Physical chemistry

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Not to be confused with Physiological chemistry or Chemical physics.
Between the flame and the flower is aerogel, whose synthesis has been aided greatly by physical chemistry.
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Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mechanics, analytical dynamics and chemical equilibria.

Physical chemistry, in contrast to chemical physics, is predominantly (but not always) a supra-molecular science, as the majority of the principles on which it was founded relate to the bulk rather than the molecular or atomic structure alone (for example, chemical equilibrium and colloids).

Some of the relationships that physical chemistry strives to understand include the effects of:

  1. Intermolecular forces that act upon the physical properties of materials (plasticity, tensile strength, surface tension in liquids).
  2. Reaction kinetics on the rate of a reaction.
  3. The identity of ions and the electrical conductivity of materials.
  4. Surface science and electrochemistry of cell membranes.[1]
  5. Interaction of one body with another in terms of quantities of heat and work called thermodynamics.
  6. Transfer of heat between a chemical system and its surroundings during change of phase or chemical reaction taking place called thermochemistry
  7. Study of colligative properties of number of species present in solution.
  8. Number of phases, number of components and degree of freedom (or variance) can be correlated with one another with help of phase rule.
  9. Reactions of electrochemical cells.
  10. Behaviour of microscopic systems using quantum mechanics and macroscopic systems using statistical thermodynamics.
  11. Calculation of the energy of electron movement in molecules and metal complexes.

Key concepts

The key concepts of physical chemistry are the ways in which pure physics is applied to chemical problems.

One of the key concepts in classical chemistry is that all

chemical reactions can be described as the making and breaking of those bonds. Predicting the properties of chemical compounds from a description of atoms and how they bond is one of the major goals of physical chemistry. To describe the atoms and bonds precisely, it is necessary to know both where the nuclei of the atoms are, and how electrons are distributed around them.[2]

Disciplines

Quantum chemistry, a subfield of physical chemistry especially concerned with the application of quantum mechanics to chemical problems, provides tools to determine how strong and what shape bonds are,[2] how nuclei move, and how light can be absorbed or emitted by a chemical compound.[3] Spectroscopy is the related sub-discipline of physical chemistry which is specifically concerned with the interaction of electromagnetic radiation with matter.

Another set of important questions in chemistry concerns what kind of reactions can happen spontaneously and which properties are possible for a given chemical mixture. This is studied in

quasi-equilibrium and non-equilibrium thermodynamics can describe irreversible changes.[5] However, classical thermodynamics is mostly concerned with systems in equilibrium and reversible changes
and not what actually does happen, or how fast, away from equilibrium.

Which reactions do occur and how fast is the subject of

catalysts
in the reaction mixture, as well as how catalysts and reaction conditions can be engineered to optimize the reaction rate.

The fact that how fast reactions occur can often be specified with just a few concentrations and a temperature, instead of needing to know all the positions and speeds of every molecule in a mixture, is a special case of another key concept in physical chemistry, which is that to the extent an engineer needs to know, everything going on in a mixture of very large numbers (perhaps of the order of the Avogadro constant, 6 x 1023) of particles can often be described by just a few variables like pressure, temperature, and concentration. The precise reasons for this are described in statistical mechanics,[8] a specialty within physical chemistry which is also shared with physics. Statistical mechanics also provides ways to predict the properties we see in everyday life from molecular properties without relying on empirical correlations based on chemical similarities.[5]

History

See also: History of chemistry
Fragment of M. Lomonosov's manuscript 'Physical Chemistry' (1752)

The term "physical chemistry" was coined by

Petersburg University.[9]
In the preamble to these lectures he gives the definition: "Physical chemistry is the science that must explain under provisions of physical experiments the reason for what is happening in complex bodies through chemical operations".

Modern physical chemistry originated in the 1860s to 1880s with work on

Gibbs' phase rule.[10]

The first

Svante August Arrhenius,[11] these were the leading figures in physical chemistry in the late 19th century and early 20th century. All three were awarded the Nobel Prize in Chemistry
between 1901 and 1909.

Developments in the following decades include the application of

surface chemistry, where Irving Langmuir made many contributions. Another important step was the development of quantum mechanics into quantum chemistry from the 1930s, where Linus Pauling was one of the leading names. Theoretical developments have gone hand in hand with developments in experimental methods, where the use of different forms of spectroscopy, such as infrared spectroscopy, microwave spectroscopy, electron paramagnetic resonance and nuclear magnetic resonance spectroscopy
, is probably the most important 20th century development.

Further development in physical chemistry may be attributed to discoveries in nuclear chemistry, especially in isotope separation (before and during World War II), more recent discoveries in astrochemistry,[12] as well as the development of calculation algorithms in the field of "additive physicochemical properties" (practically all physicochemical properties, such as boiling point, critical point, surface tension, vapor pressure, etc.—more than 20 in all—can be precisely calculated from chemical structure alone, even if the chemical molecule remains unsynthesized),[citation needed] and herein lies the practical importance of contemporary physical chemistry.

See

Group contribution method, Lydersen method, Joback method, Benson group increment theory, quantitative structure–activity relationship

Journals

Main category: Physical chemistry journals

Some journals that deal with physical chemistry include

Historical journals that covered both chemistry and physics include Annales de chimie et de physique (started in 1789, published under the name given here from 1815 to 1914).

See also

References

  1. ISBN 0-8247-1922-0
    .
  2. ^
    ISBN 0-19-927498-3
    .
  3. ISBN 0-19-927498-3
    .
  4. ISBN 0-7506-3372-7
    .
  5. ^
    ISBN 0-486-65242-4
    .
  6. ISBN 0-19-516925-5
    .
  7. ISBN 0-19-516925-5
    .
  8. ISBN 978-0-19-504277-1
    .
  9. ISBN 0-8047-0738-3
    .
  10. ^ Josiah Willard Gibbs, 1876, "On the Equilibrium of Heterogeneous Substances", Transactions of the Connecticut Academy of Sciences
  11. ISBN 0-19-855919-4
    .
  12. PMID 16833724
    .
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