AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Internal energy is the total kinetic energy and potential energy of all…
Full specification wording
Internal energy: Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.
Internal energy has two parts.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 2 of 4
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Internal energy has two parts. The kinetic part comes from the motion of the particles, vibrating in a solid or moving around in a liquid or a gas, and it is this part that temperature measures, so raising the temperature raises the mean kinetic energy of the particles. The potential part comes from the separations of the particles and the forces between them, so pulling particles further apart against their mutual attraction increases it. Internal energy is the total of both parts for every particle in the system. Separating them is what makes changes of state make sense: when liquid nitrogen boils at constant temperature, the mean kinetic energy does not change but the potential energy rises sharply, so internal energy increases.
What earns the marks
- Internal energy as the total of the kinetic and potential energies of all the particles.
- The kinetic part being linked to the temperature of the system.
- The potential part being linked to the separation of the particles.
- A change of state raising the potential energy while the kinetic energy stays the same.
Common mistakes and how to put them right
Saying internal energy is only the kinetic energy of the particles.
Claiming the kinetic energy of the particles rises during boiling even though the temperature is constant.
Confusing the potential energy of the particles with the gravitational potential energy of the whole object.
Giving the change for a single particle when the question asks about the total for the system.
Exam tips
- Split any internal energy answer into a kinetic sentence and a potential sentence.
- If the temperature is constant, say that the kinetic part is constant before mentioning the total.
- Watch for dependent marks, because the conclusion about internal energy usually needs both earlier points.
Try the lesson
The start of the Internal energy: Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system. lesson, made from checked teaching notes for this specification point.
Have a go first
Which of the following is the correct definition of the internal energy of a system?
Listen
Internal energy has two parts. The kinetic part comes from the motion of the particles, vibrating in a solid or moving around in a liquid or a gas, and it is this part that temperature measures, so raising the temperature raises the mean kinetic energy of the particles. The potential part comes from the separations of the particles and the forces between them, so pulling particles further apart against their mutual attraction increases it. Internal energy is the total of both parts for every particle in the system. Separating them is what makes changes of state make sense: when liquid nitrogen boils at constant temperature, the mean kinetic energy does not change but the potential energy rises sharply, so internal energy increases. A strong answer earns marks for these points. internal energy as the total of the kinetic and potential energies of all the particles. the kinetic part being linked to the temperature of the system. the potential part being linked to the separation of the particles. a change of state raising the potential energy while the kinetic energy stays the same. Exam tip: Split any internal energy answer into a kinetic sentence and a potential sentence.
Key words
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internal energy
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kinetic energy of particles
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potential energy of particles
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See every definition
- internal energy
- The total kinetic energy and potential energy of all the particles that make up a system.
- kinetic energy of particles
- The part that comes from the motion of the particles, and it is this part that temperature measures.
- potential energy of particles
- The part that comes from the separations of the particles and the forces between them.
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