In science, we look for patterns to discover nature’s laws. What is the pattern common to all spontaneous changes? To find a pattern, it is often best to start with very simple examples, because then the pattern is likely to be more obvious. So let’s think about two simple spontaneous changes — the cooling of a hot metal and the expansion of a gas — at a molecular level and search for their common feature.

A hot block of metal cools as the energy of its vigorously vibrating atoms spreads into the surroundings. The vigorously moving atoms of the metal collide with the slower atoms and molecules of the surroundings, transferring some of their energy in the collisions. The reverse change is very improbable, because it would require that energy migrate from the surroundings and concentrate in a small block of metal. Such a process would require that collisions of the less vigorously moving atoms of the surroundings with the more vigorously moving atoms of the metal would cause the latter to note even more vigorously. The randomly moving molecules of a has spread out all over their container; it is very unlikely that their random motion will bring them all simultaneously back into one corner. The pattern starting to emerge is that energy and matter tend to disperse in a disorderly fashion.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

## Rayleigh- Jean’s Law

Lord Rayleigh on classical limes made an attempt to explain the energy distribution in black body radiation, which was completed by Jeans in 1900. The result obtained by then is known as Rayleigh – Jean’s Law. Black body emits radiation of continuously variable wavelength right from zero to infinity. This radiation can be imagined as broken up into monochromatic waves.…

## The Lindemann Theory of Unimolecular Reactions

[ Also known as Lindemann-Hinshelwood mechanism.] It is easy to understand a bimolecular reaction on the basis of collision theory. When two molecules A and B collide, their relative kinetic energy exceeds the threshold energy with the result that the collision results in the breaking of comes and the formation of new bonds. But how can one account for a…

## Albert Einstein and His introduction to the Concept of Relativity

Albert Einstein This name need not be explained. Albert Einstein is considered to be one of the best physicists in the human history. The twentieth century has undoubtedly been the most significant for the advance of science, in general, and Physics, in particular. And Einstein is the most luminated star of the 20th century. He literally created cm upheaval by…

## Consequences of Light Absorption – The Jablonski Diagram

All about the Light Absorption’s theory on the basis of Jablonski diagram. According to the Grotthus – Draper Law of photo-chemical activation: Only that light which is absorbed by a system, can bring a photo-chemical change. However it is not true that all the kind of light(s) that are absorbed could bring a photo-chemical change. The absorption of light may result in…

## Classical Theory of Raman Scattering

The classical theory of Raman effect, also called the polarizability theory, was developed by G. Placzek in 1934. I shall discuss it briefly here. It is known from electrostatics that the electric field $E$ associated with the electromagnetic radiation induces a dipole moment $mu$ in the molecule, given by $\mu = \alpha E$ …….(1)…

## What you need to write better chemistry notes (and what not)?

Chemistry is one strange subject. It begins with a simple substance and goes above complex polymers – and, down to subatomic particles. I have been writing a lot recently on how to read, revise and make notes etc., to help you become a better student. Class notes aren’t always the best solution and if you are aspiring to become a…