Name two ways to change a gas into a liquid…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- Name two ways to change a gas into a liquid.
- Use them to explain why cooking gas is sold in a cylinder as a liquid.
- When gas rushes out of a cylinder for a long time, the cylinder feels cold. Why?
Need a reminder? The key ideaShow
A gas can be turned into a liquid by compressing it (pushing its particles together) and by cooling it (slowing them down). LPG is kept as a liquid under pressure in a cylinder; the liquid takes about times less space than the gas.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Compress the gas, so that its particles are pushed close together, and cool it, so that its particles slow down. Then the pull between the particles can hold them as a liquid.
Step 2. (b) LPG is compressed until it becomes a liquid. A liquid takes far less space than the gas, so a small cylinder holds a lot of fuel. When the valve opens, the pressure falls and the liquid turns back into gas.
Step 3. (c) Turning the liquid into gas needs latent heat of vaporisation. The liquid takes this heat from the cylinder, so the cylinder cools.
Answer: (a) Compressing and cooling. (b) Under pressure it is a liquid, which takes little space. (c) The evaporating liquid takes heat from the cylinder.
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