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Temperature converter

oC (Celsius) K (Kelvin) oF (Fahrenheit)

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With this program, the units of temperature (degrees Celsius, Kelvin and degrees Fahrenheit) can be converted.

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Definition of temperature:

The tendency of a substance or an object to transfer heat to its surroundings.

Definition of the thermodynamic temperature:

The Kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water (13de CGPM (1967), Rés. 4)
Reference: http://www.nmi.nl/english/about_metrology/quantities_and_units/definition_of_the_basic_units.htm
Reference: http://physics.nist.gov/cuu/Units/current.html

In the 13th CGPM in 1967 was decided that the unit of temperature will be the Kelvin, and not 'degrees Kelvin'. The triple point of water is 273.16 K, which is 0.01 oC (degrees Celsius).

Definition of Celsius:

The Celsius-scale is defined by the follow two points:

  1. The triple point of water is defined as 0.01 oC.
  2. One degree Celsius equals the change of temperature with one degree on the ideal gas-scale.

The triple point is a theoretical point where the three phases of a matter (for example water) come together. This means that liquid, solid and gas phase from a matter appear at the same time. This is practically impossible.

History of measuring temperature:

The idea of measuring temperature exists a long time. One of the first who wanted to make a temperature scale was Galen (ca. 170). He had a scale of 4 degrees warmth and 4 degrees of cold. The earlier measurement instruments for temperature where called thermo scopes. In 1610 Galileo introduced wine in the thermo scopes instead of air. In 1724 Gabriel Fahrenheit introduced the medium mercury in the thermo scopes. The reason that mercury was used is that the thermal expansion of mercury is large, mostly homogeneous and it does not stick on the glass. Mercury also stays in the liquid phase for a great range of temperature. It is also easy to read.

Present temperature scales:

Present temperature scales have two basic points: from when the water starts to freeze and when it starts to boil. Between these two temperatures a scale is made. The two most popular scales are the Celsius (made by Anders Celsius) and Fahrenheit (made by Gabriel Fahrenheit) scale. The Fahrenheit scale is defined so that the melting point of water lays by 32 degrees Fahrenheit and the boiling point lays by 212 degrees Fahrenheit. This means that between the freezing point and boiling point there are 180 divisions. Fahrenheit introduced his scale in 1724.

Another scale is the Celsius scale. In the Celsius scale the freezing point of water is set at 0 degrees (centigrade) and the boiling point at 100 degrees (centigrade). This scale exists on 100 divisions, also known as centiscale. In 1948 the centidegrees (centigrade scale) were replaced by the degrees Celsius (oC). The Celsius scale is defined by the following two points:

  1. The triple point of water is defined at 0.01 oC.
  2. One degree Celsius equals the change of temperature with one degree on the ideal gas-scale.

On the Celsius-scale the boiling point of water with a pressure of 1 atmosphere is set at 99.975 oC. With the centiscale it was 100.

SI temperature scale:

Temperature is related with the kinetic energy of the molecules. The kinetic energy changes when the temperature changes. Temperature is defined as the translation of heath between two objects. The fundamental temperature scale is the one of Kelvin. The temperature scale of Kelvin depends of the absolute zero point. This is the point where the molecules do not move anymore, so they do not give warmth. This is for all molecules. The absolute zero point is by 0 K, this is -273.15 oC. The scale is the same as the Celsius.

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Suggested reading for the topic: Mercury

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