I have read that gasoline expands and you pay more for less in hot weather is it the sample for propane?

Gasoline pumps compensate for density variations that occur due to temperature, and in doing so, they measure the amount (m) of gasoline dispensed. Yet, a gallon of cold gasoline will occupy less volume than when hot. In essence, the measurement of a gallon of gasoline actually refers to its volume at a given temperature (such as 60 degF). As such, this is really a m measurement unit because it refers to the flow of the gasoline at a given temperature, rather than the volume being dispensed. A gallon is not always a gallon at the gas pump, sometimes it is a little more, sometimes it is a little less. But a gallon of gas, as measured by the pump, will WEIGH the same whether you buy it in the middle of the summer in Phoenix or the middle of the winter in Anchorage. Propane works the same way, a 20lb tank of propane is 20lbs at a specific temperature.