What is the advantage of using temperature units in kelvin?
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The number one advantage of the Kelvin scale over the Celsius and Fahrenheit scales is that it is thermodynamic. That means the Kelvin scale is linear with the 0 point being at absolute zero. That, in turn, means that a temperature of 2T is twice as hot as a temperature of T.
As an example, what temperature is twice as hot as the melting point of ice at standard atmospheric pressure, which occurs at approximately (not exactly)
273.15 K = 0 °C = 32 °F. (All 3 of these temperatures are exactly equal to one another.)
The temperature that is twice as hot is:
546.30 K = 273.15 °C = 523.67 °F.
Notice the Kelvin value is doubled. If we doubled the Celsius value, we would have gotten the same 0 °C, which obviously is not twice as hot. If we double the Fahrenheit value, we would have gotten 64 °F, which is similarly erroneous.
You might ask, “Well, who cares about that?” Here are two applications where the use of a thermodynamic scale, rather than an offset scale, is critical: (1) the ideal gas law and some related laws in chemistry (e.g., doubling the temperature of a gas doubles the pressure if all else is kept constant) involve formulas that include temperature for which use of Celsius or Fahrenheit values would give totally fallacious results, and (2) the speed of sound through a gas is proportional to the square root of the thermodynamic temperature.
As an example, what temperature is twice as hot as the melting point of ice at standard atmospheric pressure, which occurs at approximately (not exactly)
273.15 K = 0 °C = 32 °F. (All 3 of these temperatures are exactly equal to one another.)
The temperature that is twice as hot is:
546.30 K = 273.15 °C = 523.67 °F.
Notice the Kelvin value is doubled. If we doubled the Celsius value, we would have gotten the same 0 °C, which obviously is not twice as hot. If we double the Fahrenheit value, we would have gotten 64 °F, which is similarly erroneous.
You might ask, “Well, who cares about that?” Here are two applications where the use of a thermodynamic scale, rather than an offset scale, is critical: (1) the ideal gas law and some related laws in chemistry (e.g., doubling the temperature of a gas doubles the pressure if all else is kept constant) involve formulas that include temperature for which use of Celsius or Fahrenheit values would give totally fallacious results, and (2) the speed of sound through a gas is proportional to the square root of the thermodynamic temperature.
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