Physical chemistry

Chemistry is a branch of physical science that involves the study of the properties of matter—or anything that has mass, takes up space, and composes everything in life—and the ways in which substances interact with other substances and energy.

Physical chemistry combines chemistry with physics, a science that deals with matter and energy and their interactions. Physical chemistry encompasses the study of matter at the molecular and atomic levels and how this chemical structure affects the physical properties of a substance. An atom is the smallest unit of matter, while a molecule is a group of two or more atoms. The difference between the two is that a molecule can be broken down into atoms through chemical processes, while an atom is the smallest unit of an element that retains its chemical properties.

Overview

Russian scientist Mikhail Lomonosov coined the term physical chemistry in 1752. Since then, many advances have been made in the field. Physical chemists must be proficient in math and physics, and their work is similar to that of engineers. Chemists use physical chemistry to analyze materials, develop methods for testing materials, and determine the use of materials. Physical chemists aid many different industries; for example, they help the pharmaceutical, or drug, industry develop new drugs by determining how the human body will react to particular medications.

Chemists study several branches of physical chemistry, including thermodynamics, quantum chemistry, chemical kinetics, and statistical thermodynamics, to understand biological and chemical systems.

Thermodynamics

Thermodynamics deals with the relationship of heat to other forms of energy. In physical chemistry, thermodynamics refers to chemical reactions. It is governed by the laws of thermodynamics.

Heat can move, make atoms move, and increase energy. When the amount of heat in a system is increased, the amount of energy is also increased. Energy is constantly moving, but much of it happens on a small scale, such as at the atomic level. For example, atoms and molecules transmit energy. To move heat from one area to another, millions of atoms and molecules must work together to make this happen. Heat moves from one area to another because energy flows from a region of higher temperature to a region of lower temperature.

Energy transfer is caused by something that exerts a force. The first law of thermodynamics deals with the amount of energy in a system. According to the law, energy is constant and cannot be created or destroyed. It can, however, be transferred or converted. A change in the energy of a system will always be equal to the amount of heat introduced to or taken from a system minus the energy, or work (energy transferred by a force), the system has produced. For example, in a game of volleyball, when players hit the ball, they transfer force from their hands to the ball, causing the ball to move. In addition, variables such as pressure and temperature can alter this conversion process.

The second law of thermodynamics deals with entropy, or the measure of disorder or unavailable energy in a system. In the world, the amount of disorder is always increasing. Energy changes the freedom of molecules, or the ability for them to move around a system. When the state of a system is changed (for example, from solid to liquid to gas), the arrangements of atoms and molecules in the system are changed, meaning their ability to move around has increased. This change is entropy. As an example, think of a teenager’s disordered bedroom. It takes energy to clean and organize a bedroom, but it seems like it takes less energy for it to become unorganized.

Quantum Mechanics

Quantum mechanics deals with very small pieces of matter. It is concerned with how atoms and molecules bond to one another in systems. It was developed to help explain the atomic model. In the early 1900s, Danish physicist Niels Bohr contributed to atomic structure, but his research became outdated as scientists used principles of quantum field theory and quantum mechanics to study subatomic particles. German physicist Werner Heisenberg and the Austrian physicist Erwin Schrödinger helped develop quantum mechanics, which mathematically described how electrons behave as waves, thereby validating the concept of wave-particle duality.

Other Branches of Physical Chemistry

Chemical kinetics is the study of the rates of chemical processes, or how long these processes take to occur. Some processes take longer than others, and sometimes factors such as pressure and temperature can change the rate at which reactions occur. For example, the process of iron oxidation (such as metal rusting) occurs over a longer period than fuel combustion (the act of something burning).

Statistical thermodynamics deals with the distribution of energy in chemical systems. This branch of physical chemistry uses macroscopic properties of matter to understand interactions between microscopic properties such as molecules and particles. Other important branches of physical chemistry include electrochemistry, photochemistry, surface chemistry, and catalysis.

Bibliography

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