How Does a Thermometer Work? | A2 ESL Science Reading Passage

Use this A2-B1 ESL science reading passage to learn how a thermometer works. It includes key vocabulary, reading comprehension questions, and answers for English learners.

A thermometer measures how hot or cold something is.

Reading Level

A2-B1

Word Count

192 words

Reading Passage

A thermometer is a tool that measures temperature. People use thermometers to check the weather, food, water, rooms, and science experiments.

Some thermometers have a thin glass tube with colored liquid inside. When the temperature rises, the liquid gets warmer. Warm liquid can expand, so it moves higher in the tube.

When the temperature falls, the liquid gets cooler. Cooler liquid takes up less space, so it moves lower in the tube. Numbers beside the tube show the temperature. A person reads the number where the top of the liquid stops.

Many modern thermometers are digital. A digital thermometer does not need a long glass tube. It uses a sensor to feel temperature. The sensor sends information to a small computer inside the thermometer. Then the number appears on a screen.

Thermometers are useful because temperature can change many things. Heat can melt ice, cook food, or change the weather. Cold can freeze water or keep food fresh.

Thermometers also help people compare temperatures. For example, a student can measure warm water and cold water in a science class. The numbers make the difference clear.

A thermometer helps people measure these changes instead of only guessing.

Thermometers measure temperature with expanding liquid or a sensor.

Key Vocabulary

Word	Meaning	Example
thermometer	a tool that measures temperature	The thermometer shows the room temperature.
temperature	how hot or cold something is	Temperature can rise during the day.
liquid	a substance that flows	Some thermometers use colored liquid.
expand	to get bigger or take up more space	Warm liquid can expand.
sensor	a part that detects or measures something	A digital thermometer uses a sensor.

Reading Comprehension Questions

1. What does a thermometer measure?
2. What happens to liquid when it gets warmer?
3. What happens to liquid when it gets cooler?
4. How does a person read a liquid thermometer?
5. What does a digital thermometer use to feel temperature?

Answers

1. A thermometer measures temperature.
2. The liquid expands and moves higher in the tube.
3. The liquid takes up less space and moves lower in the tube.
4. A person reads the number where the top of the liquid stops.
5. It uses a sensor.

Short Summary

A thermometer measures temperature by showing how heat changes liquid or by using a digital sensor.

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