How does heat travel from a hot place to a cold place?
Describe the three ways heat is transferred (conduction, convection and radiation) and explain everyday examples of each
A practical answer to the N(T) Science point on heat transfer. The three ways heat travels, conduction, convection and radiation, with clear everyday examples and how to keep heat in or out.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
This dot point wants you to describe the three ways that heat travels from a hot place to a cooler place: conduction, convection and radiation. You should be able to explain how each one works in simple particle terms and give an everyday example of each. The big idea is that heat always moves from hotter to cooler, and it can travel in three different ways depending on the material it passes through, or even across empty space.
The answer
Heat always moves from hot to cold
Heat energy always flows from a hotter place to a cooler place. It keeps flowing until both places are at the same temperature. There are three ways this can happen.
Conduction
Conduction is how heat travels through solids, especially metals.
When one end of a solid is heated, the particles there gain energy and vibrate more. They knock into the particles next to them and pass the energy along, and those pass it on again, all the way through the solid. The particles themselves do not move along; they just pass the energy on like a chain.
Metals are good conductors: they pass heat along quickly. This is why a metal spoon in hot soup soon feels hot at the handle. Materials like plastic, wood, air and water are poor conductors, also called insulators, because they do not pass heat along well. This is why pan handles are made of plastic or wood.
Convection
Convection is how heat travels through liquids and gases (fluids).
When part of a liquid or gas is heated, it expands and becomes lighter (less dense), so it rises. Cooler, heavier fluid sinks to take its place, and then it gets heated in turn. This sets up a circulating flow called a convection current, which carries the heat around.
Convection is why warm air from a heater rises and spreads around a room, and why the water at the top of a kettle gets hot even though the heating element is at the bottom. Convection cannot happen in a solid, because the particles cannot flow.
Radiation
Radiation is how heat travels as invisible waves, called infrared radiation. It is the only way that does not need any particles, so it can travel through empty space.
This is how heat reaches us from the Sun across empty space, where there is no air to carry it. You also feel radiation when you stand near a fire or hold your hands toward a hot grill.
Dark, dull surfaces are good at giving out and taking in radiation, while light, shiny surfaces are poor at it and reflect radiation away. This is why shiny foil is wrapped around things to keep heat in or out.
Keeping heat in or out
To keep something warm, you slow down all three transfers: use insulators to stop conduction, trap air to stop convection, and use shiny surfaces to reflect radiation. A vacuum flask does all three, which is why it keeps a drink hot or cold for hours.
Examples in context
Example 1. A hot day in a parked car. A car left in the Sun gets very hot inside because heat from the Sun reaches it by radiation through the windows. People put a shiny silver sunshade on the windscreen because shiny surfaces reflect radiation away, keeping the car cooler.
Example 2. Cooking on a stove. When you heat a pot of water, the metal base conducts heat into the water (conduction), the heated water at the bottom rises and circulates to warm all the water (convection), and the glowing hot ring also sends out heat you can feel as radiation. All three transfers can happen at once in one everyday task.
Try this
Cue. Name the way heat travels through the metal base of a saucepan. Heat travels through the solid metal base by conduction.
Cue. Explain why a heater placed low in a room warms the whole room. The warm air rises by convection and cooler air sinks to replace it, setting up a current that carries heat around the room.
Cue. State why heat from the Sun reaches the Earth by radiation and not by conduction or convection. Space is empty, with no particles, and only radiation can travel without particles, so conduction and convection cannot work there.
Exam-style practice questions
Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Original4 marksA metal spoon is left standing in a cup of hot soup. After a while the top of the handle feels hot. (a) Name the way heat travels up the spoon. (b) Explain how this happens in the metal. (c) Suggest one material for the handle that would keep it cooler, and say why.Show worked answer →
(a) Heat travels up the spoon by conduction.
(b) The hot soup gives energy to the particles in the metal at the bottom. These particles vibrate more and pass the energy on to the next particles, and so on up the spoon, until the handle gets hot. Metal is a good conductor, so this happens quickly.
(c) A plastic or wooden handle would keep it cooler, because plastic and wood are poor conductors (insulators), so they do not pass the heat along easily.
What markers reward: naming conduction, describing particles passing energy along the metal, and choosing a poor conductor (plastic or wood) with the reason that it does not conduct heat well.
Original4 marksA room has a heater on the floor. (a) Name the way the warm air spreads around the room. (b) Explain why the warm air rises. (c) The Sun also warms the Earth. Name the way heat reaches us from the Sun, and state why it cannot be the same way as in part (a).Show worked answer →
(a) The warm air spreads by convection.
(b) When air is heated it expands and becomes lighter (less dense) than the cooler air around it, so the warm air rises. Cooler, heavier air sinks to take its place, setting up a circulating current.
(c) Heat reaches us from the Sun by radiation. It cannot be convection or conduction because there is no air (no particles) in the empty space between the Sun and the Earth, and radiation does not need particles to travel.
What markers reward: naming convection in the room, explaining warm air rising because it is less dense, naming radiation from the Sun, and saying radiation needs no particles so it crosses empty space.
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