Energy Transfer By Heating

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Convection occurs in which states?
Liquids and gases
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When fluid is heated what happens to the density?
It decreases
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What is a convection current?
Warm fluid becomes less dense and rises which is then replaced by cooler, denser fluid
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What is convection?
Convection is the circulation of a fluid (liquid or gas) caused by heating it
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What is evaporation?
Evaporation is when a liquid turns in to a gas
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What is condensation?
Condensation is when a gas turns in to a liquid
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What can increase the rate of condensation?
Increased surface area or reducing surface temperature
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What can increase the rate of evaporation?
Increased surface area of liquid, increased temperature of the liquid, creating a draught of air across the liquid's surface
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The rate of energy transfer to or from an object depends on what 3 things?
the shape size and type of material, materials which are in contact with the object, the temperature difference between the object and its surroundings
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Three ways to maximise the rate of energy transfer to keep things cool?
Use things that are: good conductors, painted dull black, have maximum air flow around them
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Three ways to minimise the rate of energy transfer to keep things warm?
Use things that are: good insulators, white and shiny, prevent convection currents by trapping air in small pockets
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What is specific heat capacity?
Specific heat capacity of a substance is the amount of heat required to raise the temperature of 1kg of the substance by 1 degree celcius
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If an object has a greater mass, will its temperate increase faster or slower?
Slower
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What is the formula for specific heat capacity?
E = m x c x temp change
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How can you reduce the rate of energy transfer in our homes?
Fibreglass loft insulation, cavity wall insulation, double glazing, draught proofing, aluminium foil behind radiators
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What do U-Values tell us?
They tell us how much energy per second passes through different materials
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If the U-Value of an object is higher is it a good or bad insulator?
The lower the value the better the insulator
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Why are solar panels cheap to run?
They are cheap to run because they require no fuel to heat the water - only the suns energy
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What are disadvantages of solar panels?
Only work in the daytime, expensive to buy and install
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Which type of energy transfer is by electromagnetic waves?
Infra red radiation
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What prodperties of surfaces make them good absorbers of infra red radiation?
Dark, matt surfaces
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What properties of surfaces make them bad absorbers of infra red radiation?
Light, shiny surfaces
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Which materials are the best conductors?
Metals
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Why are materials such as wool and fibreglass poor conductors?
They contain air pockets which traps air and reduces the number of collisions between particles transferring energy
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Why are metals good conductors?
They are good because they have lots of free electrons which when heated gain kinetic energy and move through the metal
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Other cards in this set

Card 2

Front

When fluid is heated what happens to the density?

Back

It decreases

Card 3

Front

What is a convection current?

Back

Preview of the front of card 3

Card 4

Front

What is convection?

Back

Preview of the front of card 4

Card 5

Front

What is evaporation?

Back

Preview of the front of card 5
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