Diffusion is the net movement of molecules or atoms from a region of a high concentration (or a high chemical potential) to a low concentration(or a low chemical potential). This is also known as the movement of a substance down a concentration gradient. A gradient is the change in the value of a quantity with the change in another variable. For example, a change in the concentration over a distance is called a concentration gradient. A change in the pressure over a distance is called a pressure gradient. A change in the temperature over a distance is called a temperature gradient. In this picture, some of the particles are dissolved in a glass of water. At first. the particles are all near on one corner of the glass. If the particles all randomly move around in the water, they will eventually become randomly scattered and distributed evenly among the glass of water.
Diffusion plays an important role in the life of a cell. Diffusion is the result of the random thermal movements of the molecules, and it involves molecules spreading from regions of the high concentration (or where there are lots of molecules) into the regions of the low concentration levels (or where there are fewer molecules). This is known as the concentration Gradient. The diffusion rate is affected by the concentration gradient, the size of molecules involved, the temperature, the distance a molecule has to travel, the solubility of the molecule, and the surface area of the membrane. Molecules dissolved in a solution are in constant random motion due to their kinetic energy. One result of this motion is that dissolved molecules become evenly distributed throughout the solution. Unlike some of the other chemical reactions, no catalyst is needed to start the process of diffusion, because of the internal energy of the individual molecules. Diffusion can be accelerated by the proteins in the membrane. Molecules are in a constant motion because of their internal energy. Internal Energy is the random motion of atoms and molecules on a microscopic scale. However, since the average internal energy of every type of molecule is different, diffusion happens at different rates of speed depending on the make up of the substance. Diffusion rate is how fast one substance spontaneously mixes with another. Diffusion can usually happen in the form of a gas. Diffusion can also happen in the form of a liquid. It is passible to see diffusion happening when 2 of the liquids are mixed in a transparent container. Diffusion describes the constant movement of particles in all liquids and gases. These particles move in all directions, bumping into each other. Diffusion can only work with gases and liquids. Diffusion is the fastest in gases because the particles can move quickly throughout the gases. Diffusion in liquids is slower compared to gases because particles move slowly throughout the liquids. Diffusion does not occur in solids because particles in solids only vibrate on the spot, rather than moving from place to place in the solution.