Science Unit 1

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  • Created by: Charlotte
  • Created on: 12-05-14 18:30
How is heat radiation used in grilling and toasting?
Grills and toaster heat food by infrared (heat) radiation. The heat radiated by the grill is absorbed by the surface particles of the food, increasing their kinetic energy. the heat energy is then conducted or convected to more central parts.
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Why do people line their grill pan with foil?
The foil reflects the heat radiation back on to the bottom of the food being grilled, so the food is cooked more evenly.
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How do microwaves use radiation to cook food?
Microwaves use electromagnetic waves that have a different wavelength to infrared. Microwaves penetrate about 1 cm into the outer layer of food where they're absorbed by water or fat molecules, increasing their kinetic energy. conduction/convection.
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What are thing that emit energy called?
sources
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what are things that transfer and waste/lose energy called?
sinks
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How do you save energy in your home?
you can insulate your home so the sinks 'drain' less. eg. curtains. you can also make sources and sinks more efficient, so they waste less energy
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what is payback time?
it cost mnoey to buy and intall insulation/ more efficient appliances but it saves you money as your energy bills are lower. the money you've saved on energy bills will equal the initial cost- the time it takes is the payback time.
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What is Loft insulation?
fibreglass 'wool' laid across the loft floor reduces conduction through the ceiling into the roof space.
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What is cavity walls& insulation?
two layers of bricks with a gap between the reduce conduction but you still get some energy lost by convection. Squirting insulating foam into the gap traps pocket of air to minimise convection.
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What is draught-proofing?
Strips of foam and plastc around doors and windows stop hot air going out-reducing convection
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What is double glazing?
two layers of glass with an air gap between reduce conduction.
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what is a thermogram?
A thermogram displays different temperature as different colours. Hot parts show as white, yellow, red and colder parts are black, darkblue and purple. if it looks hot is is losing heat.
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#why are useful machines useful?
because they convert energy from one form to another. eg. cars, you put in a chemical energy and the engine converts it into kinetic energy.
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Is all of the output energy useful?
No, the total energy output is always the same as the enery input, but only some of the energy is useful. for every joule of energy, only a fraction is converted in to useful energy as some is lost as heat. the less energy wasted, the more efficient.
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What is a sankey diagram?
they are enrgy transformation diagrams - easy to see at glance the input energy and how much is useful and how much is wasted.
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What do the thickeness of the arrows on a sankey diagram show?
the thicker the arrow, the more energy it represents.
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Other cards in this set

Card 2

Front

Why do people line their grill pan with foil?

Back

The foil reflects the heat radiation back on to the bottom of the food being grilled, so the food is cooked more evenly.

Card 3

Front

How do microwaves use radiation to cook food?

Back

Preview of the front of card 3

Card 4

Front

What are thing that emit energy called?

Back

Preview of the front of card 4

Card 5

Front

what are things that transfer and waste/lose energy called?

Back

Preview of the front of card 5
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