# temperature increase

**URL:** <https://boards.straightdope.com/t/temperature-increase/155831>\
**Category:** Factual Questions\
**Created:** [February 18, 2003, 6:59am UTC](https://boards.straightdope.com/t/temperature-increase/155831 "2003-02-18T06:59:31Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Grievar](https://avatars.discourse-cdn.com/v4/letter/g/82dd89/32.png) [@Grievar](https://boards.straightdope.com/u/Grievar)\
**Post date:** [February 18, 2003, 6:59am UTC](https://boards.straightdope.com/t/temperature-increase/155831/1 "2003-02-18T06:59:31Z")

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How can one calculate the temperature increase from compressing  
a gas into half its space?

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [February 18, 2003, 7:21am UTC](https://boards.straightdope.com/t/temperature-increase/155831/2 "2003-02-18T07:21:04Z")

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[Combined Gas Law](http://dbhs.wvusd.k12.ca.us/GasLaw/Gas-Combined.html).

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**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [February 18, 2003, 7:32am UTC](https://boards.straightdope.com/t/temperature-increase/155831/3 "2003-02-18T07:32:33Z")

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> [@](#):
>
> \*Originally posted by friedo \*  
> \*\*[Combined Gas Law](http://dbhs.wvusd.k12.ca.us/GasLaw/Gas-Combined.html). \*\*

That allows you to calculate the temperature of the resulting gas provided you know the pressure. Which you don’t, unless you provide another constraint. There are two approximations often used: one is that the system is isothermal, so that any rise in heat escapes to the surrounding environment and the temperature remains constant. Another is the adiabatic approximation where there is no transfer of heat at all. The real world is usually somewhere in between - some heat is lost to the environment but not all. You can look up the adiabatic formula here:

[http://he.daveb.net/phys47/html/latex2html/node84.html](http://he.daveb.net/phys47/html/latex2html/node84.html)

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [February 18, 2003, 7:47am UTC](https://boards.straightdope.com/t/temperature-increase/155831/4 "2003-02-18T07:47:11Z")

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Yeah, do what **scr4** said.

It’s been too long since I took Chemistry. Lab sessions were so much fun when the teacher wasn’t looking.

😛

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**Author:** ![Grievar](https://avatars.discourse-cdn.com/v4/letter/g/82dd89/32.png) [@Grievar](https://boards.straightdope.com/u/Grievar)\
**Post date:** [February 18, 2003, 8:03am UTC](https://boards.straightdope.com/t/temperature-increase/155831/5 "2003-02-18T08:03:22Z")

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sooo…

g = my shorthand for gamma

adiabatic transformation:

P1 \* V1^g = P2 \* V2^g

using the ideal gas law…

nRT1/V1 \* V1^g = nRT2/V2 \* V2^g

cancel

T1/V1 \* V1^g = T2/V2 \* V2^g

subtract exponents

T1 \* V1^(g-1) = T2 \* V2^(g-1)

assuming an ideal gas:

T1 \* V1^2/3 = T2 \* V2^2/3