GCSE Physics revision

Energy transfers in a system

Conservation and dissipation of energy

AQA 4.1.2.1

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AQA student objectives

Learning pathway

ALL 🎯

Describe with examples where there are energy transfers in a closed system, that there is no net change to the total energy.

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Apply the scientific explanation of energy transfers in a system to a relevant example.

SOME 🎯🎯🎯

Analyse a new situation involving energy transfers in a system and explain the scientific reasoning.

Revision summary

Read on screen, then print for Cornell-style active revision.

Heat energy can be transferred by three main processes: conduction, convection, and radiation.
Conduction and convection both rely on particles to transfer energy, whereas radiation does not require any particles at all.

Conduction is the transfer of heat energy through collisions between neighbouring vibrating particles.
When one end of a solid is heated, particles gain kinetic energy and vibrate more, colliding with neighbouring particles and passing on energy along the material.
Conduction occurs mainly in solids because particles are closely packed together, making collisions more frequent and energy transfer more efficient.
In liquids and gases, particles are further apart, so collisions are less frequent and conduction is less effective.

2. Conduction: Heat Transfer Through SolidsAQA

Conduction is the transfer of heat energy through collisions between neighbouring vibrating particles.
When one end of a solid is heated, particles gain kinetic energy and vibrate more, colliding with neighbouring particles and passing on energy along the material.
Conduction occurs mainly in solids because particles are closely packed together, making collisions more frequent and energy transfer more efficient.
In liquids and gases, particles are further apart, so collisions are less frequent and conduction is less effective.

Thermal conductivity describes how well a material conducts heat — materials with high thermal conductivity transfer heat quickly.
Metals such as copper and aluminium have high thermal conductivity, making them good conductors of heat.
Non-metals such as wood and plastic, as well as fluids like air and water, have low thermal conductivity and are referred to as insulators.
Insulators are useful in everyday life — for example, a plastic sleeve on a mug slows heat loss and prevents burns when holding a hot drink.

3. Thermal Conductivity and InsulatorsAQA

Thermal conductivity describes how well a material conducts heat — materials with high thermal conductivity transfer heat quickly.
Metals such as copper and aluminium have high thermal conductivity, making them good conductors of heat.
Non-metals such as wood and plastic, as well as fluids like air and water, have low thermal conductivity and are referred to as insulators.
Insulators are useful in everyday life — for example, a plastic sleeve on a mug slows heat loss and prevents burns when holding a hot drink.

Convection is the transfer of heat energy by particles that move from place to place, and it occurs mainly in fluids (liquids and gases).
When a fluid is heated, its particles gain kinetic energy, move faster, and spread apart, making the heated fluid less dense.
The less dense, warmer fluid rises above the cooler, denser fluid, which sinks to take its place.
This continuous cycle of rising warm fluid and sinking cool fluid creates a convection current.
A common example is heating water in a pot, where warm water rises from the bottom and cooler water moves down to replace it.

4. Convection: Heat Transfer Through FluidsAQA

Convection is the transfer of heat energy by particles that move from place to place, and it occurs mainly in fluids (liquids and gases).
When a fluid is heated, its particles gain kinetic energy, move faster, and spread apart, making the heated fluid less dense.
The less dense, warmer fluid rises above the cooler, denser fluid, which sinks to take its place.
This continuous cycle of rising warm fluid and sinking cool fluid creates a convection current.
A common example is heating water in a pot, where warm water rises from the bottom and cooler water moves down to replace it.

Radiation is the transfer of heat energy by infrared waves, which do not require particles and can travel through a vacuum.
This is how heat energy from the Sun reaches the Earth, travelling through the vacuum of space.
All objects, regardless of temperature, both emit and absorb infrared radiation at all times.
Hotter objects emit more infrared radiation than cooler objects — for example, a hot mug of coffee emits more radiation than a cold one.

5. Radiation: Heat Transfer Without ParticlesAQA

Radiation is the transfer of heat energy by infrared waves, which do not require particles and can travel through a vacuum.
This is how heat energy from the Sun reaches the Earth, travelling through the vacuum of space.
All objects, regardless of temperature, both emit and absorb infrared radiation at all times.
Hotter objects emit more infrared radiation than cooler objects — for example, a hot mug of coffee emits more radiation than a cold one.

Conduction transfers heat through particle collisions and is most effective in solids with closely packed particles.
Convection transfers heat through the bulk movement of fluid particles and relies on density differences caused by temperature changes.
Radiation transfers heat via infrared waves and is the only method that does not require a medium (particles) to travel through.

6. Comparing the Three MethodsAQA

Conduction transfers heat through particle collisions and is most effective in solids with closely packed particles.
Convection transfers heat through the bulk movement of fluid particles and relies on density differences caused by temperature changes.
Radiation transfers heat via infrared waves and is the only method that does not require a medium (particles) to travel through.