1. Thermometers This also has a Hygrometer, which measures humidity.

2. Thermometers an instrument for measuring and indicating temperature, typically one consisting of a narrow, hermetically sealed glass tube marked with graduations and having at one end a bulb containing mercury or alcohol which extends along the tube as it expands.

3. A Thermometer measures air temperature.
A Thermometer works because matter expands when heated. Most thermometers are closed glass tubes containing liquids such as alcohol. When air around the tube heats the liquid, the liquid expands and moves up the tube. A scale then shows the actual temperature of the air.

4. 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.

5. 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.