On a serious note does a compressed gas weigh less because there is more of it?
What I’m saying is…if you put a lot of gas under pressure into a vessel does it get proportionally get ter the more volume (higher pressure) you put in?
If so those Bottles of balloon gas, do they get heavier the more you draw-off.
Im all confuwsed nowe
1 mole of gas (a fixed number of molecules, equivalent to the number of molecules in 12grams of carbon12) will occupy a known volume at a known temperature and pressure according tot he following equation known as the ideal gas law (it’s called ideal because it only works on ideal gases, of which there are precicely none, but it’s pretty much accurate most of the time, basicly it doesnt account for the intra molecular forces pullign molecules together or the fact that you can’t compress them entirely as the molecules take up some space).
PV=nRT
P= pressure
V=volume
n= number of moles
R= ideal gas constant
T= temperature
So if you double the pressure then you have to have double the number of moles thus double the weight, tyres run at about 2 bar (guage, i.e. relative to the atmosphere), atmosphere is about 1 bar, so the air in your tyre is 3x heavier than the air outside.
However 1 mole of helium weighs a lot less than 1 mole of ‘air’ as each molecule weighs a lot less. Thus to get the same pressure in the same volume at the same temperature you need the same moles, but less mass.
The problem is that smaller/lighter molecules can pass through the gaps between the rubber molecules in the innertube.
Alternatively you could heat your tyres upto 3x the temperature, to get a siilar effect but no ones figured out how to maintain tyres at 600degC.
