Celsius scale of temperature

Anders Celsius, a Swedish astronomer, introduced his scale in 1742. To define the scale he used the freezing point of water as 100 and the boiling point as zero. [After his death they reversed it!]

For a long time, the Celsius scale was called 'centigrade'. The Greek prefix centi- means one-hundredth and each degree Celsius is one-hundredth of the way between the temperatures of freezing and boiling for water. The Celsius temperature scale is part of the standard international system of measurement (SI) and is used throughout the world, except in public places in the US. (American scientists use the SI system.)

A more 'natural' zero point is the point at which all available energy has been removed from a substance. This temperature (minus 273.15 degrees Celsius) is called absolute zero. No temperature is below that. Adding 273.15 degrees to the Celsius temperature gives the temperature in Kelvins. Room temperature in Bangkok is ~300 K.

The Kelvin scale is used for all calculations using the ideal gas equation....