8.5KG Gas Cylinders - cost of refill.

hako · Guru

8.5KG Gas Cylinders - cost of refill.

Lancelot Link · Senior Member

but then we have Boyles law:
(P1*V1)/T1=(P2*V2)/T2

Which says, if I remember my chemistry right, Volume depends on temperature and is related to pressure. So if in Darwin in summer versus Melbourne in winter, you will get less gas in Darwin at a higher pressure than in Melbourne with cold temperatures which will give you more gas at the same pressure! But if you buy in Melbourne and take it to Darwin in summer, you will end up with more pressure for the same volume!

RustyD · Guru

Same Boyles Law works for tyre pressure. Never really thought of how much difference pumping a tyre up in zero degrees (273K) vs 40 degrees (313K).

daffyfrancis · Senior Member

Like Hako I am easily fooled but would not 1kg by weight of gas be the same no matter what the pressure?

David

Aus-Kiwi · Guru

Once it liquide ! That's it !

PeterD · Guru

Boyles law has nothing to do with temperature. That's Charles's law. When using Charle's law remember the temperature scale to use is the Kelvin scale.

The ambient temperature between places in Oz does changes very little as a percentage of the temperatures we are working at. That means there is very little change in volume, probably not worth worrying about. It also has nothing to do with the amount of liquid in the bottle. To analyse the situation fully you need to use the ClausiusClapeyron relation. For a simple relationship you can use the equilibrium vapour pressure.

Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system.

Again you need to use the Kelvin scale when working with the coefficient of expansion of the liquid in the bottle. Again the percentage change of temperature is so little that I would not be too worried about the change of volume with the change of temperature.