Changes

The term '''absolute temperature scale''' usually refers to the [[Kelvin]] temperature scale, but can also refer to the [[Rankine]] scale. These scales are based on the conventional scales for measuring temperature - [[Celsius]] in most non-US countries and [[Fahrenheit]] in the [[United States]].

The term '''absolute temperature scale''' usually refers to the [[Kelvin]] temperature scale, but can also refer to the [[Rankine]] scale. These scales are based on the conventional scales for measuring temperature – [[Celsius]] in most non-US countries and [[Fahrenheit]] in the [[United States]].

==Need for an absolute scale==

==Need for an absolute scale==

Chemists and physicists working with [[gas]]es came to the realization that the conventional temperature scales were not adequate for characterizing the effect of temperature on the decrease in [[volume]] and [[pressure]] of gases with the corresponding decrease in the actual temperature of the gases.

Chemists and physicists working with [[gas]]es came to the realization that the conventional temperature scales were not adequate for characterizing the effect of temperature on the decrease in [[volume]] and [[pressure]] of gases with the corresponding decrease in the actual temperature of the gases.

Ultimately, they realized that if they could decrease the temperature of an [[Ideal Gas|ideal gas]] to a point where all [[molecular motion]] ceased, that would be a good "[[absolute zero]]" point. They found that this temperature would be -273.16 °C (-459.6 °F).

Ultimately, they realized that if they could decrease the temperature of an [[Ideal Gas|ideal gas]] to a point where all [[molecular motion]] ceased, that would be a good "[[absolute zero]]" point. They found that this temperature would be -273.15 °C (-459.67 °F).

==Kelvin scale==

==Kelvin scale==

The Kelvin scale, which is based on the Celsius scale, sets the absolute zero point at 0 Kelvin (or just 0K).

The Kelvin scale, which is based on the Celsius scale, sets the absolute zero point at 0 Kelvin (or just 0K).

Thus, the melting point of water would be 273.16 K (0 °C + 273.16). Likewise, the boiling point of water is 373.16 K (100 °C + 273.16).

Thus, the melting point of water would be 273.15 K (0&nbsp;°C + 273.15).<ref name="Britannica">[https://www.britannica.com/science/kelvin Kelvin] (www.britannica.com)</ref> Likewise, the boiling point of water at pressure 1 atm is 373.15 K (100&nbsp;°C + 273.15) and the [[triple point]] of water is at 273.16 K.

==Rankine scale==

==Rankine scale==

Like the Kelvin scale, the absolute zero temperature on the Rankine scale is at its zero point - 0°R. However, one degree on the Rankine scale is one degree on the Fahrenheit scale.

Like the Kelvin scale, the absolute zero temperature on the Rankine scale is at its zero point - 0°R. However, one degree on the Rankine scale is one degree on the Fahrenheit scale.

Thus, the freezing point of water would be 491.6 °R (32&nbsp;°F + 459.6), and the boiling point of water would be 671.6 °R (212&nbsp;°F + 459.6).  

Thus, the freezing point of water would be 491.67 °R (32&nbsp;°F + 459.67), and the boiling point of water would be 671.67 °R (212&nbsp;°F + 459.67).  

 

[[Category:Units of Temperature]]

[[Category:Units of Temperature]]