Are you hot or cold? A thermometer will take your temperature. There are many different kinds used for different purposes. Take your pick.
One type of thermometer has a thin glass tube partly filled with liquid. When the air is warm, the liquid in the tube becomes warm and rises. It rises because heat makes a liquid expand, or take up more space. The warmer it gets, the more space it needs. When the temperature drops, the liquid contracts, or takes up less space, so it moves down the tube. The liquid in many thermometers is a silver-coloured metal called mercury. Some thermometers are filled with coloured alcohol.
A digital thermometer has a metal probe. When the thermometer is turned on, a battery inside sends around an electric current. If the probe is warm, the current will move easily. If the probe is cool, the current will not move as easily. The thermometer shows a temperature reading based on how easily the current moves.
Doctors often use an IR thermometer to detect infrared rays from a person’s eardrum. The hotter you are, the more radiation the thermometer detects. The thermometer converts the amount of radiation to a temperature reading.
Standard thermometer contains a liquid that moves up when it becomes warm. The liquid drops down when it cools. The lines indicate the temperature.
The lines and numbers on the thermometer indicate degrees. They tell you how much the temperature changed. Degrees are marked with the symbol º. The number 0 ºC is the temperature at which water freezes. This is the same temperature as 32 ºF. The letter C stands for Celsius, and the letter F stands for Fahrenheit.
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