PHYA5 ~ 20th June 2013 ~ A2 Physics

Right first work out the total mass change if one uranium atom disintegrates,

so 390.406 + 1.675 - (149.357 + 239.056 + 2x1.675)

and you get a mass difference of 3.18 x 10^-27kg.

Now, for a uranium atom, there are 235g per mole. So if you want to find the mass change for 0.5kg, you do 500/235 x (6.0 x 10^23) and this will give you the number of uranium atoms in 0.5kg. You'll get an answer of 1.276 x 10^24 atoms.

Then you just multiply the mass difference if one uranium atom disintegrates by the number of uranium atoms you have, so (3.18 x 10^-27) x (1.276 x 10^24) and you'll get a final answer of 4.06 x 10^-4kg, or 406g.

Hope that helps!

But the mass difference you get 0.318^-27kg :confused:

Also what is argon dating ?
Thanks,
Smith

Reply 1161

Thr33

Original post by iwantopas19

hahaha omg..I wrote kekule :biggrin:

lol.. i hate chem...my worst nightmare.
I really felt like the paper was really really easy for anyone who understands chemistry (im not included)

Yeah, my hatred of Chemistry has grown sooooo much over the past couple of months. Admittedly, the paper did give out a lot of marks for really standard stuff - more of a memory test than anything. As I say though, a few tricky things that'll probably even out the scores.

Reply 1162

fwook

Anyone else got M2 on Friday but been focussing all their efforts on Physics, or is it just me? :biggrin:

Reply 1163

Caramelapps

2

Can anyone help me with Question 3.b)I) Section A (nuclear bit) of the June 2012 paper. Markscheme isn't helping me :-/ and cant get the right answer.

Reply 1164

Allahu Akbar

Original post by Thr33

Yeah, my hatred of Chemistry has grown sooooo much over the past couple of months. Admittedly, the paper did give out a lot of marks for really standard stuff - more of a memory test than anything. As I say though, a few tricky things that'll probably even out the scores.

Very sneaky :sneakydevil:

I thought we had to leave it a day for edexcel chemistry

Reply 1165

OmegaKaos

Original post by Caramelapps

Can anyone help me with Question 3.b)I) Section A (nuclear bit) of the June 2012 paper. Markscheme isn't helping me :-/ and cant get the right answer.

Its just knowing that gamma is emitted in all directions.
they tell you the area is 1.5*10^-3
But it spreads out inn relation to 4Pi*r^2(r=0,1.8)

so 1.5*10^-3/4Pi*(0.18)^2 = 3.68*10^-3
thats approx 4*10^-3

Reply 1166

Thr33

Original post by Allahu Akbar

Very sneaky :sneakydevil:

I thought we had to leave it a day for edexcel chemistry

Woops...I avoid the Chem forums like the plague and it's my only edexcel exam :evilbanana:

Reply 1167

sports_crazy

Astrophysics. Is there a difference between black body temperature in Wiens law and the temperature in Stefans law. I mean are this both surface temperature.

Reply 1168

laser174572

1

Original post by smith50

It was a 2 marker :tongue:

.Anyways I'm glad you get it now :smile:

Could you help me out on this question please

Thanks,
Smith

Out of interest, what paper/book is that question from?

Posted from TSR Mobile

Reply 1169

michael13

Original post by HEH95

done all 3 of the recent papers (june 10,11,12)

Was going to start looking at old spec papers for a bit this afternoon...can anyone confirm if this is worth doing?
ie. has the specification changed that much between june 09/june 10 ??

I found it helpful to solve some of the old papers as the specifications are almost identical.

Reply 1170

Matt III

This may have already been posted, but in the mark schemes for the mathsy questions they always seem to give one answer only and don't really talk about what happens if you give your answer to a different number of sig figs (assuming they didn't ask for it to be "an appropriate ammount" or an exact ammount.) Does anyone know what would happen if their answer was like "x=9.2" and you put "X=9.15"?

Reply 1171

smith50

6

Original post by laser174572

Out of interest, what paper/book is that question from?

Posted from TSR Mobile

I found it on the web :smile:

Smith

Reply 1172

UnknownOrigin

Original post by Science211

Hi, don't know if i'm overthinking this but could someone have a look at june 12 question 1)a) i seem to be getting 4.9 K rather than 17K

Thanks :biggrin:

Q = mc deltaT

We're told that it supplies 8500J per second, and the mass of water flowing through the heater per second is 0.12kg.

8500J = 0.12kgx4200 x deltaT

DeltaT = 8500/0.12x4200

DeltaT = 16.86

So round up for 17K

Reply 1173

UnknownOrigin

Also, what are people thinking for the six markers for the core/astro papers?

I'm personally hoping for thermal derivation of the pV=1/3NM(crms)^2, cause its mentioned on the spec.

For astro stellar evolution wouldn't be too bad, or comparing the advantages/disadvantages of refracting & reflecting telescopes. Not sure what else is a potential question really...

Reply 1174

Xiomara

18

Original post by Matt III

This may have already been posted, but in the mark schemes for the mathsy questions they always seem to give one answer only and don't really talk about what happens if you give your answer to a different number of sig figs (assuming they didn't ask for it to be "an appropriate ammount" or an exact ammount.) Does anyone know what would happen if their answer was like "x=9.2" and you put "X=9.15"?

I second this! Always wondered haha.

Reply 1175

laser174572

1

Original post by smith50

I found it on the web :smile:

Smith

Okay, thanks :smile:

Reply 1176

Cheezburger

1

Please help does anyone know where to find the mark schemes for the June 2010-12 papers? I can't seem to find them on the AQA website

Reply 1177

Hullo

8

Original post by Cheezburger

Please help does anyone know where to find the mark schemes for the June 2010-12 papers? I can't seem to find them on the AQA website

Sure? They're under the options section they'll have both options and core

Reply 1178

Hullo

8

Original post by Matt III

This may have already been posted, but in the mark schemes for the mathsy questions they always seem to give one answer only and don't really talk about what happens if you give your answer to a different number of sig figs (assuming they didn't ask for it to be "an appropriate ammount" or an exact ammount.) Does anyone know what would happen if their answer was like "x=9.2" and you put "X=9.15"?

It's not a sig fig question so you shouldn't worry too much, sometimes they'll even put the non rounded figure in brackets in the mark scheme like: 9.2 (9.15) but to be on the safe side just try to do the minimum sig figs in the question :smile:

Reply 1179

Science211