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Chapter 6 Section 2
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Conduction and Convection
There are many ways to transfer thermal energy. Conduction which is the transfer of thermal energy by collisions between particles in matter. The rate of conduction of a material depends on its specific heat. Ex: holding an ice cube. Convection is the transfer of thermal energy by the movement of warmer and cooler fluid from place to place. Ex: lava lamp
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Convection currents are also responsible for weather and biomes on earth.
The equator gets more direct sunlight than the poles. This makes the equator warmer than the poles. That warm air then moves to the cooler air at the poles. This makes the area at the equator more moist more water and the air closer to the poles more desert like.
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Radiation A third type of transfer is radiation.
Radiation is the transfer of energy by electromagnetic waves. Usually it is referred to a radiant energy. An example of this would be warming your self by fire.
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Radiant Energy and Matter
When radiation strikes a material, some of the energy is absorbed, some is reflected, and some may be transmitted through the material. The amount of energy absorbed, reflected, or transmitted depends on the type of material. Light colored things will reflect more than dark colored things.
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Radiation in Solids, Liquids, and Gases
Radiant energy can travel between the molecules. This allows the molecules to absorb some of the energy and radiate it back off. It is easier to absorb energy in gases as their particles are spaced farther apart. This makes gases the more important material for radiant energy. Ex: the atmosphere.
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EM Spectrum This type of radiant energy shouldn’t be confused with nuclear radiation.
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Controlling Heat Flow All living organisms control heat flow to some degree. When you are cold you put on a jacket. Seal and whales have blubber to prevent heat loss. Lizards have scaly light colored skin to prevent loss of moister and reflect sunlight to prevent it from over heating.
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These are all examples of insulators.
An insulator is a material in which heat flows slowly. It can work to keep heat out or in. Gases such as air work much better as insulators.
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Thermos
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Section Check How are conduction and convection different?
Why do you think penguins have black feathers? What are two animal adaptations that controls the flow of heat? Why does trapped air make a material like fleece a good insulator?
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