Difference Between Diffusion and Osmosis

Main Difference – Diffusion vs Osmosis

These are two processes that are involved in the transfer of material from one position to another. However, by definition they are very different from each other. The main difference between diffusion and osmosis can be identified by their definitions themselves. Diffusion is the net transfer of molecules/ material from a high concentration zone to a low concentration zone. Osmosis is the transfer of a solution through a semi-permeable membrane from a region of low concentration to a region of high concentration.

What is Diffusion

Diffusion can take place across any medium. It is most common among gasses and liquids. This is the net transfer of solute molecules from an area of high concentration to an area of low concentration. It is said to be concentrated when there are a lot of solute molecules occupying a small area of space. And when the opposite takes place, it is said to be low in concentration. There is a natural tendency for materials to move from a high concentration zone to a low one until they become similar in concentration. At this point, it can be thought that the net transfer of solutes is ‘0.’

This kind of movement is due to the empty space present in the medium, allowing the solutes to move through space. Therefore, diffusion can be taken as an example to prove that matter is not continuous. Few examples for this process include; the smell of a perfume hitting our nose (due to the movement of scent molecules through the medium of air), the spread of a dye through a glass of water (the dye molecules move through the empty spaces present in the water medium to fill equally fill the glass).

What is Osmosis

This process involves the movement of a solution through a semi-permeable membrane from a low concentration zone to a high concentration zone. A semi-permeable membrane is a membrane that is only able to let certain types of material pass through it; usually it allows the passage of liquid molecules and prevent the entry of solids. In contrast, a fully permeable membrane would have no control of the material that pass through it.

In the case of osmosis, two solutions with different concentrations are kept separated by a semi-permeable membrane. What happens in this case, is that the region with more solution flows through to the region with less solution in order to level the concentrations. However, since the term ‘concentration’ is defined based on the solutes instead of the solution, the transfer of solution is said to take place from an area of high concentration to an area low concentration. An ideal example for a semi-permeable membrane that is found naturally is the cell membrane. And a good example of osmosis would be the entrance of water into a cell. When there is no net movement of solution across the membrane, the system is said to be at osmotic pressure.