Themometer is used to measure the temperature of an object.Galileo invented a rudimentary water thermometer in 1593.He called this device a thermoscope.However,this form was effective as water freezed at low temperatures.In 1714,Gabriel Fahrenheit invented the modern mercury thermometer. A thermometer consists of a long,narrow,uniform glass tube called the stem.The scales in which the temperature is measured are marked on the stem.At the end of the stem, there is a small bulb which contains mercury in it.A capillary tube is inside the glass stem in ehich mercury expands when the bulb is kept contact with a hot body.
Mercury is the only one in liquid state at room temperature.It’s used in thermometers because it has high coefficient of expansion. Hence,the slighest change in temperature is notable when it’s used in a thermometer.It also has a high boiling point which makes it very suitable to measure higher temperatures.Also,it has a shiny appearance and doesn’t stick to the surface of glass.
Mercury is toxic,and it is very difficult to dispose it when the thermometer breaks.So,nowadays digital thermometers are used to measure the thermometers ,as they do not contain mercury.
