Because the same liquid is expanded and takes up more room, although it has no more weight.
Why will a gallon of cold water weigh more than a gallon of hot water?
Because a gallon of cold water, when heated, will make more than a gallon of hot water.
When do we get the most molasses, by buying it in hot or in cold weather?
We get the most by buying it in cold weather, because a gallon bought then will make more than a gallon when the weather becomes warmer.
Does heat expand the air and make it lighter?
Heat does expand the air and make it lighter.
What does the air do when heated?
It ascends or rises up, because it is lighter, and the cold or heavier air falls to take its place.
What part of a room, in which there is fire, is the warmest?