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==Key Stage 3==
===Meaning===
[[Diffusion]] is when [[particlesparticle]] s spread from a region of high [[concentration]] to a region of low [[concentration]].
===About Diffusion===
: [[Diffusion]] can only happen in a [[fluid]] which means (a [[liquid]] or a [[gas]] ) because the [[particle]]s can move past each other.
: [[Diffusion]] cannot happen in a [[solid]] because the [[particle]]s are held in fixed positions.
: In [[diffusion]] the particles [[particle]]s always spread from a high [[concentration]] (where there is are lots of the substance[[particle]]s, to a low [[concentration]] (where there is are less of the substance.: [[Diffusion]] stops when all substances are spread out equally and there is no longer a [[Concentration Gradient|concentration gradientparticle]]s).
{| class="wikitable"
| style="height:20px; width:600px; text-align:center;" |This [[diagram]] shows a high [[concentration]] of blue [[particle]]s on the left separated from the red [[particle]]s by a barrier. When the barrier is removed the blue [[particle]]s [[Diffusion|diffuse]] to the area of lower [[concentration]] on the right. [[Diffusion]] continues until all [[particle]]s are equally spread.
|}
{| class="wikitable"
|-
|[[File:Diffusion.gif|center]]
|-
| style="height:20px; width:600px; text-align:center;" |This animation shows a high [[concentration]] of red [[particle]]s initially at the top. When [[diffusion]] begins the red [[particle]]s spread to the area of lower [[concentration]] at the bottom. [[Diffusion]] continues until all [[particle]]s are equally spread.
|}
==Key Stage 4==
===Meaning===
[[Diffusion]] is when [[particle]]s spread from a region of high [[concentration]] to a region of low [[concentration]] along a [[Concentration Gradient|concentration gradient]].
===About Diffusion===
: [[Diffusion]] can only happen in a [[fluid]] (a [[liquid]] or a [[gas]]) because the [[particle]]s can move past each other.
: [[Diffusion]] cannot happen in a [[solid]] because the [[particle]]s are held in fixed positions.
: In [[diffusion]] the [[particle]]s always follow the [[Concentration Gradient|concentration gradient]] spreading from a high [[concentration]] (where there is lots of the [[particle]]s), to a low [[concentration]] (where there are less of the [[particle]]s).
: [[Diffusion]] stops when all [[substance]]s are spread out equally and there is no longer a [[Concentration Gradient|concentration gradient]].
{| class="wikitable"
|-
|[[File:Diffusion.png|center|600px]]
|-
| style="height:20px; width:600px; text-align:center;" |This [[diagram]] shows a high [[concentration]] of blue [[particle]]s on the left separated from the red [[particle]]s by a barrier. When the barrier is removed the blue [[particle]]s [[Diffusion|diffuse]] to the area of lower [[concentration]] on the right. [[Diffusion]] continues until all [[particle]]s are equally spread.
|}
{| class="wikitable"
|-
|[[File:Diffusion.gif|center]]
|-
| style="height:20px; width:600px; text-align:center;" |This animation shows a high [[concentration]] of red [[particle]]s initially at the top. When [[diffusion]] begins the red [[particle]]s spread to the area of lower [[concentration]] at the bottom. [[Diffusion]] continues until all [[particle]]s are equally spread.
|}
===References===
====AQA====
:[https://www.amazon.co.uk/gp/product/1782945954/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945954&linkCode=as2&tag=nrjc-21&linkId=100574c08fbbb64318256eb79ed61a76 ''Diffusion pages 51-53, GCSE Biology, CGP, AQA '']
:[https://www.amazon.co.uk/gp/product/0198359373/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359373&linkCode=as2&tag=nrjc-21&linkId=952a73bbb09d222ecc4b50d200679849 ''Diffusion, pages 14-15, 61, 188-189, GCSE Biology; Third Edition, Oxford University Press, AQA '']
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09843 ''Diffusion, pages 17, 20, 21, GCSE Combined Science; The Revision Guide, CGP, AQA '']
:[https://www.amazon.co.uk/gp/product/1782945563/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945563&linkCode=as2&tag=nrjc-21&linkId=9a1d023a374038e6072f33c4f3cf808b ''Diffusion, pages 20, 21, 23-25, GCSE Biology; The Revision Guide, CGP, AQA '']
:[https://www.amazon.co.uk/gp/product/0008158754/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158754&linkCode=as2&tag=nrjc-21&linkId=27ad53b0283feeff7fc5ae04a9e205f221 ''Diffusion, pages 44-5, 55, 68-9, 86-7. 92, 94-5, 101, 106-7, 113, 117, 204, GCSE Biology; Student Book, Collins, AQA '']
:[https://www.amazon.co.uk/gp/product/1782946381/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946381&linkCode=as2&tag=nrjc-21&linkId=5ec5fc3f6429e30c1d9ab9bca2bccf93 ''Diffusion, pages 45-47, GCSE Combined Science Trilogy; Biology, CGP, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851338/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851338&linkCode=as2&tag=nrjc-21&linkId=425855d5890466e47189e1c21b67a1ea ''Diffusion, pages 5, 28, 29-33, GCSE Biology, Hodder, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion, pages 5, 29, GCSE Combined Science Trilogy 1, Hodder, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion; in other organisms, pages 31-2, GCSE Combined Science Trilogy 1, Hodder, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion; in the lungs, page 30, GCSE Combined Science Trilogy 1, Hodder, AQA '']
:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion; influencing factors, pages 32-3, GCSE Combined Science Trilogy 1, Hodder, AQA '']
====Edexcel====
:[https://www.amazon.co.uk/gp/product/1782948120/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948120&linkCode=as2&tag=nrjc-21&linkId=dedef775c6a43dbb0a609441525adac0 ''Diffusion, factors affecting rate, page 258, GCSE Biology, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1782945741/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945741&linkCode=as2&tag=nrjc-21&linkId=30da4f2178da182547b62a7329d13b57 ''Diffusion, page 18, GCSE Combined Science; The Revision Guide, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1782946748/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946748&linkCode=as2&tag=nrjc-21&linkId=a4f0348fc37d0ba1bb52d27f8679581f ''Diffusion, page 21, GCSE Biology; The Revision Guide, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1292120193/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120193&linkCode=as2&tag=nrjc-21&linkId=572df39392fb4200db8391d98ae6314e ''Diffusion, pages 20, 92-93, 112, GCSE Combined Science, Pearson Edexcel '']
:[https://www.amazon.co.uk/gp/product/1292120207/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120207&linkCode=as2&tag=nrjc-21&linkId=22455ff53961978667722edaa64c0be5 ''Diffusion, pages 24, 130-131, 162, GCSE Biology, Pearson, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1782948120/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948120&linkCode=as2&tag=nrjc-21&linkId=dedef775c6a43dbb0a609441525adac0 ''Diffusion, pages 48, 49, GCSE Biology, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1782946748/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946748&linkCode=as2&tag=nrjc-21&linkId=a4f0348fc37d0ba1bb52d27f8679581f ''Diffusion; factors affecting rate, page 88, GCSE Biology; The Revision Guide, CGP, Edexcel '']
:[https://www.amazon.co.uk/gp/product/1292120207/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120207&linkCode=as2&tag=nrjc-21&linkId=22455ff53961978667722edaa64c0be5 ''Diffusion; factors affecting, pages 164-165, GCSE Biology, Pearson, Edexcel '']
====OCR====
:[https://www.amazon.co.uk/gp/product/0198359829/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359829&linkCode=as2&tag=nrjc-21&linkId=90e8d7b4f039d53035238fa0320fe00b ''Diffusion, page 123, Gateway GCSE Chemistry, Oxford, OCR '']
:[https://www.amazon.co.uk/gp/product/1782945695/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945695&linkCode=as2&tag=nrjc-21&linkId=ceafcc80bcad6b6754ee97a0c7ceea53 ''Diffusion, page 25, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR '']
:[https://www.amazon.co.uk/gp/product/1782945660/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945660&linkCode=as2&tag=nrjc-21&linkId=83aa4500ad7759e7f401a1c5ba5df758 ''Diffusion, pages 30, 33, Gateway GCSE Biology; The Revision Guide, CGP, OCR '']
:[https://www.amazon.co.uk/gp/product/0198359810/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359810&linkCode=as2&tag=nrjc-21&linkId=d768d99f1a06f7c12fab40e5aef85a55 ''Diffusion, pages 58-59, 72-73, Gateway GCSE Biology, Oxford, OCR '']