Physics (P1) Energy Transfer by Heating

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  • Created by: Roma
  • Created on: 12-12-13 20:38
What is infrared radation?
Energy transfer by electromagnetic waves which all objects emit it.
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How does heat affect the rate at which infrared radiation is emitted.
The hotter an object, the more infrared radiation it emits.
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What is a vacuum.
A region which doesn't contain anything (even particles).
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Which surfaces are good absorbers?
Dark, matt surfaces will get hotter quickest.
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Which surfaces are good emitters?
Dark, matt surfaces will transfer energy quickest.
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Which surfaces are good reflectors?
Light, shiny surfaces.
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What is the structure of a solid?
Particles are next to each other and vibrate in a fixed position so they have a fixed shape.
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What is the structure of a liquid?
Particles are in contact but can move at random. They don't have a fixed shaped so can flow.
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What is the structure of a gas?
Particles are far apart and move fast and at random. They can flow and have a high density.
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Where does conduction mainly occur?
Solids.
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How does conduction occur?
Particles at one end of a heated solid gain kinetic energy and vibrate more. This energy is passed on to neighbouring particles and so energy is transferred.
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Why are metals especially good conductors?
When heated, their free electrons gain kinetic electricity and move through the metal. They transfer energy by colliding with other particles.
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What are poor conductors called?
Isulators
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What materials are good insulators and how?
Materials such as wool and fibreglass because they contain trapped air.
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In what materials does convection occur?
Fluids (liquids and gases).
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How does convection occur?
As a fluid is heated, it expands, becoming less dense and rises. This warm fluid is replaces by cooler, less dense fluid. This produces a convection current which transfers energy throughout the liquid.
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Give an example of a small scale convection current?
Heating a beaker.
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Give an example of a large scale convection current?
Heating air above land - onshore and offshore breezes.
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What is evaporation?
A liquid turning into a gas.
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Why does evaporation occur?
The most energetic liquid molecules escape from the liquid's surface and enter the air. This decreases the average kinetic energy of the remaining molecules so the temperature also decreases. Evaporation therefore causes cooling.
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What factors increase the rate of evaporation?
Increases surface area, increases liquid temperature, creating a draught of air across the liquid.
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What is condensation?
A gas turning into a liquid.
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Where does condensation often occur?
Windows and mirrors.
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What factors increase the rate of condensation?
Increasing the surface area, and reducing the surface temperature.
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What affects the rate at which energy is transferred?
Temperature different between object and surroundings, the material the object is in contact with, the object's shape, the object's surface area.
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How can you minimise the rate of energy transfer by conduction, convection and radiation?
Use things that: are good insulators, are white and shiny, prevent convection by trapping air in small pockets.
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What is specific heat capacity?
The amount of energy requires to raise the temperature of 1 kilogram of the substance by 1 degree celsius. The greater the specific heat capacity, the more energy required for each degree temperature change.
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How does mass effect specific heat capacity?
The greater the mass of a substance being heated, the more energy required for each degree change.
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How can you reduce the energy transfer out of your home?
Fibreglass - reduce conduction, Cavity wall insulation - reduce convection, double glazing - reduce convection (through windows), Draught proofing - reduce convection, Aluminium foil behind radiators - reflect ifrared radiation back into the room.
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What is U-value?
A value given to a material which tells us how much energy per second passes through it. The lower the U-value the better the material.
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How do solar heating panels work?
They contain water heated by the Sun which could heat buildings or provide domestic hot water.
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Advantages and Disadvantages of solar heating panels?
They are cheap to run as no fuel is needed but are expensive to buy and install and don't run at night.
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Other cards in this set

Card 2

Front

How does heat affect the rate at which infrared radiation is emitted.

Back

The hotter an object, the more infrared radiation it emits.

Card 3

Front

What is a vacuum.

Back

Preview of the front of card 3

Card 4

Front

Which surfaces are good absorbers?

Back

Preview of the front of card 4

Card 5

Front

Which surfaces are good emitters?

Back

Preview of the front of card 5
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