4th entry(chem) : Diffusion

What is Diffusion?

The process Diffusion is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion.

Basically, it is the movement of molecules from an area of high concentration to a lower area.

When the molecules are even throughout a space - it is called EQUILIBRIUM.

Concentration gradient is a difference between concentrations in a space.

Experiment:

Consider two containers of gas A and B separated by a partition. The molecules of both gases are in constant motion and make numerous collisions with the partition. If the partition is removed as in the lower illustration, the gases will mix because of the random velocities of their molecules. In time a uniform mixture of A and B molecules will be produced in the container.
The tendency toward diffusion is very strong even at room temperature because of the high molecular velocities associated with the thermal energy of the particles.


References:
http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/diffus.html
http://en.wikipedia.org/wiki/Molecular_diffusion
http://www.biologycorner.com/bio1/diffusion.html