The Brownian movement is named after Robert Brown, a Scottish botanist who was the first to study these vibrations (1827). Brown was looking into the pollen grain fertilisation of a newly found species of flowering plants when he spotted a fast rhythmic movement of microparticles inside the pollen grains held in liquid underneath the microscope. While Brown wasn’t the first to notice the occurrence, he was the first to investigate it thoroughly. Brownian movement in chemistry is the unpredictable or uncontrollable movement of particles within liquids or gases as a result of frequent interactions with other quick tiny particles. This is determined by particle size as well as the colloid’s viscosity.

Brownian movement meaning

1: Particle size is inversely proportional to the Brownian movement speed; small particles move faster as the angular motion is inversely proportional to particle mass. 

2: The less viscous a liquid, the faster the Brownian movement. Viscosity is a measure of the magnitude of a liquid’s internal friction. It is a measure of a fluid’s resistance to flow.

Effects of Brownian movement

1: Owing to Brownian movement, fluid particles are in constant motion. Particles cannot settle, resulting in the stabilisation of colloidal solutions.

2: This motion can differentiate true solutions from colloidal solutions.

Difference between Brownian movement and diffusion

• Brownian movement is the random and irregular motion of molecules. As stated in kinetic molecular theory, the direction of motion of molecules is random. Velocity is governed by temperature, which is a measure of the system’s kinetic energy.

• Diffusion is a statistically observed phenomenon due to Brownian motion. The random movement of molecules ensures that a molecule will move from its starting point to reach a point far away gradually but in a zig-zag motion. 

The statistics appear when you look at molecules in large numbers:

• Imagine a drop of dye in water. It first localises in a small area and then diffuses outwards, even assuming that the energy input into the system from the dye injection is not much.
• Each dye molecule moves in a random direction, and since there are more microparticles (possibly where the dye molecule might be located) than a local spot of the dye, it will diffuse. This is the idea of ​​entropy.

Einstein’s theory of Brownian movement

Since higher temperatures also lead to faster Brownian movement, in 1877, it was suggested that its cause lies in “thermal molecular motion in a liquid medium”. The idea that the molecules of a liquid or gas are in constant motion, colliding with each other and bouncing back and forth, was an important part of the kinetic theory of gases developed in the third quarter of the 19th century. 

• Physicists James Clerk Maxwell, Ludwig Boltzmann, and Rudolf Clausius explained the phenomenon of heat. Theoretically, the temperature of a substance is proportional to the average kinetic energy with which its molecules move or vibrate.
• It is, of course, conjectured that this motion could somehow be transmitted to larger particles that can be observed under a microscope; if true, it would be the first directly observed effect to support the kinetic theory.

In 1905, this reasoning led German physicist Albert Einstein to put forward his quantitative theory of Brownian movement. Similar studies of Brownian movement were conducted independently and almost simultaneously by Polish physicist Marian Smoluchowski, who used methods slightly different from those of Einstein. 

Conclusion

Albert Einstein’s paper on Brownian movement was important proof of the existence of atoms and molecules. The kinetic theory of gases explaining the pressure, temperature, and volume of gases is based on the Brownian model of the particles’ motion. The phenomenon has been determined to result from thermal molecular motion in environmental particles. In a liquid field, a suspended particle is bombarded by liquid molecules from all sides. If the particle is very small, the collisions it receives on one side will be stronger than those on the other side, causing it to jump. These small random jumps are known as Brownian motion.