors to provide more precise readings, but the fundamental mechanism, especially in traditional setups, relies on the observable change in a liquid's height, such as mercury, indicating temperature variations due to heat transfer during the reaction or process being studied.