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Temperature is a measure of how hot or cold something is which is the result of
the motion of particles which make up a substance. Temperature increases as the
energy of this motion increases.
The basic unit of temperature in the International System of Units (SI) is the
kelvin (K). The Kelvin and Celsius temperature scales are defined by two
points: absolute zero and the triple point of specially prepared water.
Absolute zero is defined as being precisely 0 K and -273.15 °C where all
kinetic motion in the particles comprising matter ceases and they are at
complete rest. It contains no thermal energy.
The Fahrenheit scale, named after german physicist Gabriel Fahrenheit
(1686-1736), is based on the melting point of ice (32 degrees above 0) and the
boiling point of water (212 degrees above 0). The Celsius scale, named after
sweedish astronomer in 1742, is based on 0 degree as freezing point of water
and 100 degrees as the boiling point. The Kelvin scale, named after british
physicist Lord Kelvin (1824-1907) and the Rankine scale named after William
Rankine, is based on thermo dynamic principles where 0 equals to -459.4 degrees
fahrenheit. The Reaumur scale, named after R.A.F de Reaumur (1683-1757), sets
the freezing point of water at 0 degree and the boiling point at 80 degrees.
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