Which metal is a liquid at room temperature and, because it contracts and expands, can be used to measure temperature?

What the clue is pointing to

The question describes a metal that is liquid at room temperature and changes volume predictably with temperature. That is exactly the property needed for a liquid-in-glass thermometer.

Matching the description to a metal

• Most metals are solid at room temperature.
• Mercury is unusual because it is a metal that remains liquid at room temperature.
• Mercury’s volume increases when temperature rises and decreases when temperature falls.

Why it works in thermometers

In a glass thermometer, a column of mercury moves up or down a narrow tube as its volume changes. That movement can be calibrated to show the temperature.