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Thermometry and Temperature Conversions


The temperature of a system is defined as simply the average energy of microscopic motions (Average Kinetic Energy) of a single particle in the system per degree of freedom. For a solid, these microscopic motions are principally the vibrations of the constituent atoms about their sites in the solid. For an ideal monatomic gas, the microscopic motions are the translational motions of the constituent gas particles. For multiatomic gases, vibrational and rotational motion should be included too.

Fahrenheit is a temperature scale named after the German-Dutch physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. Where did his scale come from? There are many different version, take a look. LINK

In 1742, Anders Celsius (1701 – 1744) created a "reversed" version of the modern Celsius temperature scale whereby 100 represented the freezing point of water and zero represented the boiling point of water.

The Kelvin scale and the Kelvin are named after the Irish-born physicist and engineer William Thomson, 1st Baron Kelvin (1824 – 1907), who wrote of the need for an “absolute thermometric scale.”

The Kelvin unit and its scale, by international agreement, are defined by two points: absolute zero, and the triple point of specially prepared water (VSMOW) . This definition also precisely relates the Kelvin scale to the Celsius scale. Absolute zero—the temperature at which nothing could be colder and minimal heat energy remains in a substance—is defined as being precisely 0 K and -273.15 C. The triple point of water is defined as being precisely 273.16 K and 0.01 C. This definition does three things:

It fixes the magnitude of the Kelvin unit as being precisely 1 part in 273.16 parts the difference between absolute zero and the triple point of water; It establishes that one Kelvin has precisely the same magnitude as a one-degree increment on the Celsius scale; and It establishes the difference between the two scales’ null points as being precisely 273.15 Kelvins (0 K = -273.15 C and 273.16 K = 0.01 C). Temperatures in Kelvin can be converted to other units per the table at the bottom.


To Fahrenheit To Celsius To Kelvin
Fahrenheit (F)   (F - 32) * 5/9 (F - 32) * 5/9 + 273.15
Celsius (C or o) (C * 9/5) + 32   C + 273.15
Kelvin (K) (K - 273.15) * 9/5 + 32 K - 273.15  

***Note any change in Celsius is the same "change" in Kelvin. The Kelvin scale is 273 units greater than Celsius.

0oC --> 100oC     100 degree change

273 K --> 373 K      100 Kelvin change   

Convert These Temperatures

Problem Highlight to Reveal Answers

(100 * 9/5) + 32 = 212oF

212oF--> K (212 - 32) * 5/9 + 273=     373K
40C --> K 40 + 273=  313K
550oC-->F (550 * 9/5) + 32 =     1022oF
-40oF--> K (-40 - 32) * 5/9 + 273=     233K
2000K --> C 2000 - 273=   1727oC
500K --> F (500 - 273) * 9/5 + 32= 440oF

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