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15 Cards in this Set
- Front
- Back
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How does thermal energy flow? |
Thermal energy flows from a region of higher temperature to a region of lower temperature |
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What is conduction? |
Conduction is the transfer of thermal energy through a medium without any flow of the medium |
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Why are solids better conductors of thermal energy than liquids and gases? |
Molecules are packed closer together in solids than in liquids and gases, thus there are more frequent collisions between the particles and so, kinetic energy can be transferred more quickly. |
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How does conduction work in non metals? |
1) When one part of the solid is heated, the atoms there gain kinetic energy and vibrate faster. 2) These atoms collide with their less energetic neighbours, resulting in a transfer of kinetic energy from the hotter area to the colder area. 3) This process continues until all the particles possess the same amount of thermal energy. |
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Why is conduction better in metals? |
Conduction is far better in metals than non-metals due collision of vibrating atoms & the movement of free electrons. |
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How does conduction work in metals? |
When heated, the free mobile electrons gain energy and move faster. Since free electrons are free to travel in the spaces between the atoms to transfer energy, conduction occurs much faster in metals. |
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Why are metals good thermal conductors? |
Free electrons are free to move from a hotter region to a cooler region, resulting in thermal energy from being transferred |
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Why are metals good electrical conductors? |
Free electrons are free to diffuse from a point of higher potential to a region of low potential, resulting in electric current flowing through them |
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What is convection? |
Convection is the transfer of thermal energy by means of convection currents in a fluid or gas due to a difference in density |
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Why is a convection current set up in convection? |
Due to difference in densities of water in different regions |
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Why is it not possible for solids to undergo convection? |
Convection involves the bulk movement of the fluid that carries the thermal energy which is not possible in solids |
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How does convection work in a liquid? |
1) When part of a liquid is heated, it expands in volume, becoming less dense than the surrounding liquid and rises. 2) The cooler and denser liquid sinks. The cooler liquid in turn gets heated up and rises, resulting in a continuous convection current. |
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How does convection work in a gas? |
1) The hot air near the heat source rises as it expands and becomes less dense, while the cooler and denser air at the top sinks. 2) The cooler air now gets heated up and rises, resulting in a continuous convection current. |
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What is radiation? |
Radiation is the transfer of thermal energy in the form of electromagnetic waves without the aid of a medium |
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What are the factors affecting radiation? |
- Surface temperature(The hotter an object, the higher the rate of energy emission.) - Surface area(The larger the surface area, the higher the rate of energy transfer.) - Surface colour & temperature (Rough, dull black surface is a better emitter and absorber of infrared radiation.) |
