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What is the subject Physical Chemistry?

Physical chemistry is a branch of chemistry concerned with interactions and transformations of materials. It lies at the interface of chemistry and physics, in as much as it draws on the principles of physics (especially quantum mechanics) to account for the phenomena of chemistry. Unlike other branches, it deals with the principles of physics underlying all chemical interactions (e.g., gas laws), seeking to measure, correlate, and explain the quantitative aspects of reactions.

Quantum mechanics has clarified much for physical chemistry by modeling the smallest particles ordinarily dealt with in the field, atoms and molecules, enabling theoretical chemists to use computers and sophisticated mathematical techniques to understand the chemical behaviour of matter.

Chemical thermodynamics deals with the relationship between heat and other forms of chemical energy, kinetics with chemical reaction rates. Subdisciplines of physical chemistry include electrochemistry, photochemistry (see photochemical reaction), surface chemistry, and catalysis.

Why is Physical Chemistry important?

Physical chemistry is essential to understanding the other branches of chemistry. It provides a basis for understanding the thermodynamic influences (principally, the entropy changes accompanying reactions) that drive chemical reactions forward. It provides justifications for the schemes proposed in organic chemistry to predict and account for the reactions of organic compounds.

It accounts for the structures and properties of transition metal complexes, organometallic compounds, the microporous materials known as zeolites that are so important for catalysis, and biological macromolecules, such as proteins and nucleic acids, including DNA.

What are the branches of Physical Chemistry?

Physical chemistry is traditionally divided into a number of disciplines, but the boundaries between them are imprecise.

Thermodynamics is the study of transformations of energy. Although this study might seem remote from chemistry, in fact it is vital to the study of how chemical reactions yield work and heat. Thermodynamic techniques and analyses are also used to elucidate the tendency of physical processes (such as vaporisation) and chemical reactions to reach equilibrium —the condition when there is no further net tendency to change. Thermodynamics is used to relate bulk properties of substances to each other, so that measurements of one may be used to deduce the value of another.

Theoretical chemistry is a branch of physical chemistry in which quantum mechanics and statistical mechanics are used to calculate properties of molecules and bulk systems. The greater part of activity in quantum chemistry, as the former is commonly termed, is the computation of the electronic structures of molecules and, often, their graphical representation. This kind of study is particularly important to the screening of compounds for potential pharmacological activity, and for establishing the mode of action of enzymes.