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  • Created by: apple87
  • Created on: 16-04-14 14:55
What happens when a substance is heated?
It gains kinetic energy
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What causes substances to change their state?
The kinetic energy makes the particles move around faster, in a solid the particles vibrate more rapidly.
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What is an absolute scale?
A scale that can't go lower than zero, energy is measured on an absolute scale because there is a limit to how slow particles can move.
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In what direction does energy flow?
From hot objects to colder objects- if there is a diference in temperature between two places energy will flow between them.
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What is specific heat capacity?
The amount of energy it takes to heat 1 kg of something by 1 degree.
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What is happening when a substance is melting or boiling?
The temperature doesn't increase because the energy is being used to break the intermolecular bonds.
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What happens when a substance is condensing or freezing?
Bonds are forming between particles this releases energy, this means the temperature doesn't go down.
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What is specific latent heat?
The amount of energy needed to melt 1kg of material without changing its temperature.
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What is the conduction of heat?
The process where vibrating particles pass on extra kinetic energy to neighbouring particles.
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Why does metal conduct heat really well?
Some of their electrons are free to move inside the metal, heating the electrons makes the electrons move faster and colide with other free electrons transferring energy.
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How does convection works?
The warmer less dense fluid rises above its colder denser sourroundings. As the warm air rises cooler flud takes its place. As this process continues you get a circulation of fluid, convection currents. This is how immersion heaters work.
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When does convection occur?
When the energetic particles move from the hotter region to the cooler region and take their heat energy with them.
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Why does a tile floor feel warmer than carpet?
The tile conduct heat way from your feet quicker
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What sort of wave is heat radiated as?
Infrared
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Why is radiation different from convection and conduction?
It doesn't need a medium to travel through it can only occur through transparent substances like air, water and glass. The amount of radiation emitted or absorbed depends on its surface colour or texture.
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Al objects emit and absorb...
heat radiation.
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What kind of surfaces are good at absorbing and emitting.
Matt black surfaces
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What kind of surfaces are poor absorbers and emitters?
Light coloured, smooth, shiny surfaces.
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How is heat radiation used in cooking?
Grills and toasters emit infrared radiation which is absorbed by surface particles of the foo, the heat energy is convected or conducted to other parts of the food.
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What are things that emit energy called?
Sources
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What are things that transfer and waste or lose energy called?
Sinks
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How do you work out payback time?
initial cost/annual saving.
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What does a termogram do?
It show where your house is leaking heat.
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What is the amplitude?
The displacment from the rest position to the crest, (not from crest to trough)
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What is the wave length?
The length of a full cycle of the wave, eg from crest to crest.
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What is the frequency?
The number of complete cycles or oscillations passing a certian point per second. Frequency is measured in hertz 1 herts is one wave a second.
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Angle of incidence=...
Angle of refraction
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If the angle of incidence is less than the critical angle...
most of the light is refracted into the outer layer but some of it is internally reflected.
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If the angle of incidence is equal to the critical angle...
the ray would go along the surface of with quite a bit of internal reflection as well.
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If the angle of incidence is greater than the critical angle...
no light comes out its all internally refelcted- total interanl reflection.
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What happens when waves pass though a gap?
Diffraction occurs
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What does the amount of diffraction depend on?
The size of the gap reletive to the wave length. The narrower the gape or the longer the wavelength the more the waves spread out.
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What is refraction?
Changing the speed of a wave and changing the direction
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Whn does refraction happen?
When the waves meet a new medium at an angle.
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What happens if the wave hits the boundary face on?
The wave slows down but doesn't change direction, it now has a shorter wavelength but the same frequency.
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What happens when a a wave meets a different medium at an angle?
Part of the wave hits the dense layer first and slows down, while anouther part carries on a a faster speed for a while. This make the wave change direction it has been refracted.
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What do the properties of EM waves depend on?
Frequency and wave length
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The EM waves at the ends of the spectrum are able to ...
pass through material.
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Why are x rays dangerous?
The have a higher frequency which gives them more energy, this can also lead to ionisation.
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What is ionisation?
What atoms lose or gain electrons.
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What are the advantages of using light signals?
Travels really fast, can carry ots of informationvery quickly, multiplexing.. Information is fairly secure the wires can't be tapped into. As it is digital ther is lttile interference
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What are the problems with wireless neworks?
The signals can be intercepted, relieson being able to get a signal
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What are the problems with communication with cables?
They can be difficult to repair
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What are the advantages with wireless communication?
No cables to repair and it is portable eg mobile phones, laptop wifi
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How do optic fibres work?
They work by bouncing waves of a very narrrow core which is protected by outer layers. The ray of light enters the fibre at an angle grater than the critical angle for the material this causes total internal reflection.
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What are optical fibres used for?
Telephone, broadband internet cables. Medical purposes to see inside the body.
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What is monochromatic light?
All the light is in phase, all in one single pure colour. All the troughs and crests match. This makes a more intense beam.
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Is ordinary ligh in or out of phase?
Out of phase
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Do lasers have high or low divergence?
Low divergence
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How do CDs work?
made up of billions of shallow pits, area between the pits is called land. A laser is reflected off the CD, it refelcts of the pits and lands slightly differently, the difference is picked up by a light sensor, the signal changes to an electrical sig
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What uses does infrared have?
Cooking- grills and toaster, Remote controls for TV, DVS players. Computers, mobile phones-communicate short distances. Security system detect heat from intruder. Used to carry information down optic fibres.
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How do inrared remote controls work?
They emit pulses of IR, the pulses act as an on off digital code. The device detects and decodes the pattern.
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What are the drawbacks with Infrared ratiation?
You need to be close to the device, they only travel in a straight line.
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What type of waves are P-waves
Longitudinal
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What type of waves are S-waves?
Transverse
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What are Longitudinal waves?
Vibrations go along the direction that the wave travels.
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What are tranverse waves?
The vibrations are at right angles to the direction that the wave travles.
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What properties do P-waves have?
They defracts as density changes, they travel through solids and liquids. They travel faster than S-Waves
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What properties do S-Waves have?
They only travel through solids and they are slower than P-Waves
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Other cards in this set

Card 2

Front

What causes substances to change their state?

Back

The kinetic energy makes the particles move around faster, in a solid the particles vibrate more rapidly.

Card 3

Front

What is an absolute scale?

Back

Preview of the front of card 3

Card 4

Front

In what direction does energy flow?

Back

Preview of the front of card 4

Card 5

Front

What is specific heat capacity?

Back

Preview of the front of card 5
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