What is the correct method for calibrating a thermometer?

Calibrating a thermometer is typically done to ensure its accuracy in measuring temperature. The most widely accepted method for calibrating a thermometer is to use the freezing point of water, which is commonly achieved by placing the thermometer in a mixture of ice and water. This method is reliable because the melting point of ice at standard atmospheric pressure is 0 degrees Celsius (32 degrees Fahrenheit).

By using ice water, the thermometer can be set to read 0 degrees Celsius to confirm its accuracy. If the thermometer does not display this value, it may require adjustment or recalibration to ensure precise readings in practical applications. This method is favored due to its simplicity and consistency under normal atmospheric conditions.

The other suggested methods lack the precise reference point provided by the ice water mixture. Boiling water is also used for calibration, typically for thermometers measuring higher temperatures. However, it has some limitations due to variations in atmospheric pressure and boiling point depending on location. Warm air and room temperature water do not provide reliable benchmarks for calibration, making them less suitable for accurate thermometer calibration.