Has your hand ever been so cold that it went numb? Well how about when it was 90o and you were outside in the sun, no, well this has happened to me before. Over the summer I worked part time at clover home leisure. Part of my job was to fill up propane tanks. Normally not a big deal, but sometimes we get massive propane tanks with purge valves. While filling, the purge valve forces the air out. When tank is done filling, the purge value starts spitting out massive amounts of propane. Propane stored in the tanks is very very cold to allow more gas to be stored. So I have to reach my hand into the cloud of propane gas and twist the purge valve shut as it is spitting out the ice cold propane(frost will literally form on the tank while I shut the value) . So one day a guy came in with 14 of these purge tanks. By the time I had finished filling the tanks my hand had been frozen and thawed and refrozen and rethawed far too many times. So my story kinda got away from me so I should probably relate this to physics. Thermodynamics was included in our physics class last year and as we learned PV=nRT. From this equation we get that n, the number of moles or amount of gas is inversely proportional to the temperature. If we want to put as much gas into the tank as possible we have three options, cool the gas down, make stronger tanks that can withstand more pressure, or alter the fabrics of the universe so that the gas constant R is a smaller value. Naturally cooling the gas is the most wildly used method (altho for my hand’s sake I’d prefer if we invested in the third option). Thus this is the reason why the propane gas is so cold when stored in a fuel tank.