The instrument that makes use of the fact that most liquids expand when they are heated is a thermometer.

Here's how it works:

* Liquid Expansion: Thermometers contain a liquid, typically mercury or alcohol, that expands as its temperature increases.

* Calibration: The thermometer is calibrated so that the expansion of the liquid corresponds to specific temperature readings.

* Measurement: As the liquid expands, it rises up a narrow tube, indicating the temperature.

Let me know if you have any other questions!