Energy stores and systems

The eight named stores, the four ways energy transfers, and the precise mark-scheme language that turns understanding into marks.

SPEC 4.1.1.1 • ENERGY — STORES & SYSTEMS

Why This Lesson Matters

The whole of GCSE Physics is built on energy — and the way you talk about energy is how examiners decide whether you understand it. Use the wrong words, and the marks don't come — even if your physics is right.

8

Named Stores

4

Ways To Transfer

1

Conservation Rule

By the end of this lesson

You'll name all 8 energy stores, list the 4 transfer mechanisms, describe a change using mark-scheme language, and avoid the made-up store names that lose marks every year.

What is a System?

Before you can describe how energy changes, you need to decide what you're looking at. That choice is called the system.

System

A system is an object or group of objects.

Examples

A car is a system.

A car plus its surroundings is a bigger system.

A kettle, the water inside it, and the air around it can all be one system.

Choosing the system is the first step to thinking clearly about energy. It tells you which stores matter, and where energy can leave to.

Energy Stores

Energy is held in stores, not in objects. When something changes, energy transfers between stores — it is never used up.

Energy Store

A way energy is held in a system. There are eight named stores — and only these eight count in a mark scheme.

Energy Transfer

Energy moving between stores.

The 8 Named Stores

Memorise all eight by name. In every answer about energy, the store name needs to come from this list.

Kinetic

Moving things

Gravitational

Height in a gravity field

Elastic

Stretched / compressed objects

Thermal

Vibrating particles

Chemical

Bonds in fuel, food, batteries

Magnetic

Magnetic fields

Electrostatic

Electric fields / charges

Nuclear

Atomic nuclei

Mark-scheme rule

Only these eight names are credited. Anything outside this list — "movement energy", "heat energy", "hydroelectric energy", "electrical energy" as a store — loses the mark, even if your physics reasoning is right.

What Are NOT Stores

Three made-up names cost marks every year. None of them is on the list of eight.

✗ Wrong (no marks)Why it's wrong✓ Use instead

"Movement energy"Not a named storeKinetic

"Heat energy""Heating" is the process ; the store is thermalThermal

"Hydroelectric energy"Hydroelectric is a way of generating electricity, not a storeGravitational (water held up)

"Electrical energy" (as a store)Electricity is a transfer , not where energy is heldChemical (in cell) → transfer by current

The 4 Ways Energy Transfers

Between any two stores, energy moves by one of four mechanisms. Together with the eight stores, these describe almost any process in GCSE Physics.

Heating

Energy moves from a hotter object to a cooler one.

Work done by a force

A force pushes or pulls something through a distance.

Work done by a current

A current flows through a component (every electrical appliance).

Radiation

Energy carried by light, sound, or other waves.

Mark-scheme phrasing

Always pair a store with a mechanism: e.g. "energy is transferred from the chemical store of the fuel to the kinetic store of the car by work done."

Spec note

Spec 4.1.1.1 specifically names three mechanisms (heating, work by force, work by current) for the calculations in this section. Radiation is the fourth way energy transfers and is credited in describe-questions, but the equations for radiation come later in Topic 6 (Waves).

Worked Example — Ball Thrown Upwards

The classic energy-stores question. Track the stores at start, top, and landing.

Chain

Kinetic → gravitational → kinetic → thermal (of ball, ground & air). Transfer mechanism: work done by gravity; throughout the flight some energy is dissipated to the thermal store of the air by drag.

Worked Example — Boiling a Kettle

An everyday system: power station → wires → kettle → water. Trace the stores and the mechanisms that move energy between them.

Chemical

(transfer by current)

Thermal

Full sentence (mark-scheme style)

"Energy is transferred from the chemical store of the fuel to the thermal store of the water in the kettle, by work done when a current flows through the heating element."

Notice

Some energy is also dissipated to the thermal store of the surroundings (the kettle body, the air). The total stays the same — but not all of it ends up in the water.

Worked Example — Car Braking

A car is moving, the driver brakes, the car slows down and stops. Where does the energy go?

Kinetic

(work done by friction)

Thermal

✗ Wrong

"The kinetic energy is lost."

"Lost" suggests it disappears — that breaks conservation. Mark scheme rejects this.

✓ Correct

"The kinetic energy of the car is dissipated to the thermal store of the brakes and the surroundings."

Names the destination store. Uses the credited verb.

All 5 Spec-Named Situations

Spec 4.1.1.1 explicitly names five situations you must be able to describe in terms of energy stores. The first three were worked through above — here is the complete set, all in one place.

SituationEnergy chainMain mechanism

Object projected upwardsKinetic → gravitational → kinetic → thermal (of ball, ground & air)Work done by gravity (& air resistance)

Object accelerated by a constant forceChemical (fuel/cell) → kinetic of objectWork done by the force

Vehicle slowing downKinetic of car → thermal of brakes & surroundingsWork done by friction

Moving object hitting an obstacleKinetic → thermal (mainly) + sound (radiation); some temporarily to elastic if it deforms and reboundsWork done by contact force

Boiling water in an electric kettleChemical (at power station) → thermal of water (and surroundings)Work done when a current flows

Memorise these

A 3- or 4-mark "describe the energy changes" question on Paper 1 will almost always pick one of these five contexts. Knowing the chain and the mechanism for each is guaranteed-mark territory.

Conservation of Energy

Energy is never created and never destroyed — it only moves between stores. This is the single most important rule in physics.

Closed System

A system in which no net energy enters or leaves. The total energy is constant.

What this means

In a closed system, every change just moves energy between stores inside the system. The total at the end equals the total at the start — even if some has ended up dissipated as thermal energy of the surroundings.

Use in extended answers

Always close a 4- or 6-marker on energy with a sentence about conservation: "The total energy of the system is constant — none has been destroyed; some has been dissipated to the thermal store of the surroundings."

"Lost" Loses Marks. "Dissipated" Earns Them.

This is the single most-repeated piece of mark-scheme language in Topic 1. Use it every single time.

✗ Loses Marks

"Energy is lost."

Suggests energy disappeared — contradicts conservation.

✗ Loses Marks

"Energy is used up."

Same problem — implies the energy is gone.

✓ Earns Marks

"Energy is dissipated to the thermal store of the surroundings."

Uses the credited verb (dissipated). Names the destination store (thermal). Names where it ends up (surroundings). Three words doing three jobs.

When to use it

Anywhere energy ends up unhelpfully spread out — friction, drag, sound, heat from a wire, energy left in the brakes after a car stops. Dissipated, every time.

Examiner Alert

Jun 2024 Q1.2 — Energy Stores

The question asked which energy store increases. Examiners specifically rejected made-up names like "hydroelectric energy" and "movement energy", and required the word "potential" inside "gravitational potential".

Answers giving "kinetic energy" without the word store, or invented terms like "hydroelectric energy", lost the mark. The mark scheme accepted only the eight named stores. — AQA Examiner Report, Paper 1H, June 2024

The Lesson

If you're naming a store, the answer must come from the eight: kinetic, gravitational, elastic, thermal, chemical, magnetic, electrostatic, nuclear. Adding the word "store" is free insurance — write "kinetic store" not just "kinetic".

"Gravitational" vs "Gravitational Potential"

When the context is an object raised in a gravity field (water in a reservoir, ball at the top of an arc, weight on a shelf), use "gravitational potential" — that's the wording AQA credited in Jun 2024 Q1.2. "Gravitational" alone is sometimes accepted, but "potential" is safer and never wrong.

Framework — PEE for Describe Questions

Energy questions are usually descriptive — "describe", "explain", "state". The PEE framework structures them so every mark is hit.

Question

"A pendulum is pulled to one side and released. Describe the changes in energy stores during one full swing."3 marks

PPoint: Energy is transferred between the gravitational and kinetic stores.

EEvidence: At the highest point, the bob is momentarily stationary, so all the energy is in the gravitational store; at the lowest point, the bob moves fastest, so all the energy is in the kinetic store.

EExplain: A small amount of energy is also dissipated to the thermal store of the surroundings, because of air resistance and friction at the pivot — so the bob does not quite return to its original height.

Mark allocation

1 mark for naming both stores (P). 1 mark for the start/end positions linking to each store (E). 1 mark for mentioning dissipation to the thermal store of the surroundings (E).

Common Errors That Cost Marks

Students often writeCorrect version

"Energy is lost""Energy is dissipated to the thermal store of the surroundings"

"Heat energy of the water""Thermal store of the water" — heating is the process, thermal is the store

"Movement energy""Kinetic store"

"Hydroelectric energy""Gravitational store of the water" (hydroelectric is the resource)

"Energy is used up by the friction""Energy is transferred from the kinetic store to the thermal store by friction"

"Kinetic energy" (no word "store")"Kinetic store " — examiners flagged this in Jun 2024

Practice Question

A child compresses a spring inside a toy car and lets it go. The car shoots forward across the floor, gradually slowing until it stops.

Describe the main energy stores and transfers from the moment the spring is released until the car comes to rest. 4 marks

P

Point: Energy transfers from the elastic store of the compressed spring to the kinetic store of the car, and is then dissipated to the thermal store of the surroundings.

E

Evidence: When released, the spring exerts a force on the car and does work, transferring energy from the elastic store of the spring to the kinetic store of the car.

E

Explain: As the car moves, friction between the wheels and the floor — and air resistance — do work against the car's motion, transferring energy from the kinetic store of the car to the thermal store of the floor, the car, and the surrounding air.

+

Conservation: The total energy is constant — none has been destroyed; some has been dissipated to the thermal store of the surroundings, which is why the car eventually stops.

Checkpoint

✅ You can now

Define a system as an object or group of objects.

Name all 8 energy stores : kinetic, gravitational, elastic, thermal, chemical, magnetic, electrostatic, nuclear.

List the 4 transfer mechanisms : heating, work by force, work by current, radiation.

Describe energy changes for common situations using mark-scheme language — including the word dissipated .

State and apply the conservation of energy in a closed system.

Avoid the made-up store names ( movement, heat, hydroelectric, electrical ) that lose marks every year.

Coming Next

Lesson 1.02 — Calculating the energy in three of these stores: kinetic energy, gravitational potential energy, and elastic potential energy. We move from describing stores to putting numbers on them.

Summary

The Three Things to Remember

8 stores — kinetic, gravitational, elastic, thermal, chemical, magnetic, electrostatic, nuclear. Anything else is wrong.

4 transfers — heating, work by force, work by current, radiation.

Conservation — total energy is constant. Energy isn't lost; it's dissipated .

Mark-scheme phrases

"transferred from the [X] store to the [Y] store"

"by work done / by heating / by radiation"

"dissipated to the thermal store of the surroundings"

Phrases to avoid

"energy is lost / used up"

"heat energy" / "movement energy"

"hydroelectric energy" / "electrical energy" as stores

Exam Tip

For every energy answer, name both the start store and the end store, and say how the transfer happened (the mechanism). Three named items per change. That's where the marks live.