Last reviewed: 25 October 2026
Heat transfer is a favourite science topic because it explains so much of daily life: why a metal sufuria handle gets hot, why a room warms from a jiko and why we feel the sun’s warmth. This guide explains the three ways heat moves, gives everyday examples and describes the experiments learners need to know.
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Heat Always Moves From Hot to Cold
Heat is a form of energy. It flows from a hotter object or place to a cooler one until both reach the same temperature. A cup of tea cools because heat leaves it to the cooler air. Temperature, measured in degrees Celsius with a thermometer, tells us how hot something is.
Conduction
Conduction is the transfer of heat through a material, mainly solids, without the material itself moving. When one end of a metal spoon is placed in hot tea, the particles at that end vibrate faster and pass energy to their neighbours, so heat travels along the spoon.
- Good conductors: metals such as copper, aluminium and iron. Cooking pots are made of metal so heat reaches food quickly.
- Poor conductors (insulators): wood, plastic, cloth, air and wool. Pot handles are made of wood or plastic so they stay cool enough to hold.
Experiment: fix small pins with wax along rods of different metals, heat one end of each, and watch which pin drops first. The rod whose pin falls first is the best conductor.
Convection
Convection is heat transfer in liquids and gases (fluids) by the movement of the fluid itself. When part of a fluid is heated, it expands, becomes less dense and rises. Cooler, denser fluid sinks to take its place, setting up a convection current.
- Water in a sufuria heats all the way through because warm water rises from the bottom and cooler water sinks.
- Rooms have ventilators near the ceiling so warm, stale air can escape.
- Sea and land breezes at the coast are caused by convection currents in the air.
Experiment: drop a crystal of potassium permanganate at one side of a beaker of water and heat gently beneath it. The purple colour rises, moves across and sinks, showing the convection current.
Radiation
Radiation is heat transfer by waves (infrared radiation) that do not need a material to travel through. This is how heat from the sun crosses empty space to reach Earth, and how you feel warmth when sitting near a fire even though the air between is not doing the heating.
Surfaces matter. Dull, black surfaces are good absorbers and good emitters of radiation. Shiny, white or light surfaces reflect radiation and are poor absorbers. This is why light-coloured clothes keep you cooler in hot weather and why many roofs and water tanks in hot areas are painted in light colours.
All Three Together: The Thermos Flask
A vacuum flask keeps drinks hot or cold by reducing all three types of heat transfer. The vacuum between the double walls stops conduction and convection. The silvered inner surfaces reflect radiation back. The stopper, made of a poor conductor such as cork or plastic, reduces heat loss at the top.
Answering Exam Questions
When asked to explain an example, first name the method, then describe what happens to the particles or the fluid. “The handle stays cool because plastic is a poor conductor, so heat travels through it very slowly” earns more marks than “plastic does not get hot”.
Keep Practising
List five examples of each method from your own home, then test yourself. The Grade 8 Integrated Science papers include exam-style questions, and our electricity guide covers conductors and insulators. Use the exam countdown for five free daily questions and the What to Revise report to find gaps. Full papers with answers are in the Monthly Pass (KSh 500 by M-Pesa).