Unisa my. UNISA e Bookshop. EBookshop List Welcome to the eBookshop service. Only Unisa students with valid student numbers can advertise bookshop items. Students who have joined myUnisa must. Diffusion Wikipedia. A diffusion is a process in physics. Some particles are dissolved in a glass of water. I/41J7pq9tEDL.jpg' alt='Applied Mathematics 3Rd Edition Malik' title='Applied Mathematics 3Rd Edition Malik' />At first, the particles are all near one corner of the glass. If the particles randomly move around diffuse in the water, they eventually become distributed randomly and uniformly from an area of high concentration to an area of low concentration, and organized diffusion continues, but with no net flux. Time lapse video of diffusion of a dye dissolved in water into a gel. Diffusion from a microscopic and macroscopic point of view. Initially, there are solute molecules on the left side of a barrier purple line and none on the right. Applied Mathematics 3Rd Edition Malik' title='Applied Mathematics 3Rd Edition Malik' />The concept of diffusion is widely used in physics particle diffusion, chemistry, biology, sociology, economics, and finance diffusion of people, ideas and of. Looking for books on Abstract Algebra Check our section of free ebooks and guides on Abstract Algebra now This page contains list of freely available Ebooks. The barrier is removed, and the solute diffuses to fill the whole container. Top A single molecule moves around randomly. Middle With more molecules, there is a statistical trend that the solute fills the container more and more uniformly. Bottom With an enormous number of solute molecules, all randomness is gone The solute appears to move smoothly and deterministically from high concentration areas to low concentration areas. There is no microscopic force pushing molecules rightward, but there appears to be one in the bottom panel. This apparent force is called an entropic force. Three dimensional rendering of diffusion of purple dye in water. Diffusion is the net movement of molecules or atoms from a region of high concentration or high chemical potential to a region of low concentration or low chemical potential. This is also referred to as the movement of a substance down a concentration gradient. A gradient is the change in the value of a quantity e. For example, a change in concentration over a distance is called a concentration gradient, a change in pressure over a distance is called a pressure gradient, and a change in temperature over a distance is a called a temperature gradient. The word diffusion derives from the Latin word, diffundere, which means to spread out a substance that spreads out is moving from an area of high concentration to an area of low concentration. A distinguishing feature of diffusion is that it dependends on particle random walk, and results in mixing or mass transport without requiring directed bulk motion. Bulk motion bulk flow is the characteristic of advection. The term convection is used to describe the combination of both transport phenomena. Diffusion vs. bulk floweditAn example of a situation in which bulk motion and diffusion can be differentiated is the mechanism by which oxygen enters the body during external respiration breathing. The lungs are located in the thoracic cavity, which expands as the first step in external respiration. This expansion leads to an increase in volume of the alveoli in the lungs, which causes a decrease in pressure in the alveoli. This creates a pressure gradient between the air outside the body relatively high pressure and the alveoli relatively low pressure. The air moves down the pressure gradient through the airways of the lungs and into the alveoli until the pressure of the air and that in the alveoli are equal i. The air arriving in the alveoli has a higher concentration of oxygen than the stale air in the alveoli. The increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli. Oxygen then moves by diffusion, down the concentration gradient, into the blood. The other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases. This creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli, as fresh air has a very low concentration of carbon dioxide compared to the blood in the body. International Journal of Engineering Research and Applications IJERA is an open access online peer reviewed international journal that publishes research. Please click the following link to download and install When you are finished installing, please return to this window and PRESS F5 to view this edition. The pumping action of the heart then transports the blood around the body. As the left ventricle of the heart contracts, the volume decreases, which increases the pressure in the ventricle. This creates a pressure gradient between the heart and the capillaries, and blood moves through blood vessels by bulk flow down the pressure gradient. As the thoracic cavity contracts during expiration, the volume of the alveoli decreases and creates a pressure gradient between the alveoli and the air outside the body, and air moves by bulk flow down the pressure gradient. Diffusion in the context of different disciplineseditThe concept of diffusion is widely used in physics particle diffusion, chemistry, biology, sociology, economics, and finance diffusion of people, ideas and of price values. However, in each case, the object e. There are two ways to introduce the notion of diffusion either a phenomenological approach starting with Ficks laws of diffusion and their mathematical consequences, or a physical and atomistic one, by considering the random walk of the diffusing particles. Ivona Voices Crack. G5 Games For Android more. In the phenomenological approach, diffusion is the movement of a substance from a region of high concentration to a region of low concentration without bulk motion. According to Ficks laws, the diffusion flux is proportional to the negative gradient of concentrations. It goes from regions of higher concentration to regions of lower concentration. Some time later, various generalizations of Ficks laws were developed in the frame of thermodynamics and non equilibrium thermodynamics. Best Flv Video Player. From the atomistic point of view, diffusion is considered as a result of the random walk of the diffusing particles. In molecular diffusion, the moving molecules are self propelled by thermal energy. Random walk of small particles in suspension in a fluid was discovered in 1. Robert Brown. The theory of the Brownian motion and the atomistic backgrounds of diffusion were developed by Albert Einstein. The concept of diffusion is typically applied to any subject matter involving random walks in ensembles of individuals. Biologists often use the terms net movement or net diffusion to describe the movement of ions or molecules by diffusion. For example, oxygen can diffuse through cell membranes so long as there is a higher concentration of oxygen outside the cell. However, because the movement of molecules is random, occasionally oxygen molecules move out of the cell against the concentration gradient. Because there are more oxygen molecules outside the cell, the probability that oxygen molecules will enter the cell is higher than the probability that oxygen molecules will leave the cell. Therefore, the net movement of oxygen molecules the difference between the number of molecules either entering or leaving the cell is into the cell. In other words, there is a net movement of oxygen molecules down the concentration gradient. History of diffusion in physicseditIn the scope of time, diffusion in solids was used long before the theory of diffusion was created. For example, Pliny the Elder had previously described the cementation process, which produces steel from the element iron Fe through carbon diffusion. Another example is well known for many centuries, the diffusion of colours of stained glass or earthenware and Chinese ceramics. In modern science, the first systematic experimental study of diffusion was performed by Thomas Graham. He studied diffusion in gases, and the main phenomenon was described by him in 1. The measurements of Graham contributed to James Clerk Maxwell deriving, in 1. CO2 in air. The error rate is less than 5. In 1. 85. 5, Adolf Fick, the 2. Zrich, proposed his law of diffusion.