AQA Physics PHYA5 - 28th June 2016 [Exam Discussion Thread]

Original post by Jay1421

Hey all - just uploaded the Thermal etc. section of the mark scheme to imgur, here's the link!

Unit 5 Thermodynamics, Radiation and Gases Unofficial Mark Scheme

As always, if there's anything in it that you believe to be wrong, be sure to let me know and I'll correct it! :smile:

Thanks!

Nice scheme, but I think for 4c, you'd gain only one mark for all of the points as the idea of the mean speed of the gas molecules would be necessary?

Reply 1262

Original post by kingaaran

Nice scheme, but I think for 4c, you'd gain only one mark for all of the points as the idea of the mean speed of the gas molecules would be necessary?

Was that question worth 3 marks?

Reply 1263

Original post by tanyapotter

Was that question worth 3 marks?

Nah don't think so. I'll have the official papers today, so will upload them later.

Posted from TSR Mobile

Reply 1264

Original post by kingaaran

Nah don't think so. I'll have the official papers today, so will upload them later.

Posted from TSR Mobile

Would you mind writing out what would be needed for 2 marks, and if it were worth 3 marks, then what would be needed for 3 marks? Thanks so much.

Reply 1265

Original post by tanyapotter

Would you mind writing out what would be needed for 2 marks, and if it were worth 3 marks, then what would be needed for 3 marks? Thanks so much.

I would say these are the three key ideas, although the second bullet point doesn't really deserve an extra credit in my opinion, making 2 marks apt:

increasing the temperature increases the mean kinetic energy of the gas molecules;

temperature is proportional to mean speed (squared) / mean kinetic energy of the gas molecules; *

hence the mean speed increases;

You need the idea of the 'mean' speed/kinetic energy for full credit. If it is not included anywhere, you'd drop 1 and ecf would be applied to give you 1/2.

(edited 7 years ago)

Reply 1266

SirRaza97

7

In the Nuclear and Thermal Physics part last question on specific heat. I used a rounded answer b) (ii). I used 1.6x10⁴ instead of 1.55 x 10⁴. So I got like 1700 for the heat capacity for ice instead of 2100. Hoow many marks would I lose?

Reply 1267

Original post by SirRaza97

In the Nuclear and Thermal Physics part last question on specific heat. I used a rounded answer b) (ii). I used 1.6x10⁴ instead of 1.55 x 10⁴. So I got like 1700 for the heat capacity for ice instead of 2100. Hoow many marks would I lose?

I don't remember the numbers, but I don't see how using an answer that is correct to 2 significant figures, instead of 3 significant figures, has given you only an accuracy of 1 significant figure.*

Reply 1268

SirRaza97

7

Original post by kingaaran

I don't remember the numbers, but I don't see how using an answer that is correct to 2 significant figures, instead of 3 significant figures, has given you only an accuracy of 1 significant figure.*

It makes a huge difference. Because there was a question before the heat capacity calc, where we needed to calculate how much heat energy was used to heat the ice (Can't remember exactly) and it gave you a value of 1.8x10⁴J was transferred from the water.

In the question to calc the heat capacity of ice we it told us that it went from -25 to 0 degrees. So how much was given to heat the ice was the energy transferred from water minus the heat capacity of ice.

1.8 x10⁴ - 1.55x10⁴ = 2500J

what I did was 1.8 x10⁴ - 1.6x10⁴ = 2000J

Then using Q = mc delta T where delta T = 25 and m = 0.047
when Q = 2000, c approx = 1700
when Q = 2500, c approx = 2100

You can see there is a missive difference if I use less sig figs. Which I unfortunately did.

Reply 1269

Original post by SirRaza97

It makes a huge difference. Because there was a question before the heat capacity calc, where we needed to calculate how much heat energy was used to heat the ice (Can't remember exactly) and it gave you a value of 1.8x10⁴J was transferred from the water.

In the question to calc the heat capacity of ice we it told us that it went from -25 to 0 degrees. So how much was given to heat the ice was the energy transferred from water minus the heat capacity of ice.

1.8 x10⁴ - 1.55x10⁴ = 2500J

what I did was 1.8 x10⁴ - 1.6x10⁴ = 2000J

Then using Q = mc delta T where delta T = 25 and m = 0.047
when Q = 2000, c approx = 1700
when Q = 2500, c approx = 2100

You can see there is a missive difference if I use less sig figs. Which I unfortunately did.

Oh, then of course, because it was a two stage calculation - I thought it was a one stage calculation.

At maximum, you would only lose one mark. The rest will be ecf. Although, I don't think you'll any, as the question was not testing significant figures at all, so it would be against the mark scheme to penalise you for it.

Reply 1270

SirRaza97

7

Original post by kingaaran

Oh, then of course, because it was a two stage calculation - I thought it was a one stage calculation.

At maximum, you would only lose one mark. The rest will be ecf. Although, I don't think you'll any, as the question was not testing significant figures at all, so it would be against the mark scheme to penalise you for it.

Thank you that puts my mind at ease! I really messed up in Unit 4 (probably got a low B) and want to make up for it in Unit 5. What do you think 60-62 marks will be? I took turning points as the optional

Reply 1271

Original post by SirRaza97

Thank you that puts my mind at ease! I really messed up in Unit 4 (probably got a low B) and want to make up for it in Unit 5. What do you think 60-62 marks will be? I took turning points as the optional

Probably an A*

Reply 1272

What are people thinking for the grade boundaries of this year's unit 5?

Reply 1273

mcride98

1

Original post by Jay1421

Hey all - just uploaded the Thermal etc. section of the mark scheme to imgur, here's the link!

Unit 5 Thermodynamics, Radiation and Gases Unofficial Mark Scheme

As always, if there's anything in it that you believe to be wrong, be sure to let me know and I'll correct it! :smile:

Thanks!

Will you be doing a Medical Physics unof mark scheme? It would help a lot :smile:

Reply 1274

Jay1421

2

Original post by kingaaran

Nice scheme, but I think for 4c, you'd gain only one mark for all of the points as the idea of the mean speed of the gas molecules would be necessary?

Yeah, you're probably right. Good catch.

Reply 1275

Jay1421

2

Original post by mcride98

Will you be doing a Medical Physics unof mark scheme? It would help a lot :smile:

Hi! Sadly I can't, as I don't have the Medical Physics paper, nor do I know the specification for it. Sorry! I'm sure somebody else will upload one at some point though :smile:

Reply 1276

Original post by Jay1421

Hi! Sadly I can't, as I don't have the Medical Physics paper, nor do I know the specification for it. Sorry! I'm sure somebody else will upload one at some point though :smile:

Hi! Do you have the Unit 5 nuclear physics paper? Thanks so much for your unofficial mark scheme. I was just wondering if you know exactly how many marks the answer about the speed of the molecules increasing with temperature, as you didn't specificy it in the mark scheme. I have a feeling it was worth 3 marks, but people keep saying it was worth only 2. Thanks!

Reply 1277

IsaacMed17

5

Original post by Jay1421

Yep! I'm midway through it at the moment, I'll be uploading it later tonight at some point - can't give a specific time though. Hope it helped so far!

Hi pal cheers for the section A. Anywhere near for the turning points?

Reply 1278

Jay1421

2

Original post by tanyapotter

Hi! Do you have the Unit 5 nuclear physics paper? Thanks so much for your unofficial mark scheme. I was just wondering if you know exactly how many marks the answer about the speed of the molecules increasing with temperature, as you didn't specificy it in the mark scheme. I have a feeling it was worth 3 marks, but people keep saying it was worth only 2. Thanks!

Hi - sorry, that was a mistake on my part - as people are saying, it was worth 2 marks.

Glad it helped!

Reply 1279