AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Energy stores and systems: There are changes in the way energy is stored when a system changes.
When a system changes, energy is transferred between stores rather than being used up.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
When a system changes, energy is transferred between stores rather than being used up. A system is an object or group of objects. In a closed system, no energy transfers in or out, so the total energy remains exactly the same, though the way it is stored changes. For example, a falling book in a vacuum transfers energy from its gravitational potential store to its kinetic store. In an open system, energy can be transferred to the surroundings. A battery-powered lamp transfers energy from a chemical store to a thermal store in the filament and to the surroundings by heating and radiation. To describe a change, name the decreasing store, the increasing store, and the pathway (mechanical work, electrical work, heating or radiation).
What earns the marks
- States that when a system changes, energy is transferred between stores rather than created or destroyed.
- Identifies the store that decreases and the store that increases during a described change.
- Names the transfer pathway, such as mechanical work, electrical work, heating or radiation.
- Applies conservation of energy to a closed system, stating that no energy transfers in or out, so the total energy remains constant.
- Uses a concrete example, such as lifting a book or a falling ball, to describe the store changes.
Common mistakes and how to put them right
Saying energy is 'used up' or 'lost'.
Put it right: Energy is transferred to other stores, including thermal stores in the surroundings.
Listing only one store change.
Put it right: Describe both the store that decreases and the store that increases.
Confusing a closed system with an open system.
Put it right: A closed system has no energy transfer to or from the surroundings, whereas an open system does.
Exam tips
- Use the pattern 'energy is transferred from the ... store to the ... store by ...' in your answer.
- If the question specifies a closed system, state that the total energy before the change equals the total energy after.
Try the lesson
The start of the Energy stores and systems: There are changes in the way energy is stored when a system changes. lesson, made from checked teaching notes for this specification point.
Have a go first
A book is lifted from a table and held higher above the floor. Which energy store of the book increases as it is lifted?
Listen
When a system changes, energy is transferred between stores rather than being used up. A system is an object or group of objects. In a closed system, no energy transfers in or out, so the total energy remains exactly the same, though the way it is stored changes. For example, a falling book in a vacuum transfers energy from its gravitational potential store to its kinetic store. In an open system, energy can be transferred to the surroundings. A battery-powered lamp transfers energy from a chemical store to a thermal store in the filament and to the surroundings by heating and radiation. To describe a change, name the decreasing store, the increasing store, and the pathway (mechanical work, electrical work, heating or radiation). A strong answer earns marks for these points. States that when a system changes, energy is transferred between stores rather than created or destroyed. Identifies the store that decreases and the store that increases during a described change. Names the transfer pathway, such as mechanical work, electrical work, heating or radiation. Applies conservation of energy to a closed system, stating that no energy transfers in or out, so the total energy remains constant. A common slip: Saying energy is 'used up' or 'lost'. Instead, energy is transferred to other stores, including thermal stores in the surroundings. Exam tip: Use the pattern 'energy is transferred from the ... store to the ... store by ... in your answer.
See it
Key words
Say what each word means before you turn the card.
Conservation of energy
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Energy stores and pathways
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Changes in a system
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Closed systems
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See every definition
- Conservation of energy
- When a system changes, energy is transferred between stores rather than created or destroyed.
- Energy stores and pathways
- To describe a change, name the decreasing store, the increasing store, and the pathway by which energy is transferred.
- Changes in a system
- There are changes in the way energy is stored when a system changes.
- Closed systems
- No energy transfers in or out, so the total energy remains exactly the same, though the way it is stored changes.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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