B4 Thermodynamics

What is an open system?

A system that can exchange thermal energy (heat), work and matter (mass) with its surroundings. An example could be a jet engine directing hot gas behind an aeroplane.

What is a closed system?

A system that can exchange thermal energy or work with its surroundings, but not matter. An example might be a metal container with warm gas inside, cooling down.

What is an isolated system?

A system that cannot exchange thermal energy, work or matter with its surroundings. An example might be a very effective thermos flask that is well insulated.

What is the sign of W when work is done BY the gas?

Positive, it is expanding

What is the sign of W when work is done ON the gas?

Negative- it is being compressed