Chemistry

Chemistry is the science of matter: its composition, structure, properties and the changes it undergoes during reactions. It explains why substances behave as they do by examining the atoms and molecules that make them up and the ways those particles combine, rearrange and exchange energy. The field is traditionally divided into branches that study different classes of substance and different kinds of question.

The foundation is atomic structure and chemical bonding. Atoms consist of a dense nucleus of protons and neutrons surrounded by electrons, and it is chiefly the arrangement of electrons that determines how atoms join together, whether by sharing electrons in covalent bonds or by transferring them to form ions. Inorganic chemistry deals largely with compounds not based on carbon chains, including many reactions in which electrons are transferred, known as redox or oxidation-reduction reactions. Physical chemistry applies the laws of physics to chemical systems, studying topics such as the rates of reactions and how catalysts speed them up, and the conditions of chemical equilibrium, where forward and reverse reactions proceed at equal rates.

Equilibrium concepts extend to redox equilibria and to acid-base equilibria, which govern how acids and bases behave in solution. Instrumental analysis provides the methods chemists use to identify and measure substances: mass spectrometry sorts particles by mass to reveal composition, infrared spectroscopy probes molecular vibrations to identify chemical groups, and nuclear magnetic resonance reveals the arrangement of atoms within a molecule. Organic chemistry, the study of carbon compounds, draws these ideas together to explain the vast range of molecules found in living things and synthetic materials.

Frequently asked questions

What is the difference between organic and inorganic chemistry?

Organic chemistry studies carbon-based compounds, especially those with chains and rings of carbon atoms, while inorganic chemistry covers most other elements and compounds, including metals and minerals.

What is chemical equilibrium?

Chemical equilibrium is the state in which the forward and reverse reactions occur at equal rates, so the concentrations of reactants and products remain constant over time.

How does instrumental analysis identify a substance?

Techniques such as mass spectrometry, infrared spectroscopy and nuclear magnetic resonance each probe a different property, allowing chemists to deduce a compound's composition and structure.