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AQA GCSE - Unit 3 (P3,B3,C3) New specification papers. Watch

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    (Original post by tohaaaa)
    About the ventilation, is a positive pressure ventilator one that pumps air in, waits for air to go back out, then pumps in again?

    AND is a negative pressure ventilator the "Iron Lung"??
    Positive pressure ventilators are usually hand held pumps, however they can be automated ones used in operation theatres when patients are in a critical state and their breathing needs to be regulated. The positive pressure device forces air into the lungs through the trachea and creates positive pressure inside the lungs (higher that outside) This higher pressure forces the air out until it is equal to outside (note: the inside of the lung never ensures negative pressure with this method as it never pulls more air out causing the inside of the lung to have a lower pressure than outside). More air is then forced in

    Yes, the negative breathing aid is the Iron lung
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    (Original post by Hazwaz7)
    Can somebody help me think of more points for the biogas generator evaluation below? I've only got one point for disadvantages of continous generators...

    Evaluation continuous and batch biogas generators:

    Advantages of continuous over batch
    - more convenient (you don't have to keep emptying it, cleaning it, and refilling it)
    - steadier rate of biogas production (it is continuously being produced, therefore it is more time-efficient)
    - safer (less risk of accidents as it isn't emptied/cleaned/filled regularly)
    - less labour costs (nobody needs to keep emptying/cleaning/filling it)

    Disadvantages of continuous over batch
    - generator is more expensive
    In the specification, it asks specifically for an evaluation of the designs and production of gas. Not continual production or batches.

    E.g.
    disadvantages
    - Co2 is released in the process
    -The left over slurry is often toxic and hazardous to humans
    advantage
    - Good use of waste material
    - Free (excluding biogas generator)
    - More environmentally friendly
    - Can be used in remote locations (eg. india)

    E.g.
    disadvantages of buried (beneath ground) generators
    - Cooler beneath ground - won't get as hot which lessens the risk of enzymes denaturing
    - Ground provides insulation to keep it warm in cold conditions

    etc....
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    (Original post by grammar12)
    In the specification, it asks specifically for an evaluation of the designs and production of gas. Not continual production or batches.

    E.g.
    disadvantages
    - Co2 is released in the process
    -The left over slurry is often toxic and hazardous to humans
    advantage
    - Good use of waste material
    - Free (excluding biogas generator)
    - More environmentally friendly
    - Can be used in remote locations (eg. india)

    E.g.
    disadvantages of buried (beneath ground) generators
    - Cooler beneath ground - won't get as hot which lessens the risk of enzymes denaturing
    - Ground provides insulation to keep it warm in cold conditions

    etc....
    Oh, okay. I was under the impression that we had to know an evaluation of batch and continuous generators since in the spec it says we should be able to compare 'third-world' designs with 'commercial' designs... Plus in the CGP book it discusses batch and continuous generators.

    But thanks anyway

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    Would it be useful if i made a thread, exclusively for bio next week? this one is getting cluttered/overcrowded.
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    (Original post by Mrkingpenguin)
    Would it be useful if i made a thread, exclusively for bio next week? this one is getting cluttered/overcrowded.
    I think that would be a good idea. I think eventually it would be best if there be 3 separate threads for the 3 sciences as the exams approach us, in order to give us separate places for post-exam discussion/unofficial mark schemes etc.

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    (Original post by Hazwaz7)
    I think that would be a good idea. I think eventually it would be best if there be 3 separate threads for the 3 sciences as the exams approach us, in order to give us separate places for post-exam discussion/unofficial mark schemes etc.

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    Official biology discussion thread link below guys/girls!



    http://www.thestudentroom.co.uk/show...6#post42500356
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    (Original post by grammar12)
    Positive pressure ventilators are usually hand held pumps, however they can be automated ones used in operation theatres when patients are in a critical state and their breathing needs to be regulated. The positive pressure device forces air into the lungs through the trachea and creates positive pressure inside the lungs (higher that outside) This higher pressure forces the air out until it is equal to outside (note: the inside of the lung never ensures negative pressure with this method as it never pulls more air out causing the inside of the lung to have a lower pressure than outside). More air is then forced in

    Yes, the negative breathing aid is the Iron lung
    Ok thanks bro

    Also, about the Pros and Cons, the way I understand it is that the pros is that modern ventilators don't affect blood flow, and they keep the patient alive whilst they're waiting for an operation to "repair" the damaged lung. The disadvantage is that the patient is bed-bound and can't move around, and also the ventilator can cause burst alveoli if the lungs can't cope with the artificial air flow.

    Is this right?
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    Can someone please help explain some of B3 to me please, the particular topic being the structure of leaves and the stomata
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    (Original post by SportsFan)
    Can someone please help explain some of B3 to me please, the particular topic being the structure of leaves and the stomata
    Leaves have a flattened shape (to increase surface area for CO2 absorption), they also have air spaces within the leaf to further increase the surface area for CO2 absorption/gas exchange.

    - Transpiration also occurs from the leaf, transpiration is the loss of water from the plant by diffusion and evaporation.

    Water vapour and oxygen leave the plant via the stomata (see below)
    The Stomata allow gas exchange to occur in plants:

    - They are controlled by the guard cells

    When the conditions are right (high amounts of light), (correct me if I am wrong), water moves into the guard cells by osmosis, causing them to become turgid, this causes the stomata to open and gas exchange occurs.

    When the conditions are not right (night), water moves out of the guard cells (by osmosis) causing them to become flaccid, this closes the stomata and prevents water/gases from leaving the plant.

    Hope I helped (again, please shout if I'm wrong).
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    (Original post by Mrkingpenguin)
    Official biology discussion thread link below guys/girls!



    http://www.thestudentroom.co.uk/show...6#post42500356
    Are there any for the other two as of yet?
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    (Original post by Mrkingpenguin)
    Would it be useful if i made a thread, exclusively for bio next week? this one is getting cluttered/overcrowded.
    Here are the official ones:

    Biology

    http://www.thestudentroom.co.uk/show....php?t=2291132

    Chemistry

    http://www.thestudentroom.co.uk/show....php?t=2291120

    Physics

    http://www.thestudentroom.co.uk/show...9#post42502799
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    (Original post by CD223)
    Are there any for the other two as of yet?
    Biology

    http://www.thestudentroom.co.uk/show....php?t=2291132

    Chemistry

    http://www.thestudentroom.co.uk/show....php?t=2291120

    Physics

    http://www.thestudentroom.co.uk/show...9#post42502799

    These should help
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    too late bro, too late
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    (Original post by Mrkingpenguin)
    too late bro, too late
    considering they were made in March, no "bro". Not too late.
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    ahahah true that
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    (Original post by Mrkingpenguin)
    I did this for unit2 as well, trust me I know what im doing, ive added 6 marker poll + links to past papers + revision and warn people about post exam discission. I also add an unofficial ms after the exam which i need to be OP to do. You have done none of this- New to TSR are you? Dw, leave it to me.
    WOW, you're amazing! Me and my dinosaur ways and inexperience will just marvel at the amazement of your threads. Maybe improve your organisation as most people would have found that useful months before the exam, not one week away.
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    what are the grade boundaries for each

    also, is 39 an A* in the ISA
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    (Original post by grammar12)
    WOW, you're amazing! Me and my dinosaur ways and inexperience will just marvel at the amazement of your threads. Maybe improve your organisation as most people would have found that useful months before the exam, not one week away.
    Feel free to differentiate between a long term REVISION thread and a pre/post exam discussion thread. All I'm saying is that I have experience doing this and have talked to section mods regarding post exam discussion etc.
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    (Original post by Mrkingpenguin)
    Feel free to differentiate between a long term REVISION thread and a pre/post exam discussion thread. All I'm saying is that I have experience doing this and have talked to section mods regarding post exam discussion etc.
    That's wonderful. However, it is rude to create supposedly official exam discussion threads after a selection of others already have been created and then post on those threads the urls to your own unofficial exam discussions. I have no problem with other people creating discussions, just don't post them onto the original official threads because you weren't organised/bothered to create them earlier.
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    (Original post by grammar12)
    That's wonderful. However, it is rude to create supposedly official exam discussion threads after a selection of others already have been created and then post on those threads the urls to your own unofficial exam discussions. I have no problem with other people creating discussions, just don't post them onto the original official threads because you weren't organised/bothered to create them earlier.
    Just yourself, you mean. This thread is a general revision/all science thread. The OP is aware of my seperate bio thread as I told her. In fact she has kindly linked it in the second post.

    Please don't call me disorganised for creating threads now, the demand for them comes in the week before the exam, not a month (hence the last post in your thread is over a week old-and there's only been 4/5 posts in....a month). I put a lot of effort together with dalek1099 and two other users to publish topic predictions and unofficial markschemes and a complete list of links.

    Organised or bothered is perhaps the wrong choice of word. If you insist, then I will ask a mod to re direct your thread into mine, if not then to bad.

    Now, I have revision to do.
 
 
 
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