Food Safety Certification Practice Test

How should you calibrate a thermometer using the ice point method?

1. Immerse the stem in boiling water

2. Immerse the stem in ice water

3. Place the thermometer in hot food

4. Submerge the thermometer in warm water

The correct answer is: Immerse the stem in ice water

The ice point method is a reliable technique used to calibrate a thermometer, ensuring it provides accurate readings, particularly at low temperatures. To perform the ice point calibration, you immerse the thermometer stem in a mixture of crushed ice and water. This combination creates a stable environment at approximately 32°F (0°C), the freezing point of water. When you submerge the thermometer in the ice water mixture, it's crucial to make sure that the stem does not touch the sides or bottom of the container, as that could give an inaccurate reading. After waiting for the reading to stabilize, adjust the thermometer to read 32°F (0°C) if it does not. This adjustment ensures that when you later use the thermometer for food safety purposes, it will provide accurate temperature readings. The other methods involve temperature points that do not apply specifically to the ice point calibration technique. Using boiling water would calibrate to the boiling point of water instead, which is not the focus of the ice point method. Placing the thermometer in hot food or warm water does not provide the same reference point, which is necessary for calibrating to the freezing point.