The transfer of heat energy is studied in GCSE Science. This is the fourth of eight quizzes on the topic and it looks specifically at the processes of conduction and convection.
Heat is thermal energy. It only ever travels in one direction - from warmer to cooler. You may have heard people say 'close the door to keep the cold out' but they really should be saying 'close the door to keep the warmth in'. Heat travels in 3 ways, but this quiz is concerned with only two of them - conduction and convection, which both involve the movement of particles.
Heat energy can move through any solid by conduction. Metals are usually good conductors of heat but liquids, gases and solids made mainly from non-metals are usually poor heat conductors. Poor conductors of heat are called 'insulators'.
Thermal energy is transferred from the hot end of a solid to the cold end. In metals, this process is very efficient because the particles are very closely packed and there are free electrons in the structure. In materials made mainly from non-metallic elements there are no free electrons and the atoms are fixed in place differently, so the heat doesn't get passed on as easily.
Heat is transferred through liquids and gases (fluids) by convection. The particles of fluids are free to change places. When heated, there is more kinetic energy in the particles so they move around more than they did before they were heated. Because they are moving faster, they are further apart which means there are fewer particles in each cm3 - the fluid is therefore less dense. As you know, less dense things float to the top in fluids. The heated part of the fluid rises to the top and cooler fluid moves in to take its place. This is called a convection current and, as it circulates, heat is spread through the entire fluid.
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