Hello I'm new here. The reason why I have joined is because I'm working on an invention which I believe will be extremely good for the environment. The question is by how much? My problem is I never paid much attention at school; lessons I’ll be remembering forever include the one, where in biology we had to dissect sheep’s eye balls and mine was the first to go in the rat cage, or when my chemistry teacher got pissed after we put pure ethanol in his coffee (guess it really is tasteless!). And now of course it’s all come back to haunt me, because many formulas, (and most of maths) seems looks more like ancient Egyptian to me, and I have to work really hard to “decode” it. The Question… If a open cubic meter of air at 1 atmosphere is heated from 300 Kelvin to 400 Kelvin (i.e. from 28 to 128 degrees) its volume will expand by 33.33% So logic dictates that if an enclosed meter is heated the same amount then its pressure should increase by 33.33% (i.e. to 1.33 atmospheres) http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/ThermProps.htm (under “Gas Pressure Increase With Temperature”) BUT if I THEN let the pressure DECREASE to 1 atmosphere (i.e. let the gas volume increase by 33.33%) what happens to the temperature? At first you would have thought the temperature would decrease by 33% (i.e. from 400 Kelvin to 277 Kelvin) because pressure and volume are supposed to be proportional. Here is just one link amongst many that say that http://solospirit.wustl.edu/solospirit2/education/Science%20Side/pvt.html [Broken] But then I came across this calculator… http://www.1728.com/combined.htm" [Broken] And entered (under the temperature section) the following… 1. Pressure 1 Equals: 1038.2 2. Volume 1 Equals: 1 3. Temperature 1 Equals: 400 4. Pressure 2 Equals: 760 5. Volume 2 Equals: 1.366 Calculators answer: Temperature 2 = 399.98 (P.S The pressure is in Torr and there are 760 to the atmosphere) Obviously online calculators can be wrong, but if a 100 degree temperature increase can give an unenclosed gas volume an increase of 33%; then if enclosed this gas should still be 100 degrees hot after a 33% pressure decrease. Then again pressure and temperature are supposed to be proportional. So which is right? The calculator, the proportional saying, or even both? This problem really bugs me because it will screw up the design in my patient application should I choose the wrong path. So any help would be very gladely received.