Final answer:
Thermometers are calibrated using the freezing and boiling points of water or a constant-volume gas thermometer, with the triple point of water serving as a reference for precision measurements.
Step-by-step explanation:
There are two common ways to calibrate a thermometer. The first method involves using the freezing point and boiling point of water at standard atmospheric pressure as reference points. The freezing point of water is 0°C or 32°F, and the boiling point is 100°C or 212°F. One would immerse the thermometer in a mixture of pure ice and water to calibrate the freezing point, adjusting the thermometer to read correctly at this temperature.
The second method involves using a constant-volume gas thermometer as a standard because its readings are highly accurate and reliable. It works by measuring the change in pressure of a gas at constant volume when subjected to temperature variations. The triple point of water, where the water is in equilibrium as a solid, liquid, and gas, is another reference point used in calibration, especially for more precise scientific measurements.