What is Diffusion?


Diffusion is the random movement of molecules in a gas or liquid. It can be facilitated or non-facilitated, and chemical factors can affect it. For example, if you add vegetable oil to water, it will not diffuse. However, they will diffuse if you add dissolved solids to the same liquid.

Facilitated diffusion

Facilitated diffusion is a process in which molecules move from one place to another. It occurs in cells and regulates the number of molecules and ions in a cell. The mechanism is based on the fact that a carrier protein has a pore on its surface, and the molecule to be transported can enter the pore and become bound to the carrier protein. Then, the carrier protein changes conformation to open the pore and transport the molecule to the other side of the membrane.

Facilitated diffusion is a natural process. It occurs in living cells and is a key step in cell metabolism. It allows sugars and amino acids to move across the plasma membrane. This is done by a group of carrier proteins called GLUT transporters.

Non-facilitated diffusion

Non-facilitated diffusion is a physical process in which molecules move across a membrane. This process does not use covalent bonds and proceeds down a gradient of concentration or chemical potential. In addition, the process is spontaneous. It occurs when a ligand is transported from one cell to another without the aid of a receptor. Passive diffusion, by contrast, is slow and requires a receptor. It is slowed down by the presence of a cell membrane composed of highly charged molecules.

In contrast, facilitated diffusion uses a protein carrier to transport substances. A molecule called a channel protein binds to a molecule’s surface and then causes the molecule to pass across the membrane. This causes the molecule to undergo a conformational change and moves it to the cell’s interior, depending on the concentration gradient. Because carrier proteins are bulky, it is unlikely they can diffuse the solute, but they do accomplish the task of transporting it.

Molecular diffusion

Molecular diffusion is a process by which molecules move in a liquid or gas. When the energy of a molecule is high enough, the molecule breaks a bond with its neighbour, allowing it to move. Liquids have a smaller intermolecular spacing than gases, making diffusion in liquids possible even at low pressure. Temperature also increases intermolecular spacing and enhances diffusion.

Molecular diffusion plays a key role in high-performance liquid chromatography. To optimize column performance, molecular diffusion coefficients are vital. There are various experimental and correlation-based methods for determining molecular diffusion coefficients. The Wilke-Chang equation, Reddy-Doraiswamy equation, and Hayduk-Laudie equation are all useful in determining molecular diffusion coefficients.

Trace element diffusion

Trace element diffusion coefficients are estimates of a specific molecule’s diffusion rate. They are calculated from chemical sorption data and can be used to compare two different molecules in a solution. The results show heavier elements are more resistant to diffusion than lighter ones. For a given concentration, the diffusion coefficient of a specific molecule depends on two factors, namely its initial concentration and its final concentration.

Trace element diffusion is a critical consideration in archaeological research. By measuring the levels of trace elements in archaeological remains, researchers can estimate the length of burial and determine paleodiets. Trace element concentrations in fossils can be used to estimate the redox conditions of early burial and the source of fossils. Fluorine diffuses faster than cations, and its concentration is controlled by bioapatite, which acts as a sink for the element.

Molecular diffusion in solids

Diffusion is a process that allows molecules to move from one area to another within a solid. It occurs in several fields, including chemical reactions and human absorption. Albert Einstein wrote extensively about this phenomenon and linked it to the Brownian motion of atoms. It results in a uniform distribution of molecules and can limit the speed of industrial processes and distillation.

Molecular diffusion can occur in solids, gases, and liquids. It happens because the random motion of molecules within a material is thermally activated. This causes atoms to vibrate and move from areas of high concentration to areas with low concentrations until the concentrations are equal.

Molecular diffusion in gases

Molecular diffusion is the process by which molecules in a gas move around and disperse in a closed container. This process is influenced by temperature, pressure, and total molar density. The higher the temperature, the faster the diffusion. Higher temperatures reduce collisions and lengthen free paths, resulting in faster diffusion.

The rate of diffusion is measured in moles per square meter per second. It is proportional to the driving force, which is usually a concentration gradient. For example, when two gases, A and B, have the same molar volume, their diffusion rates must be equal or opposite. Similarly, the diffusion rate depends on the medium’s temperature, shape, and viscosity.

Molecular diffusion in liquids

Molecular diffusion is the process by which molecules move from one part of a system to another. The process produces a dynamic equilibrium and complete mixing of the system. Molecular diffusion occurs because of the interaction between molecules and the concentration gradients of all chemical species in a system. In liquids, it can happen due to the interactions between molecules of the same species.

Molecular diffusion occurs in all systems and is often the rate-limiting reaction process. It is also the ultimate mechanism for homogenization, mixing, and dilution of substances.