What heat transfers involve the the transfer of energy by particles?
Conduction and convection.
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What is the main form of heat transfer in solids?
Conduction.
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What is the main form of heat transfer in liquids?
Convection
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What is the main form of heat transfer in gases?
Infrared Radiation.
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How can infrared radiation be emitted?
Through solids, liquids and gases.
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Whether or not conduction or convection are taking place, can any object both absorb and emit infrared radiation?
Yes they can.
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If an object is hotter than it's surroundings, does it emit more radiation than it absorbs?
Yes it does
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What type of surfaces absorb infrared radiation well?
Dark, matte surfaces.
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What type of surfaces absorb infrared radiation poorly?
Light, shiny surfaces.
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What are the three states of matter?
Solids, liquids and gases.
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Conduction of heat occurs mainly in what?
Solids.
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Metals are good conductors because of what?
Because of their free electrons.
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Why is conduction faster and denser in solids?
Because the particles are closer together and so will collide more often and pass energy between them.
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When you heat a substance, you give its particles more what?
Kinetic energy.
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Metals conduct so well because what?
Because the electrons are free to move inside the metal.
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What two states of matter does convection happen in?
Liquids and gases.
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Convection occurs when what happens?
When the more energetic particles move from the hotter region to the colder region and take their heat energy with them.
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Convection can't happen in solids, why?
Because the particles can't move.
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Convection currents are all about what?
Changes in density.
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What happens in a room with a radiator?
The hot air from the radiator rises, the warm air then displaces the cold air at the top of the room, the cool, denser air falls and the cool air flows to fill the gap left by the rising, heated air.
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What happens in condensation?
When a gas turns to a liquid.
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When a gas cools, the particles in the gas slow down and lose what?
Kinetic energy.
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What happens in evapouration?
When a liquid turns to a gas.
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Evapouration is when...
Particles escape from a liquid.
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The bigger the surface area of an object, the more _______ that can be emitted from (or absorbed by) the surface - so the quicker the transfer of heat.
Infrared waves.
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If a flask is double walled with a vacuum between the two walls, what does this do?
It stops all the conduction and convection through the sides.
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Why are the walls of a flask silvered?
To keep heat loss by radiation to a minimum.
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Why is a flask supported using insulating foam?
Because this minimises heat conduction to or from the outer flask.
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Why is the stopper made of plastic and filled with cork or foam?
To reduce any heat conduction through it.
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What is cavity wall insulation?
When foam is squirted into the gap between the bricks as this reduces convection and radiation across the gap.
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What is loft insulation?
When a thick layer of fibre glass wool is laid out across loft floor and ceiling to reduce heat loss from the house by conduction and convection.
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What is a hot water tank jacket?
It is a lagging such as fibreglass wool that reduces conduction and radiation.
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What do thick curtains do?
Bit bits of cloth go over the window to reduce heat loss by conduction and radiation.
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What do U-Values do?
They show how fast heat can transfer through a material.
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Other cards in this set
Card 2
Front
What heat transfers involve the the transfer of energy by particles?
Back
Conduction and convection.
Card 3
Front
What is the main form of heat transfer in solids?
Back
Card 4
Front
What is the main form of heat transfer in liquids?
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