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What is heat radiation?
The transfer of heat energy by IR radiation
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Does a hotter object have a higher or lower rate of emission of IR radiation?
higher
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Will an object that is hotter than its surroundings emit or absorb more IR radiation overall?
It will emit more than it will absorb
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What type of surface is good for reflecting IR radiation?
A light, shiney surface
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Describe a surface that would be poor at emitting IR radiation.
A light, shiney surface
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Explain, in terms of particles, why a solid melts when heated.
As a solid is heated, its particles gain energy and vibrate more. Eventually, the particles have enough energy to move past one another so the solid become a liquid.
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What is conduction?
The transfer of energy through a substance due to particle collisions. Particles in a subtance gain more kinetic energy and vibrate more, thus colliding with particles passing on energy through the substance.
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Explain why metals are good conductors.
They contain free electrons that are able to move through the metal, colliding with particles, passing on their energy further into the metal and not just in a fixed position, so energy is transferred more quickly.
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What is convection?
The transfer of heat by the movement of more energetic particles in a gas or liquid from a hotter to cooler region.
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In which state of matter does convection nor occur?
Solids - particles can only vibrate about a fixed position
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What is responsible for water vapour becoming visible steam?
Condensation
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In terms of particles, explain what happens when a gas condenses.
What a gas cools, the particles slow down, they lose kinetic energy and are closer together. When the temperature of the gas is cool enough, the particles clump together and become a liquid.
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What is evaporation?
Where a liquid becomes a gas.
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Give 4 ways you could increase the rate of evaporation of a liquid.
Increase temperature, decrease density, increase SA, increase air flow .... of liquid.
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Give 3 ways you could increase the rate of condensation of a gas.
Decrease temperature of gas, increase concentration of gas in air, allow gas to come in contact wil colder surface.
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The rate of energy transfer from an object depends on many factors. What are some of these factors?
SA, volume, material, the substance the object is in contact with.
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is the rate of energy transfer between an object and its surroundings higher or lower the bigger the temperature difference is between them?
Higher
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Arctic foxes have evolved small ears, with a small SA. How does this help?
It minimises heat loss by radiation to conserve body heat.
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Desert foxes have evolved large ears with a large SA. How does this help?
It allows them them to loss heat by radiation easily and keep cool.
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Explain how cavity wall insulation reduces energy loss.
Foam squirted into the gap between the bricks of a cavity wall stops convection currents being set up in the gap and reduces the amount of radiation in the gap.
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Explain how loft insulation reduces energy loss.
Helps reduce heat lose by convection.
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Explain how double glazing reduces energy loss.
The double layer of glass has an air gap in between so it conducts poorly and will reduce energery loss by conduction through the window
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What is the equation for payback time?
initial cost / annual saving
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What is U-value a measure of?
How insulating a material is.
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What is specific heat capacity?
The amount of energy needed to to change the temperature of 1kg of a material by 1°C.
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Do materials used in heaters usually have a low or high specific heat capacity?
High specific heat capacity so they can store large amounts of energy.
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What are the nine types of energy?
Elecrtical, light, sound, kinetic (movement), nuclear, thermal (heat), gravitational potential, elastic potential, chemical.
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What is the principle of conservation of energy?
Energy can be transferred usefully from one form to another, stored or dissipated but never created or destroyed.
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What does it mean for something to be efficient?
It means it wastes is very little of energy or power it's supplied with.
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Why is it not possible for a device o be 100% efficient?
some of the energy will always get wasted or lost, often by heat.
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What does the amount of energy transferred by an electrical appliance depend on?
Te power of the appliance and the amount of time it is switched on for.
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What units are usually used to measure the amount of electricity used in a home?
kilowatt-hours
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Describe 3 ways having no elecrticity can affect people's lives.
Affect convenience and safety - electrical lighting. Not as healthy - can't refridgerate food and vaccines. Communication - lack of internet and phones.
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Card 2

Front

Does a hotter object have a higher or lower rate of emission of IR radiation?

Back

higher

Card 3

Front

Will an object that is hotter than its surroundings emit or absorb more IR radiation overall?

Back

Preview of the front of card 3

Card 4

Front

What type of surface is good for reflecting IR radiation?

Back

Preview of the front of card 4

Card 5

Front

Describe a surface that would be poor at emitting IR radiation.

Back

Preview of the front of card 5
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