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Turkboy Jr

on 15 September 2012

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Transcript of JR

Part 4
Heat in the Environment By: Eren. Ertas Subject: Science
Class: 7a How is heat transmitted
through Conduction, Convection, and Radiation? Question How heat is transmitted through
Conduction? Conduction is the transfer of heat between substances that are in direct contact with each other. The better the conductor, the more rapidly heat will be transferred. Metal is a good conduction of heat. Conduction occurs when a substance is heated, particles will gain more energy, and vibrate more. These molecules then bump into their neighbours and transfer some of their energy to them. This then continues and passes the energy from the hot end down to the colder end of the substance. Some good conductors are: Copper, Silver, Iron, and Steel and some bad conductors are: Wood, Styrofoam, Paper, and Air. Two objects must be touching for this transfer to occur. Heat energy can move through a substance by conduction. Metals are good conductors of heat, but non-metals and gases are usually poor conductors of heat. Poor conductors of heat are called insulators. Heat energy is conducted from the hot end of an object to the cold end. The electrons in piece of metal can leave their atoms and move about in the metal as free electrons. The parts of the metal atoms left behind are now charged metal ions. The ions are packed closely together and they vibrate continually. The hotter the metal, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons. These move through the structure of the metal, colliding with ions as they go. ( Here is a video of how heat is
transmitted through Conduction.) ( Here is a video of how heat is transmitted through Convection.) How is heat transmitted through
Convection? Convection is the up and down movement of gases and liquids caused by transfer heat. As a gas or a liquid is heated, it warms, expands, and rises because it is less dense. When the gas or liquid cools, it becomes denser and falls. As the gas or liquid warms and rises, or cools and falls, it creates a cenvection current. Convection is the primary method by which heat moves through gases and liquids. Convection is the concerted, collective movement of ensembles of molecules within fluids (i.e. liquids, gases) and rheids. Convection of mass cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids. Diffusion of heat can take place in solids, but is referred to separately in that case as heat conduction. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection. Liquids and gases expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size. How is heat transmitted through
Radiation? Radiation is energy transmitted directly through space. Although it does not require matter in transmission, it does require a line of sight connection between the objects.
All objects radiate energy or heat, which heats all cooler objects around it. Solar radiation passes through space to heat (and light) objects that it strikes. A person in a room with cold windows will radiate heat to the windows and that person will feel cool even if the air in the room is warm. If the window is covered, the sight connection is broken and that person will no longer feel cool. Radiation is a method of heat transfer that does not rely upon any contact between the heat source and the heated object as is the case with conduction and convection. Heat can be transmitted though empty space by thermal radiation often called infrared radiation. This is a type electromagnetic radiation . No mass is exchanged and no medium is required in the process of radiation. Examples of radiation is the heat from the sun, or heat released from the filament of a light bulb. ( Here is a video about how heat is transmitted through Radiation.) Thank you for watching! :) Hope you enjoyed everything and learned some information on how heat is transmitted through Conduction, Convection, and Radiation. ( Here is a picture as a example for Conduction.) ( Here are 2 pictures showing how heat is transmitted through Convection.) (Here are 2 pictures of Conduction, Convection, and Radiation.) (Here is another picture of Conduction, Convection, and Radiation.) ( This is a picture showing how heat is transmitted through Radiation.) (Conduction, Convection, and Radiation.)
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