What principle does a glass stem thermometer operate on?

A glass stem thermometer operates on the principle of expansion due to temperature. As the temperature of a substance increases, the liquid (usually mercury or colored alcohol) inside the glass tube expands and rises in the stem of the thermometer. Conversely, as the temperature decreases, the liquid contracts and the level falls. This expansion and contraction is a direct response to temperature changes, allowing the thermometer to provide a visual indication of the temperature on a calibrated scale. The glass stem acts as a protective container for the liquid, enabling accurate measurement without interference from external factors. The design and functionality of a glass stem thermometer exemplify this basic physical principle effectively, making it a common tool for temperature measurement in various applications.