There are two types of thermometer: a mercury/alcohol thermometer and a spring thermometer.
The mercury or alcohol is placed within a glass. Both these expand when the temperature rises and contracts as it cools. So within the thermometer, the mercury or alcohol is forced upwards when it is warm and then falls as it cools. The glass is marked with degrees of heat, so it is easy to read the temperature which has been reached.
A spring thermometer works by having a piece of metal which is coiled and fixed to a pointer. The metal is sensitive to heat, so as the temperature rises, the metal expands and moves the pointer to the temperature reached.
The spring thermometer is less widely used and is not as accurate. Digital thermometers now electronically read temperatures which replace both the traditional types of thermometers. These are much more accurate and used particularly within medical settings where accuracy is extremely important.
The mercury or alcohol is placed within a glass. Both these expand when the temperature rises and contracts as it cools. So within the thermometer, the mercury or alcohol is forced upwards when it is warm and then falls as it cools. The glass is marked with degrees of heat, so it is easy to read the temperature which has been reached.
A spring thermometer works by having a piece of metal which is coiled and fixed to a pointer. The metal is sensitive to heat, so as the temperature rises, the metal expands and moves the pointer to the temperature reached.
The spring thermometer is less widely used and is not as accurate. Digital thermometers now electronically read temperatures which replace both the traditional types of thermometers. These are much more accurate and used particularly within medical settings where accuracy is extremely important.