1.1.1 Energy Stores & Transfers

• In physics, a system is defined as an object or group of objects.
• When a system is in equilibrium, nothing changes and so nothing happens.
• Energy is measured in units of joules (J).
• A thermodynamic system can be isolated, closed or open.
• An open system allows the exchange of energy and matter to or from its surroundings.
• A closed system can exchange energy but not matter to or from its surroundings.
• An isolated system does not allow the transfer of matter or energy to or from its surroundings.
• Energy is stored in objects.
• When a change happens within a system, energy is transferred between objects or between stores.
• Energy cannot be created or destroyed, it can only be transferred from one store to another.
• For a closed system, the total amount of energy is constant.
• Energy is transferred between stores via transfer pathways.