Brownian Motion vs Diffusion
Brownian motion and diffusion are two concepts associated with the movement of particles. Existence of these two concepts proves that the matter is composed of smaller particles, which can be separated from each other. It also proves that there is enough free space between the atoms or molecules within a substance (solid, gas or a liquid) which allows other particles to travel through them.
What is Brownian Motion?
The botanist Robert Brown presented the concept of Brownian motion in 1827. He observed pollen grains in water under a microscope and saw that the pollen grains are moving here and there (random movement) in water. This movement was named as the Brownian motion. The explanation of this movement was given by Einstein. In his explanation, he describes some properties of atoms. Though, they believed the existence of atoms at that time, there was no proves for it. Brownian motion is a proof for the existence of atoms. Every matter around us is made from atoms. So even the pollen grains and water are made up of atoms. Einstein described that the movement of the pollen grain is due to its collisions with the water molecules which we can’t see. When water molecules hit the pollen grains it bounces off, and we can see it under the microscope. Since, we can’t see the water molecules; we tend to think that the pollen grains are moving on their own. By studying the Brownian motion, we can predict about some of the properties of the water molecules such as their speed of movement. As in water, the particles in the air also show Brownian motion. For example, a dust particle in the air is moving around randomly due to the collisions with the gas molecules.
What is Diffusion?
Diffusion is the travelling of particles from a higher concentration to a lower concentration. In other words, diffusion is the movements of particles from the regions of higher chemical potential, to areas of lesser chemical potential. So this concept is similar to the travelling of heat from a hot object to a cooler object. Osmosis is a type of diffusion that describes the movement of water. When water is moving from one cell to another, it flows according to a water potential gradient that is from a high water potential to a low water potential. Diffusion is an important concept in biological systems. Plants and animals absorb and distribute most of the nutrients, gases and water through diffusion. For instance, inside a cell, the oxygen content is lower than in blood capillaries, and the carbon dioxide concentration is higher than in the blood capillaries. Therefore, by diffusion oxygen is transferred into a cell from blood capillaries, and carbon dioxide is transferred out from the cell.
What is the difference between Brownian Motion and Diffusion?
• In Brownian motion, a particle does not have a specific direction to travel. Instead, it will move in all directions. But in diffusion the particles will travel from a high concentration to a low concentration. Therefore, they have a direction. However, the particle movement is random in both scenarios.
• Diffusion takes place according to a concentration or chemical potential gradient. But Brownian motion is not governed by such factors. Brownian motion of a particle is governed by the other particles in the medium.