You will be given a definition of a task first, then some input of the task.
Given a scientific question, generate a correct answer to it.

The actual amount (mass) of gasoline left in the tank when the gauge hits "empty" is a lot less in the summer than in the winter. the gasoline has the same volume as it does in the winter when the "add fuel" light goes on, but because the gasoline has expanded, there is what?
Output:
less mass