AQA P1.1 Transfer of energy by heating

?
  • Created by: Rchilds
  • Created on: 15-05-17 21:24
What is infrared radiation?
It is a section of the electromagnetic spectrum that transfers heat energy. It is a WAVE (doesn't need particles)
1 of 46
Which objects give out infrared radiation?
All objects
2 of 46
What is the relationship between the temperature of an object and the amount of infrared it emits?
The larger the temperature difference between the object and it's surroundings, the more infrared is emitted. i.e. hotter objects give off more infrared.
3 of 46
What types of surfaces are the best EMITTERS of infrared?
Dark, matt surfaces
4 of 46
What types of surfaces are the best ABSORBERS of infrared?
Dark, matt surfaces
5 of 46
Which surfaces are the worst emitters and absorbers of infrared and why?
Light, shiny surfaces because they REFLECT the infrared
6 of 46
How do cooling fins work?
They increase the surface area and are black/matt in colour, both of these increase the rate of heat loss
7 of 46
Tips for drawing the particle diagram of solids?
Make sure all the particles are circular and the same size, put them in neat rows with each particle touching the surrounding particles
8 of 46
Tips for drawing the particle diagram of liquids?
Draw circular particles that are all the same size. No neat rows (must be random) but most of the particles should be touching. There can be some small gaps, but no gaps big enough to fit another particle.
9 of 46
Tips for drawing the particle diagram of gas?
Only draw 3, equally sized, particles, with big gaps and draw them randomly
10 of 46
How do solid particles move?
Vibrate around a fixed position
11 of 46
Explain the properties of solids
Dense, fixed shape, not able to compress - because particles have STRONG INTERMOLECULAR BONDS and a tightly packed, the are not able to flow
12 of 46
How do liquid particles move?
Flow randomly
13 of 46
Explain the properties of liquids
Dense, can flow, not able to compress - particles have QUITE STRONG INTERMOLECULAR BONDS but can move around (flow), however they are tightly packed so can't be compressed
14 of 46
How do gas particles move
Randomly
15 of 46
Explain the properties of gases
Low density, can flow, easy to compress - particles are very spread out with WEAK INTERMOLECULAR BONDS so can move around easily (randomly), large gaps means they can be compressed.
16 of 46
When you heat up a substance, what happens to it?
It's kinetic energy increases (temperature is proportional to kinetic energy)
17 of 46
What types of substances does conduction happen in and what are the best types of conductors?
It happens in solids, metals are the best conductors
18 of 46
What is conduction?
When you heat up a solid, it's particles gain kinetic energy and vibrate more. They collide with the particles next to them and transfer this energy through the solid
19 of 46
Why are metals the best conductors?
Normal conduction happens (see previous card) but metals also have free (delocalised) electrons that gain KINETIC energy then move through the metal (diffuse through the metal) and transfer energy by colliding with other electrons or with ions
20 of 46
Why are some materials good insulators?
They might have trapped gas in them, gas particles are too far apart to conduct well. (Sometimes the particles in insulators aren't able to vibrate very much, e.g. polymers are too tangled)
21 of 46
Give some examples of good insulators that work because they have trapped gas in them
cotton wool, fluffy blankets, fluffy coats, wall cavity and loft insulation, bubble wrap etc
22 of 46
What types of substances does convection happen in?
Liquids and gases (particles need to be able to flow to carry energy)
23 of 46
What is a convection current?
When a liquid or gas is heated the particles gain KINETIC energy and move apart and so becomes LESS DENSE. Less dense fluids RISE UP. Cooler fluids are more dense so sink and replace the hot fluid that has risen.
24 of 46
What is the convection limerick?
When a liquid or gas gets some heat; it expands, is less dense, so retreats; rises up but then cools; contracts and then falls; and then the process repeats
25 of 46
How can you stop convection and conduction?
Use a vacuum (an area of space with no particles) as they both need particles
26 of 46
What type of heat transfer is the only one that can travel through a vacuum?
infrared radiation (because it's a wave)
27 of 46
How do you reduce the amount of heat transfer by infrared radiation?
Use a shiny surface to reflect it.
28 of 46
What factors effect the rate of heat transfer?
Surface area (large = quicker), volume (small = quicker), the material that the object is made from and in contact with (thickness and type), the temperature DIFFERENCE between the object and it's surroundings
29 of 46
How does evaporation work?
In a liquid the particles have a RANGE OF ENERGIES. Some particles will have enough energy to break the INTERMOLECULAR BONDS nd escape the liquid, however they can only do this if they are at the SURFACE of the liquid
30 of 46
How do you increase the rate of evaporation?
Larger surface area (more particles on the surface so more can escape), heat the liquid (more particles will have enough energy), air flow over the liquid (saturated air cannot hold anymore escaped liquid so a breeze move it away),
31 of 46
How does evaporation have a cooling effect?
The most energetic particles leave the liquid. This means the particles left behind have a lower average (kinetic) energy (and kinetic energy is proportional to temperature so the temperature is also lower)
32 of 46
What is condensation?
When energy is removed from gas so it turns into a liquid e.g. on a cold surface
33 of 46
How do you reduce condensation?
Heat the surface
34 of 46
How do you prevent evaporation?
Use a lid. The evporated particles will condense on the lid and drip back down into the liquid
35 of 46
How are animals in warm climates adapted?
Large surface area to volume ratio e.g. large ears to increase the RATE of heat loss
36 of 46
How are animals in cold climates adapted?
Small ears, small surface area to volume ratio to reduce the RATE of heat loss
37 of 46
What is a U-value?
A measurement of how good a material is at being an insulator (to do with the rate of energy loss through the material), the lower the U-value, the better it is at insulating
38 of 46
What are solar PANELS?
Panels that absorb the suns heat energy and use it to heat water (so the home owner doesn't need their boiler as much). NOTE: this is different to a solar CELL
39 of 46
What does specific heat capacity mean?
The specific heat capacity of a substance is the amount of energy required to change the temperature of one kilogram of the substance by one degree Celsius.
40 of 46
Why can materials with a high specific heat capacity be useful?
They can store a lot of energy without a big temperature rise e.g. storage heaters, water coolers etc
41 of 46
Explain how a sea breeze works
Sand has a low specific heat capacity compared to water so heats up quickly form the sun's heat energy. The sand then heats the air above it, which becomes LESS DENSE so RISES. It is then replaced by the cool, more dense air over the sea (convection)
42 of 46
In experiments involving heat energy, what is the standard answer for why your experimental values might be too high or too low?
Heat energy is lost to the surroundings (that you haven't accounted for in calculations) so INSULATE the experiment
43 of 46
How does a vacuum flask work?
Plastic lid - poor conductor, prevents a convection current being set up and prevents heat loss from evaporation. If there is glass - glass is a poor conductor so reduces conduction. Vacuum - no particles = stops conduction and convection (continued)
44 of 46
Vacuum flask continued....
shiny surface - reflects infrared radiation back into liquid. Shiny surfaces are also poor emitters so reduces heat loss by radiation to the surroundings
45 of 46
When considering an argument for a design, what factors can you consider?
(1) economic (money), (2) social and political (people's jobs, health etc), (3) environmental (habitats, green house gases etc) (4) availability (can you put it anywhere? Is it easy to find?)
46 of 46

Other cards in this set

Card 2

Front

Which objects give out infrared radiation?

Back

All objects

Card 3

Front

What is the relationship between the temperature of an object and the amount of infrared it emits?

Back

Preview of the front of card 3

Card 4

Front

What types of surfaces are the best EMITTERS of infrared?

Back

Preview of the front of card 4

Card 5

Front

What types of surfaces are the best ABSORBERS of infrared?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Physics resources:

See all Physics resources »See all Energy resources »