Energy - (GCSE Physics)

Energy

Energy

Energy is a concept in physics which:

• Cannot be created or destroyed.
• Can be transferred, dissipated or stored.
• Is conserved in a closed system.
• Is a quantity you can calculate.
• Is measured in Joules (J).

Systems of Objects

In physics we often used the word ‘system’. A system is an object or group of objects.

Whenever we talk about systems, we are simply referring to the object(s) that we are looking at.

For example, if we’re talking about the process of evaporation of a hot pan of water, the system would be the whole pan including the water, the actual pan, and the heat source.

We can have two types of systems: open or closed.

Open Systems

Open systems are able to exchange energy and matter with their surroundings.

When you boil water in a saucepan, heat energy is able to leave the system in the form of steam. As this energy gets transferred, the system is changing.

Closed Systems

Closed systems are unable to exchange energy and matter with their surroundings.

When you pour coffee into an insulated thermos flask and close the lid, heat energy is unable to leave the system. This means that you have created a closed system, where no energy or matter can be transferred.