# Boardworks BTEC First Applied Science Types of Energy

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Boardworks BTEC First Applied Science Types of Energy
Unit 2: Energy and Our Universe

Boardworks BTEC First Applied Science
What is thermal energy? Boardworks BTEC First Applied Science Types of Energy Heat is a type of energy called thermal energy. Heat can be transferred (moved) by three main processes: conduction, convection and radiation. What happens to hot cup of tea in a cool room? What happens to a cold ice lolly on a warm day? What do these examples tell you about heat transfer? Teacher notes Hot tea cools down in a warm room and a cold ice lolly warms up (and melts) on a warm day. These are both examples of thermal energy moving from a warmer area to a cooler area. Heat energy only flows when there is a temperature difference between a warmer area and a cooler area. During heat transfer, thermal energy always moves in the same direction: HOT COLD

Boardworks BTEC First Applied Science
What is conduction? Boardworks BTEC First Applied Science Types of Energy When you touch something hot, the heat is transferred to your hand by conduction. Conduction is the transfer of heat energy between neighbouring particles by their vibration. Would you expect conduction to be most effective in solids, liquids or gases? Teacher notes The answers to the questions on this slide are considered on the next slide. To help them answer the second question, students could be encouraged to think about touching a hot metal object compared with touching a hot plastic object. Is conduction more effective in metals or plastics? 3

Where is conduction most effective?
Boardworks BTEC First Applied Science Types of Energy Conduction is more effective in solids than liquids or gases due to the arrangement of particles. In solids, they are very close together and ordered and so easily transmit energy from one to another by vibration. solid liquid gas Teacher notes Students could be asked to discuss the limitations of the visual representations of solids, liquids and gases, which include: the models are static whereas the particles are actually moving the models are two-dimensional whereas the particles are actually 3-dimensional. Students could also be asked to discuss the good points of the models and why they are useful. It should be noted that the diagram of a metal is not drawn to scale. It should be stressed to students that an electron is tiny compared to a metal ion, especially the nucleus. This means that the electrons are able to pass between the metal ions. For animations showing thermal conduction in a metal and a non-metal, see the Unit 1 presentation Investigating Physical Properties. Metals are better conductors than plastics because they have free electrons that move through the metal, transferring the thermal energy. metal ion free electron

Boardworks BTEC First Applied Science
What is convection? Boardworks BTEC First Applied Science Types of Energy Liquids and gases can both flow and behave in similar ways, so they are called fluids. When fluids are heated, the particles move around more and spread out. Warmer regions of a fluid are therefore less dense than cooler regions. The warmer regions will rise because they are less dense. The cooler regions will sink as they are more dense. Teacher notes The diagram illustrates how temperature affects the density of particles in a fluid. When using the diagram it should be highlighted that the particles near the top are further apart and the particles near the bottom are closer together. The widely-spaced particles at the top of the diagram represent a warmer region of the fluid. They are floating on top of a cooler region (represented by the particles spaced closely together) because the warm region of the fluid is less dense. It should be noted that the density of the regions of the fluid in this diagram have been exaggerated to increase the contrast and make the regions clearer to see. This is how heat transfer takes place in fluids and is called convection.

Boardworks BTEC First Applied Science
Convection currents Boardworks BTEC First Applied Science Types of Energy Teacher notes This three-stage animation uses the example of boiling water in an electric kettle to demonstrate how convection occurs in a liquid. Whilst showing the animation it could be highlighted that the hot water rises up through the cold water because the hot water is less dense. The denser cold water falls below the hot water, pushing the hot water up.

Boardworks BTEC First Applied Science Types of Energy Confusingly, radiators mainly transfer heat by convection, although they do also transfer some heat by radiation. Warm air from the radiator rises, setting up a convection current in the room. 7

Boardworks BTEC First Applied Science Types of Energy The Earth is warmed by heat energy from the Sun. How does this heat energy travel from the Sun to the Earth? infrared waves There are no particles between the Sun and the Earth, so the heat cannot travel by conduction or by convection. The heat travels to Earth by infrared waves. These are similar to light waves and are able to travel through empty space. Infrared waves heat up objects that absorb them, and are also known as thermal radiation. 8

Investigating thermal emission
Boardworks BTEC First Applied Science Types of Energy Teacher notes This virtual experiment uses a Leslie’s cube to investigate the emission of heat radiation from different surfaces. It could be used as a precursor to running the practical in the lab or as a revision exercise. When using this activity, it should be made clear that the water inside the cube and the initial temperature of each side is the same in each experiment. The thermopile measures the amount of heat radiation emitted by the surface, which is then recorded in the table. A black kettle would cool down faster than a shiny metallic kettle because black objects are better emitters of thermal radiation. Which type of kettle would cool down faster: a black kettle or a shiny metallic kettle? 9