Physical chemistry

Physical chemistry is a branch of chemistry dealing with the principles of physics in chemical interactions. It examines how matter behaves on a molecular and atomic level and how chemical reactions occur. Physical chemists seek to measure, correlate, and explain the quantitative aspects of reactions. Their discoveries are based on understanding chemical properties and describing their behavior using theories of physics and mathematical computations.

Physical chemists discover, test, and perform research to understand the physical characteristics of a material. To perform their work, they utilize sophisticated instrumentation and equipment such as lasers, mass spectrometers, nuclear magnetic resonance, and electron microscopes to analyze materials, develop methods to test and characterize the properties of materials, develop theories about these properties, and identify potential uses of materials.

The following are subdisciplines of physical chemistry:

• Thermodynamics—the study of the relationship between heat, work, temperature, and energy
• Chemical kinetics—the understanding of the rate of chemical reactions
• Photochemistry—a field related to the chemical effects of light
• Quantum chemistry—the application of quantum mechanics to chemistry
• Electrochemistry—the study of electron movement (electricity) due to chemical processes
• Material chemistry—also known as solid-state chemistry, the study of structure, synthesis, and properties of materials
• Biophysical chemistry—the application of physics and chemistry concepts to research biological systems
• Spectroscopy—the study of the interaction of electromagnetic radiation with matter
• Physical organic chemistry—a branch related to organic chemistry, focusing on the relationship between chemical structures and reactivity.

Before the scientific revolution of the sixteenth through to eighteenth centuries, all the natural sciences were grouped together using the phrase "natural philosophy." By 1800, separate disciplines, with distinct subject matters and investigative methods were becoming apparent. During the later nineteenth century, it became clear that discoveries in one science often had major consequences for another, and many scientists sought to recover the pre-scientific revolution unity between the sciences. A result of this was the rise of "physical chemistry," a field uniting ideas and techniques from both physics and chemistry. The term “physical chemistry” was introduced by Russian scientist Mikhail Lomonosov in 1752 during his lecture “A Course in True Physical Chemistry.”

The formal establishment of physical chemistry as a distinct field of science is typically attributed to Jacobus Van't Hoff (1852-1911), Svante Arrhenius (1859-1927), and Wilhelm Ostwald (1853-1932). In 1884 Van't Hoff published groundbreaking research on the behavior of solute particles in solutions. The same year, Svante Arrhenius completed a doctoral dissertation in which he argued electrolysis could be explained by assuming individual ions carry specific units of electrical charge. Ostwald's work between 1876 and 1884 showed that physical properties of solutions, particularly the heat of reactions and electrical conductivity, could be used to calculate the speed and degree of completion in chemical reactions.

Ostwald read Arrhenius's dissertation and Van't Hoff's book around the same time and realized their theories explained his own experimental results. Ostwald went on to establish contact with both of them. Arrhenius joined Ostwald's laboratory, and in 1887 Ostwald and Van't Hoff founded a new scientific periodical, the Zeitschrift für physikalische Chemie ("Journal of Physical Chemistry"), to propagate their research and views, with Ostwald as chief editor.

Key milestones in physical chemistry include the following:

• The development of infra-red spectroscopy by Sir Frederick William Herschel in 1800.
• Between 1842 and 1865 the first two laws of thermodynamics were formulated.
• In 1850 Alexander Williamson proposed a dynamic kinetic theory of chemical equilibrium.
• The development of microwave spectroscopy by James Clerk Maxwell in 1864
• Josiah Gibbs' work on the Gibbs energy and chemical potential published in his 1876 article titled “On the Equilibrium of Heterogeneous Substances.”
• Leading figures in physical chemistry in the late 19th century and early 20th Century Wilhelm Ostwald, Jacobus Van’t Hoff, and Svante Arrhenius creating the first scientific journal in the field of physical chemistry, "Zeitschrft fur Physikalische Chemie" (Journal of Physical Chemistry) in 1897.
• The development of quantum chemistry in the 1930s.
• The development of nuclear magnetic resonance by Edward Mills Purcell and Felix Bloch in 1940s
• The development of electron paramagnetic resonance by Yevgeny and Zavoisky in 1944
• The development of scanning tunneling microscopy spectroscopy by Gerd Binnig and Heinrich Rohrer in 1981