How would you calibrate a thermometer?

• A. Place the thermometer in a cup of ice water
• B. Place the thermometer in boiling water
• C. Compare with a standard thermometer
• D. Use a pressure gauge

Answer: (A)

Calibrating a thermometer means setting its readings against known, fixed reference points so the measurements are accurate. An ice-water bath provides a precise, reproducible point: at standard atmospheric pressure, a mixture of ice and water sits at 0°C. Placing the thermometer in that bath and adjusting it so it reads 0°C establishes the zero point of the scale. This gives you a trusted baseline from which other temperatures can be checked or adjusted if needed. Boiling-water checks can verify the high end, but pressure and practicality can affect that reading, so it’s not as universally reliable as the 0°C anchor. Comparing to a standard thermometer can help verify accuracy, but it doesn’t establish the zero point by itself. So, starting with an ice-water bath is the most straightforward and dependable way to calibrate.