what is diffusion?

Answer 1

diffusion is when a compound is released in an area of high concentration and moves to an area of low concentration. like when you spray perfume in the back of a room diffusion is how you could smell it in the front after a short amount of time.

Answer 2

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration through a membrane. Diffusion is also a form of passive transport, meaning that it doesn't take any energy. Furthermore, osmosis is a form of diffusion; it is the diffusion of water molecules. Bear in mind though, water goes from an area of lower concentration to an area of higher concentration. Why? Well, because water is in need whenever there is a higher concentration of some solute.

Answer 3

The exchange of molecules between two or more gases is called diffusion.

Answer 4

its like a slow random mixing

when you put a drop of food coloring in water

what happens next is diffusion

Answer 5

Diffusion is the net action of matter (particles or molecules), heat, momentum, or light whose end is to minimize a concentration gradient. The process of diffusion, therefore, minimizes thermodynamic Gibbs free energy (though, it is not a chemical reaction), and is thus a spontaneous process (more familiarly known as a "passive" form of transport, rather than "active"). An example of diffusion is seen when one cooks spaghetti, where water diffuses into the sponge-like structure of the dry and stiff pasta. (Note that the heat provided by cooking does not cause but expedites this process).

The different forms of diffusion can be modeled quantitatively using the diffusion equation, which goes by different names depending on the physical situation. For instance - steady-state bi-molecular diffusion is governed by Fick's law, steady-state thermal diffusion is governed by Fourier's law. The diffusion of electrons in an electrical field leads essentially to Ohm's law that is further explained by Einstein relation. The generic diffusion equation is time dependent, and as such applies to non-steady-state situations as well.

In all cases of diffusion, the net flux of the transported quantity (atoms, energy, or electrons) is equal to a physical property (diffusivity, thermal conductivity, electrical conductivity) multiplied by a gradient (a concentration, thermal, electric field gradient). Noticeable transport occurs only if there is a gradient - for example in thermal diffusion, if the temperature is constant, heat will move as quickly in one direction as in the other, producing no net heat transport or change in temperature.

The second law of thermodynamics states that in a spontaneous process, the entropy of the universe increases. Change in entropy of the universe is equal to the sum of the change in entropy of a system and the change in entropy of the surroundings. A system refers to the part of the universe being studied; the surroundings is everything else in the universe. Spontaneous change results in dispersal of energy. Spontaneous processes are not reversible and only occur in one direction. No work is required for diffusion in a closed system. Reversibility is associated with equilibrium. Work can be done on the system to change equilibrium. Energy from the surroundings decrease by the amount of work expended from surroundings. Ultimately, there will be a greater increase in entropy in the surroundings than the decrease of entropy in the system working accordingly with the second law of thermodynamics.[1]

Diffusion can be measured, by the means of concentration gradient. A concentration gradient is the difference between the high concentration and the low concentration. It also determines how fast diffusion occurs.

Contents [hide]
1 Types of diffusion
2 Diffusion displacement
3 Isotope separation
3.1 Diffusion across biological membranes
4 References
5 See also
6 External links



[edit] Types of diffusion
Diffusion includes not only diffusion of particles, but all transport phenomena occurring within thermodynamic systems under the influence of thermal fluctuations (i.e. under the influence of disorder; this excludes transport through a hydrodynamic flow, which is a macroscopic, ordered phenomenon).

Diffusion is the process through which velocity thermodynamic system at local thermodynamic equilibrium returns to global thermodynamic equilibriums, through the homogenization of the values of its intensive parameters.




Atomic diffusion
Brownian motion, for example of a single particle in a solvent
Collective diffusion, the diffusion of a large number of (possibly interacting) particles
Effusion of a gas through small holes.
Electron diffusion, resulting in electric current
Heat flow (thermal diffusion)
Knudsen diffusion
Momentum diffusion, ex. the diffusion of the hydrodynamic velocity field
Osmosis
Photon diffusion
Reverse diffusion




[edit] Diffusion displacement
The diffusion displacement can be described by the following formula


where k is the dimensions of the system and can be one, two or three. D is the diffusion coefficient of the particles and t is time. For the three-dimensional systems the above equation will be:



[edit] Isotope separation
Gaseous diffusion
Liquid thermal diffusion

[edit] Diffusion across biological membranes
Facilitated diffusion
Ion diffusion through ion channels
Simple diffusion, not requiring a special protein channel
Diffusion in the respiratory system - in the alveoli of mammalian lungs, due to differences in partial pressures across the alveolar-capillary membrane, oxygen diffuses into the blood and carbon dioxide diffuses out