Kelvin: Difference between revisions
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<onlyinclude>'''Kelvin''' is the [[SI]] base [[units|unit]] of [[temperature]].<ref>Russ Rowlett. (2002). ''A Dictionary of Units of Measurement - Kelvin'' [Online]. Available: http://www.unc.edu/~rowlett/units/dictK.html#kelvin [February 27, 2015] </ref> It is given the symbol <math>K</math>.</onlyinclude> Since temperature measures the [[energy]] of atoms and molecules, a true temperature scale must be a positive scale since atoms cannot have a negative energy. On the Kelvin scale, 0 Kelvin is the temperature of [[absolute zero]]. Absolute zero is the temperature in a system where all particles stop moving (ignoring some important [[quantum mechanics]]). A degree Kelvin and a degree [[Celsius]] are the same ''unit'', as they have the same "spacing" between each degree, but the scales have different zero points (see converter below). | <onlyinclude>'''Kelvin''' is the [[SI]] base [[units|unit]] of [[temperature]].<ref>Russ Rowlett. (2002). ''A Dictionary of Units of Measurement - Kelvin'' [Online]. Available: http://www.unc.edu/~rowlett/units/dictK.html#kelvin [February 27, 2015] </ref> It is given the symbol <math>K</math>.</onlyinclude> Since temperature measures the [[energy]] of atoms and molecules, a true temperature scale must be a positive scale since atoms cannot have a negative energy. On the Kelvin scale, 0 Kelvin is the temperature of [[absolute zero]]. Absolute zero is the temperature in a system where all particles stop moving (ignoring some important [[quantum mechanics]]). A degree Kelvin and a degree [[Celsius]] are the same ''unit'', as they have the same "spacing" between each degree, but the scales have different zero points (see converter below). | ||
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Temperature is a measure of the [[kinetic energy]] of molecules in a system, and using Kelvin units are essential to explaining this concept clearly. Temperature can be related to energy through a value known as the [[Boltzmann's constant|Boltzmann constant]]. This constant is derived from the ideal gas law, given by the equation <math>KE_{avg}=\frac{3}{2}k_b T</math> where <math>k_b </math> is the Boltzmann constant, <math>1.38064\times10^{-23}</math> [[joule|J]]/K. | Temperature is a measure of the [[kinetic energy]] of molecules in a system, and using Kelvin units are essential to explaining this concept clearly. Temperature can be related to energy through a value known as the [[Boltzmann's constant|Boltzmann constant]]. This constant is derived from the ideal gas law, given by the equation <math>KE_{avg}=\frac{3}{2}k_b T</math> where <math>k_b </math> is the Boltzmann constant, <math>1.38064\times10^{-23}</math> [[joule|J]]/K. | ||
Many calculations with temperature require using an absolute scale like the Kelvin scale. For example if a temperature of 27°C is doubled, it needs to be expressed as an absolute value. In other words, you cannot just multiply 27°C by 2. The correct calculation is shown below: | |||
<center><math> 2 \times (27°C + 273) = 2 \times (300 K) = 600 K = 327°C </math></center> | |||
Likewise, if there's a 1% increase in a temperature of 27°C, we need to convert to Kelvin first. The calculation below shows that the increase in temperature is '''not''' 0.27°C, but that it's actually a 3°C warming to 30°C: | |||
<center><math> 1.01\times (27°C + 273) = 1.01 \times (300 K) = 303 K = 30°C </math></center> | |||
==Conversions== | ==Conversions== | ||
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*[[Zeroth law of thermodynamics]] | *[[Zeroth law of thermodynamics]] | ||
*Or explore a [[Special:Random|random page]] | *Or explore a [[Special:Random|random page]] | ||
To read more about Kelvin, please look at [http://www.unc.edu/~rowlett/units/dictK.html#kelvin | To read more about Kelvin, please look at Dr. Rowlett's [http://www.unc.edu/~rowlett/units/dictK.html#kelvin unit dictionary] or [http://chemwiki.ucdavis.edu/Analytical_Chemistry/Temperature_Basics UC Davis's Chemistry wiki]. | ||
==References== | ==References== | ||
{{reflist}} | {{reflist}} | ||
[[Category:Uploaded]] | [[Category:Uploaded]] | ||
Latest revision as of 00:02, 27 September 2021
Kelvin is the SI base unit of temperature.[1] It is given the symbol . Since temperature measures the energy of atoms and molecules, a true temperature scale must be a positive scale since atoms cannot have a negative energy. On the Kelvin scale, 0 Kelvin is the temperature of absolute zero. Absolute zero is the temperature in a system where all particles stop moving (ignoring some important quantum mechanics). A degree Kelvin and a degree Celsius are the same unit, as they have the same "spacing" between each degree, but the scales have different zero points (see converter below).
Kelvin is usually avoided for everyday use, instead it is always used for temperatures in physics (and also often in chemistry), in equations such as the ideal gas law. If a gas had a temperature of -52.15°C (220 K) the negative number would make no sense in the ideal gas law.
Temperature is a measure of the kinetic energy of molecules in a system, and using Kelvin units are essential to explaining this concept clearly. Temperature can be related to energy through a value known as the Boltzmann constant. This constant is derived from the ideal gas law, given by the equation where is the Boltzmann constant, J/K.
Many calculations with temperature require using an absolute scale like the Kelvin scale. For example if a temperature of 27°C is doubled, it needs to be expressed as an absolute value. In other words, you cannot just multiply 27°C by 2. The correct calculation is shown below:
Likewise, if there's a 1% increase in a temperature of 27°C, we need to convert to Kelvin first. The calculation below shows that the increase in temperature is not 0.27°C, but that it's actually a 3°C warming to 30°C:
Conversions
For Further Reading
To read more about Kelvin, please look at Dr. Rowlett's unit dictionary or UC Davis's Chemistry wiki.
References
- ↑ Russ Rowlett. (2002). A Dictionary of Units of Measurement - Kelvin [Online]. Available: http://www.unc.edu/~rowlett/units/dictK.html#kelvin [February 27, 2015]