For traditional glass thermometers:
* Mercury: Historically, mercury was the most common liquid due to its consistent expansion and contraction with temperature changes, and its visibility. However, mercury is toxic, so its use is now largely phased out.
* Alcohol (usually colored red or blue): Alcohol is less toxic than mercury and has a lower freezing point, making it suitable for measuring colder temperatures.
For digital thermometers:
* No liquid: Digital thermometers don't use liquids. They rely on a thermistor, a small electronic sensor that changes resistance with temperature.
Other types of thermometers may use:
* Gallium: A metal with a low melting point, used in some specialized thermometers.
Note: It's important to handle mercury thermometers with extreme care and dispose of them properly if you have one.
