What is temperature and how is it measured?

1 Answer
Jul 17, 2015

Temperature is the kinetic energy of the particles of a substance.


The more kinetic energy a particle has the higher it's temperature. In the case of the atmosphere, which is what we are primarily concerned with in Meteorology, we measure this using a mercury thermometer (in certain situations we use an alcohol thermometer and of course modern times have given us things like dewcells and digital thermometers but we always go back to the mercury thermometer for accuracy).

The higher the temperature of a particle the more energy it transfers when it comes into contact with another particle. This transfer is called heat. In a mercury thermometer, heat transfers from the atmosphere into the mercury. This increase in energy in the mercury atoms causes them to vibrate faster which causes the volume of the mercury to change. This is called thermal expansion.

The thermal expansion of mercury is a known amount, so by measuring the expansion of the mercury we measure the increase in temperature. In a thermometer the mercury bulb at the bottom has only one way to expand and that is up the tube of the thermometer. The distance up the tube that the mercury travels is therefore an accurate measurement of how much the mercury has expanded.