Conduction, convection, and radiation
Describe and compare the three mechanisms of heat transfer — conduction (particle vibration through solids), convection (fluid movement in liquids/gases), and radiation (infrared waves) — and explain that the rate of transfer depends on temperature difference
What a learner can do afterwards
- Explains the particle-level mechanism for conduction and why metals are good conductors
- Describes a convection current using particle theory and gives a real-world example
- Explains that all objects emit and absorb infrared radiation and how surface colour affects this
- States that a greater temperature difference increases the rate of heat transfer
The lesson
You already know that matter is made of tiny particles that are always moving, and that energy can move from place to place. Heat energy moves between objects in three different ways: conduction, convection, and radiation. Which way happens depends on what the heat is moving through.
Picture a pot of soup heating on a hob. The particles at the bottom heat up first and spread further apart, so that part of the soup becomes less dense and rises. Cooler, denser soup sinks to take its place, gets heated, and rises too. This loop is a convection current, and it carries heat right through the soup, not just at the bottom.
Radiation is different because it does not need particles at all. Every object gives off infrared radiation, and every object absorbs some too. That is how heat crosses the empty space between the Sun and Earth. Dark, matt surfaces absorb and emit infrared radiation well, while light, shiny surfaces reflect most of it away.
The bigger the temperature difference between two objects, the faster heat transfers between them. A radiator warms your hands quickly when it is much hotter than the room, but the transfer slows down as your hands warm up and the difference shrinks.
Conduction moves heat through touching particles, convection moves heat through a moving fluid, and radiation moves heat through waves that need no particles at all, and all three speed up as the temperature difference grows.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.