How does thermal expansion impact liquid levels in thermometers?

Thermal expansion affects liquid levels in thermometers because the liquid inside (usually mercury or colored alcohol) expands or contracts as the temperature changes.

Here’s how it works:

1. Heating the liquid: When the temperature rises, the liquid molecules gain energy and move more vigorously, causing the liquid to expand in volume.
2. Rising level: Since the liquid is contained in a narrow, sealed glass tube, the expanding liquid has nowhere to go but up the tube, causing the liquid level to rise.
3. Cooling the liquid: When the temperature drops, the liquid contracts, taking up less volume, and the level in the tube falls accordingly.