What is a Thermometer?

A thermometer is an instrument we can use to measure temperature. An analog thermometer consists of a sealed tube with markings on it. These markings are increasing temperatures in Celsius or Fahrenheit. The markings on a clinical and weather thermometer are different, but they work in the same way.

How does a Thermometer Work?

The glass tube of a thermometer usually contains mercury. Mercury is perfect to test temperature because it changes from a solid to liquid very easily.

When the metal tip of the thermometer comes into contact with the material it is testing, it conducts heat energy to the mercury. The mercury turns into liquid and so it expands. It begins to rise up the tube. Where it stops, is where you can take the temperature reading on the scale.

How does a Digital Thermometer Work?

Digital thermometers are different because they use a computer chip to tell the temperature instead of mercury. You would normally have to wait three whole minutes for the mercury to heat up and give you a reading.

It takes only 30 seconds for a digital thermometer to give you a reading because the heat-sensitive tip is able to accurately tell the computer chip inside what the temperature is.

Your normal body temperature would be 98.6 °F on the Fahrenheit scale. On the Celsius scale, it would be 37 °C. The Celsius scale is used in most countries, aside from the USA, because it is a part of a metric system.

Project
Ask your parent to allow you to use the house thermometer. Record your temperature. Record the temperature of your body after a cold shower and after a bit of exercise. Can you explain why there is such a big difference?