Question

The thermal energy in a heat engine is used to move a piston. Which best describes why this is possible?

Answer 1

These are the choices.

The increase in thermal energy results in an increase in pressure.

The decrease in thermal energy results in an increase in pressure.

The increase in thermal energy results in a decrease in pressure.

The decrease in thermal energy results in a decrease in pressure.

Answer 2

Heat engines burn fuel to create heat. The process of burning fuel involves a chemical reaction called combustion where fuel burns in oxygen in the air to produce carbon dioxide and steam. In external combustion engines, for example, coal is burned to heat water. The steam produced is piped into a strong metal cylinder which moves a tight-fitting plunger called a piston. The back and forth movement of the piston then powers whatever engine it is attached to.