Helium.
because that's what it is?Liquefied Petroleum Gas = LPG
LPG: Liquefied Petroleum Gas CNG: Compressed Natural Gas
gas
by compressing it
No. It takes a combination of pressure and temperature to liquefy some gases. Hydrogen and helium were the last gases to be liquefied and that was with pressure and extremely low temperature.
NGL is not liquefied natural gas, which is condensed natural gas that is compact and therefore convenient for overseas shipping.
You cool it down.
Yes.
That the gas has liquefied.
Carbon dioxide (CO2) can be liquefied under pressure at ordinary temperature.
lpg
sometimes