P1 Energy transfer by heating

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  • Created by: KAustria
  • Created on: 11-06-14 14:08
How does temperature of an object affect the rate at which it emits infrared radiation?
The hotter the object the more infrared radiation is being emitted
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Explain why we receive infrared radiation form the sun?
Infrared radiation is an electromagnetic wave which means that it is able to travel through a vacuum.
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What surfaces are good absorbers of infrared radiation?
Dark, matt surfaces.
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Why are houses in hot countries often painted in white?
So that they do not absorb as much infrared radiation.
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Are dark, matt surfaces good emitters? Explain
Yes. This mean that is it is painted dull black it will transfer and cool down energy more quickly than the same object painted in shiny white.
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What surfaces are goof reflectors of infrared radiation?
Shiny, light surfaces
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What are the 3 states of matter?
Solids, liquids and gases/
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How is the arrangement of the particles ina liquid different fromt hat in a solid?
They are in contact with each other however they are able to move randomly so it doesn't have a fxed shape and canf low
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How is an arrangement of the particles in a gas different from that ina liquid?
They are further apart and move at random much faster, so a gas doesn't have a fixed shape and can flow.
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What 2 states are poor conductors?
Liquids and gases
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How is energy conducted through a solid?
If one end of a solid is ehated, the particles at that end gain kinetic energy and vibrate more. This energy is passed to neighbouring particles and int his way the energy is transferred though the solid.
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Describe conduction in metals
When metals are heated thier free elctrons gain kinetic energy and move through the metal, transferring energy by colliding with other particles.
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What are insulators?
Poor conductors
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why are wools and fibreglass good insulators?
Because they contain trapped air.
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In what states does convection occur?
this occurs in fluids. - Liquids and gases
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Explain how a convection current is formed
When a fluid is heated. it expands and becomes less dense, therefore it rises. The warm fluid is replaced by the cooler, denser fluid. Resulting to a convectio current which transfers energy throughout the fluid.
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What is evapouration?
This is when a liquid turns into a gas.
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Why does evapouration occur?
The most energetic liquid molecules escape from the liquid's surface and enter the air. Therefore the avg kinetic energy is less so the temperature decreases. Evap causes cooling
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What are the 3 ways you can increase evaporation?
1. increasing surface area os liquid 2. increasing temperature of fluid 3. Creating a draught of air across the the liquid's surface.
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What is condensation?
When a gas turns into a liquid. This normally takes place in cold surfaces such as windows and mirrors.
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How do yo increase the rate of condensation?
1. increasing the surface area 2. reducting the surface temeprature
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How do you increase the rate of energy transfer?
Greater temperature gradient.
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What are the 3 othe factors wich depend on the rate of energy transfer?
1. The material the object is in contact to 2. the object's shape 3. The objects surface area.
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How can you maximise the rate of energy transfer to keep things cool?
1. Use good conductors 2. pain things dull black 3. have air flow maximised.
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How do you minimise the rate of energy transfer to keep things wamr?
1. Use good insulators 2. White and shiny surface 3. Prevent convection currents by trapping air in small pockets.
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What is specific heat capacity?
The amount of energy requirs to raise the temperature of 1 kilogram of the substance by 1 degree celsius.
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The greater the specific heat capacity, the ___ energy required for each degree temperature to change.
more
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The greater the mass of the substance the ___ energy requird for each degree temperature change
more
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What are the 5 measures to minimise the rate of energy transfer?
1. fibreglass loft insulation ( conduction) 2. Cavity Wall insulation (convection) 3. Double glazing (conduction) 4. Draught proofing (convection) 5. Aluminium foil behind radiators (infrared radiation)
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What are U valus?
The value which tells you how much energy per second passes through a amterial.
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How do you know if a material is a better insulator?
The lower the U value the better the insulator.
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Other cards in this set

Card 2

Front

Explain why we receive infrared radiation form the sun?

Back

Infrared radiation is an electromagnetic wave which means that it is able to travel through a vacuum.

Card 3

Front

What surfaces are good absorbers of infrared radiation?

Back

Preview of the front of card 3

Card 4

Front

Why are houses in hot countries often painted in white?

Back

Preview of the front of card 4

Card 5

Front

Are dark, matt surfaces good emitters? Explain

Back

Preview of the front of card 5
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