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AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread] Watch

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    (Original post by Lau14)
    They can definitely ask us about the first bit because that's just the basics of black body radiation (Wien's law), and I'd say the second bit isn't a huge jump (our teacher talked about it a fair bit) so it could come up I expect.
    Yeah, you just have the colours in the table for OBAFGKM - basically anything except green can turn up!
    Thank you!


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    (Original post by Normal.Person)
    GUYS!
    Just an fyi for everyone doing this exam, got some info that I thought might help everyone:
    No need to thank me.
    Spoiler:
    Show

    Oh, I'm just an AS student :P, but ya 18th of June is my birthday!


    That is not a way to make friends on this site


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    (Original post by Normal.Person)
    GUYS!
    Just an fyi for everyone doing this exam, got some info that I thought might help everyone:
    No need to thank me.
    Spoiler:
    Show

    Oh, I'm just an AS student :P, but ya 18th of June is my birthday!


    Lol, that's physics unit 5 nth birthday


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    (Original post by CD223)
    That is not a way to make friends on this site


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    LOOL, banter is good. Especially during exam time :P
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    (Original post by Normal.Person)
    LOOL, banter is good. Especially during exam time :P
    Times of high stress call for times of high level banter.


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    The moment where thermal physics makes you break down in tears!!


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    (Original post by runningoutoftime)
    The moment where thermal physics makes you break down in tears!!


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    I believe the moment hasn't come yet ;(


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    (Original post by runningoutoftime)
    The moment where thermal physics makes you break down in tears!!


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    I think it will be the six marker this year :/


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    (Original post by CD223)
    I think it will be the six marker this year :/


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    What do you think it could be one? Kinetic theory?


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    (Original post by runningoutoftime)
    What do you think it could be one? Kinetic theory?


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    Has ideal gas come up as a 6 marker before? I just really hate the kinetic theory
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    (Original post by runningoutoftime)
    What do you think it could be one? Kinetic theory?


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    (Original post by AR_95)
    Has ideal gas come up as a 6 marker before? I just really hate the kinetic theory
    Proof of the equation or a SHC/SLH experiment


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    (Original post by CD223)
    Proof of the equation or a SHC/SLH experiment


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    Proof of which equation?
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    (Original post by CD223)
    Proof of the equation or a SHC/SLH experiment


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    i thought we didnt have to dervive the equation?
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    Things I hope come up :

    Standard "calculate ze age of ze isotope"

    How a nuclear reactor works questions

    Standard Q=MCT question

    Also out of the 4 topics in PH5, which one do you find the easiest when solving the numerical questions? For me it's all the gases parts
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    hello, stuck on this question, any ideas?

    Question 13 on here

    http://www.wolgarston.staffs.sch.uk/...-201415-20.pdf


    Some liquids in open bottles deteriorate on exposure to air. The diagram below shows one device used to reduce this deterioration. It consists of a rubber valve that is inserted into the neck of the bottle together with a pump that is used to remove some of the air in the bottle through this rubber valve. On an up-stroke of the pump, air enters the pump chamber from the bottle. On the down-stroke, the rubber valve closes and the air in the chamber is expelled to the atmosphere through another valve (not shown) in the handle.

    a.) There is 3.5 × 10–4 m3 of air space in the bottle and the volume of the pump chamberchanges from zero at the beginning of the up-stroke to 6.5 × 10–5 m3 at the end of the up-stroke. The initial pressure of the air in the bottle is that of the atmosphere with a value of99 kPa.

    Assuming the process is at constant temperature, calculate the pressure in the bottle afterone up-stroke of the pump.

    b.) Calculate the number of molecules of air originally in the air space in the bottle at atemperature of 18 °C.

    c.) Explain how the kinetic theory of an ideal gas predicts the existence of a gas pressureinside the bottle. Go on to explain why this pressure decreases when some of the air isremoved from the bottle.



    answers in spoiler
    Spoiler:
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    Answers

    (a) use of pV = constant or p1V 1 = p2V2 (1) p = 99 × 3.50/4.15 (1) = 83.5 kPa (1) 3 (where did 4.15 come from???)

    (b) no. of moles = 99 [× 10] × 3.5 × 10–4/8.31 × 291 (1) = 1.4(3) × 10–2 moles (1) no. of molecules (= 1.4(3) × 10–2 × 6.02 × 10–23) = 8.6(1) × 10–21 (1) 3 (i used pV=Nkt and got 8.62x10^21 +21 rather than -21???)

    (c) molecules/particles have momentum (1) momentum change at wall (1) momentum change at wall/collision at wall leads to force (1) [allow impulse arguments] less air so fewer molecules (1) so change in momentum per second/rate of change is less [or per unit per time] (1) pressure is proportional to number of molecules (per unit volume) (1) max 5

    thank you in advance
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    (Original post by imyimy)
    ([i]where did 4.15 come from???
    Before there was only volumes inside bottle after theres is volme of both bottle and the pump(or valve etc)
    So you add both volumes.

    3.5 x 0^-4 +6.5x10^-5 = 4.15 x 10^-4

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    (Original post by imyimy)
    used pV=Nkt and got 8.62x10^21 +21 rather than -21???)[/i]

    Use pV=nRT

    Small n is number of moles
    Big N is number particles

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    (Original post by a.a.k)
    Use pV=nRT

    Small n is number of moles
    Big N is number particles

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    thanks

    but the question asks for molecules not moles
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    (Original post by imyimy)
    thanks

    but the question asks for molecules not moles
    Oh sorry my bad

    Yeah u find the number if moles then divide by avagadro constant to get number of particles or in this case number of molecules

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    In one moles there are 6.02x10^-23 particles

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