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# Fick's Laws of Diffusion: What ARE they for goodness sakes!!!!!???? Watch

1. Can someone please help me out. I need to know the laws of diffusion. I don't understand fick's laws. No website describes it properly, it just shows loads of equations. What are the laws?! ive been doing this for the past hour. google has not been my friend.

plus, im not sure if this belongs in chemistry or biology. or even physics. I just chose chemistry because it seems chemistry-ish.
2. Rate of diffusion is inversely proportional to the thickness of the gas exchange surface. The thicker the surface the slower the diffusion.

tl;dr the thinner the membrane the fast things can diffuse through it.

EDIT:
3. Fick's law states that

Rate of diffusion is proportional to (surface area of surface x concentration gradient)/(distance of diffusion pathway). It's very useful because it shows how changing certain factors can affect diffusion rates, and can be applied to physiological systems like the lungs.

The bigger the surface area or concentration gradient (difference in the concentrations between two regions), the faster the rate of diffusion, because they are on the 'numerator' effectively. The bigger the distance across which a substance must diffuse, the smaller the rate of diffusion (effectively the denominator).

Think about a fraction like 4/3. If we increase the numerator to 5/3, then the value has increased. But if we increase the denominator e.g. 5/4, the value has decreased. So we must reduce the diffusion distance to increase the rate of diffusion e.g. 5/3 --> 5/2

Hope that helped!

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Updated: December 26, 2010
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