Many things gain heat when exposed to a hot surrounding and lose heat when the surrounding is cold.
Temperature is measured using a thermometer.
It uses the principle that materials expand when they gain heat and contract when they lose heat.
The most commonly used thermometer is the mercury-in-glass type.
Other types of thermometer are red-dyed alcohol thermometer, ether thermometer, digital thermometer and thermal sensor thermometer.
Mercury is used because it can easily expand or contract when there is a change in temperature, is able to measure higher temperature, does not stick to the glass and can be seen clearly.
The invention of thermometer is attributed to Galileo in 1593, although the sealed type thermometer did not come up into existence until 1650.
Most thermometer are made from glass. They are easily broken.
- do not use thermometer to stir liquids. Use a glass rod or spatula for stirring.
- hold the thermometer vertically when taking the reading. Use the correct way when reading the temperature scale.
- do not touch the bottom part of the beaker or container with the thermometer when measuring temperature.
- do not hold the thermometer on its bulb because the heat from your body will affect the temperature reading.
- be extra careful when clamping a thermometer on the retort stand.
- immediately tell when a thermometer is broken.
Note: Do not play with the mercury or the broken glass. Mercury is a dangerous and poisonous substance.