# OCR P7 Unofficial Mark Scheme - Friday 23rd June 2017

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Thread starter 5 years ago
#1
Here's an unofficial mark scheme for today's exam: it's incomplete, missing about 20 or so marks.

P7 Unofficial Mark Scheme

1. Which telescope was best? (6 marks)
Space
Advantages - less absorption and refraction due to atmosphere, can get clearer images, no water ect
Disadvantages - 7x more expensive than the other one, hard to maintain, money could be used better elsewhere

Mountain
Advantages - cheaper, higher up so less affected by light pollution, less absorption by water because there's dry air
Disadvantages - still some absorption ect Make a conclusion - pick one and say which is better.

2. Explain why we get different moon phases (3 marks)
Each moon type is due to different amounts of light being reflected by the sun (1) It's constant because the moon is always orbiting the earth (1)

3. Explain why moon phases take longer than moons orbit (2 marks)
Not sure what this wanted - any help?

4. What happens to temperature and pressure and volume (2 marks)
Increases, increases, stay the same (2)

5. Explain this in terms of particles (3 marks) More temperature = more kinetic energy (1) More energy = more collisions (1) More collisions = more pressure on walls (1)

6. Movement of the stars (4 marks)
Pole star stays in same position (1)
Each other star moved 1/4 of a circle (1 for each)

7. Explain how astronomers use reflection, diffraction and refraction (6 marks)

8. Calculate pressure (3 marks)
1200 (3)

9. Explain measurements to stars and limitations (6 marks)

Parallax - apparent movement, half the angle travelled in a 6 month period, angles can get hard to measure

Luminosity depends on temperature and size - compare two stars with same luminosity but different observed brightness. Greater observed brightness = closer. Can be hard to find two stars with same luminosity.

10. Calculate mass in kg (4 marks)
1.1x10^8

11. Work out energy produced (3 marks) 6.336*10^44 (2)
J (1)

12. Circle what measurements he needs (2 marks)
Angle (1)
Height (1)

13. Tick boxes about spectrums (2 marks)
Top box (1)
Bottom box (1)

14. Explain why high mass stars spend less time in main sequence (3 marks)
Greater pressure and temperature (1) so they can fuse elements quicker (1) so hydrogen fusion stops sooner to fuse larger elements such as helium so it moves out of main sequence (1)

15. Name the process in a star (1 mark)
Nuclear fusion

16. Correlation and inversely proportional (4 marks)
Yes there is a correlation as when mass decreases, time increases (1)
Not directly proportional (give an example) and say that they both don't produce the same constant (2)
Therefore it's not inversely proportional (1)

17. Fill in gaps about retrograde motion (3 marks)
Planets (1)
Backwards (1)
Stars (1)

18. Explain why they peer review (1 mark)
To increase confidence in their collected results

19. Explain why the data is theoretical (2 marks)
UNSURE - might be because one of the stars was 20,000 billion years old and universe is only 14,000 billion so we haven't seen one happen. Or, it's difficult to find mases of stars?
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5 years ago
#2
four marker on that correlation about inversely proportional
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Thread starter 5 years ago
#3
(Original post by Sum Ting)
four marker on that correlation about inversely proportional
Yes!

Thankyou...
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Thread starter 5 years ago
#4
The realisation that you did directly proportional instead of flaming inversely proportional for the 4 marker...really not into double figures yet.
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Thread starter 5 years ago
#5
Can anyone remember any more questions?

TheMightyBadger can you remember any?
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Thread starter 5 years ago
#6
(Original post by Harryjamieson23)
Just a few thoughts...
2-Could you mention lunar eclipses?
3-Maybe only 2 marks?
7-Would Diagrams be acceptable?
11- I thought it was 7.04x10^27
14-I think that High Temp+High Pressure-->Faster Rate of Fusion-->Used up faster
17-I put Faster instead of backwards-Is that right?

There was a 1 marker on peer review and a 2 marker on why the data was computer-generated
Added those two questions in - will have a look at your suggestions in a sec.
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Thread starter 5 years ago
#7
(Original post by Harryjamieson23)
Just a few thoughts...
2-Could you mention lunar eclipses?
3-Maybe only 2 marks?
7-Would Diagrams be acceptable?
11- I thought it was 7.04x10^27
14-I think that High Temp+High Pressure-->Faster Rate of Fusion-->Used up faster
17-I put Faster instead of backwards-Is that right?

There was a 1 marker on peer review and a 2 marker on why the data was computer-generated
2 - probably, not really sure what it wanted.
3 - one of the ones about moons was three marksx not sure which
7 - yes diagrams will be accepted
11 - don't think that's right
14 - yes because the fusion occurs quicker so larger elements start to be formed quicker which moves it out of main sequence
17 - I'm sure it said "and they appear to move............" so I think it's backwards.
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5 years ago
#8
I'm sure it was deceased decreased stays the same. When u decrease temperature the pressure decreases, that's what it was asking for question 4
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5 years ago
#9
how did u get 1200 for pressure? i got something like 1273
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5 years ago
#10
(Original post by kiranjit)
how did u get 1200 for pressure? i got something like 1273
for the pressure one u were meant to i work out the constant and then the pressure and u had to convert °C into K
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Thread starter 5 years ago
#11
(Original post by kiranjit)
for the pressure one u were meant to i work out the constant and then the pressure and u had to convert °C into K
Yes - felt it was a bit mean for only three marks as you had to convert between Celsius and kelvin twice, work out a constant and apply a formula
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5 years ago
#12
(Original post by danielwinstanley)
Yes - felt it was a bit mean for only three marks as you had to convert between Celsius and kelvin twice, work out a constant and apply a formula
i did all of that but i didn't get 1200
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Thread starter 5 years ago
#13
(Original post by kiranjit)
i did all of that but i didn't get 1200
Did you get constant as 4?
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5 years ago
#14
(Original post by danielwinstanley)
Did you get constant as 4?
yeah and then i multiplied it by 50+273=323 because u need to add 273 to convert celsius to kelvin which gave me 1292 pa
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5 years ago
#15
(Original post by kiranjit)
yeah and then i multiplied it by 50+273=323 because u need to add 273 to convert celsius to kelvin which gave me 1292 pa
the pressure was 1200 to work out the constant it wasn't for the overall preside because they gave us the volume and temperature
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5 years ago
#16
(Original post by kiranjit)
the pressure was 1200 to work out the constant it wasn't for the overall preside because they gave us the volume and temperature
pressure**
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Thread starter 5 years ago
#17
(Original post by kiranjit)
yeah and then i multiplied it by 50+273=323 because u need to add 273 to convert celsius to kelvin which gave me 1292 pa
Was there a different starting temperature?
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5 years ago
#18
(Original post by danielwinstanley)
Was there a different starting temperature?
the starting the starting temperature was 300K and the volume was fixed at a certain ml so u workout the pressure which was u 1200 divide it by 300 to give u the constant 4
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5 years ago
#19
for the six marker on diffraction, refraction and reflection could you discuss diffraction gratings?
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5 years ago
#20
How did everyone find the p7 exam?
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