Evidence of Particle Nature of Matter

Evidence of the Particle Nature of Matter

Brownian Motion:

Brownian motion is the irregular and constant motion of molecules. It is the rapid, constant, and irregular motion of tiny particles.

In 1827, Robert Brown first observed the direct effect of the movement of molecules. He was looking through a microscope at pollen particles in water. To his surprise, he found that these particles were in continual haphazard motion.

Many years later, it was realized that the random motion of these particles was caused by bombardment from moving water molecules. The same kind of motion is shown by smoke particles suspended in air. This random motion is called Brownian motion, named after its discoverer, who was a botanist.

Brownian motion is important for two reasons. Firstly, it gives evidence for the existence of tiny particles of matter called molecules. Secondly, it gives evidence that these molecules are not still but in a constant state of random motion. Brownian motion also takes place in liquids and solids. In fact, Robert Brown first observed such motion while examining pollen grains in water under a microscope. Here, the motion is due to the bombardment of the solid particles by the water molecules. Molecules in solids such as camphor are able to leave the solid and spread into the air and to our nostrils, where their presence can be detected.

Law of Definite Proportion:

Another evidence in favor of the particle nature of matter was obtained from the analysis of chemical reactions. This crucial piece of evidence is known in chemistry as the law of definite proportions, which states that when two or more elements combine to form a compound, they always do so in the same proportions by weight.

Diffusion:

When hydrogen sulphide gas