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# Physical Chemistry

Physical chemistry involves both the study of physics and chemistry. Physics has been defined as the study of the properties of matter that are shared by all substances. Whereas, chemistry has been defined as the study of properties of individual substances.

What is Physical Chemistry?

It is the study of the underlying physical principles that govern the properties and behavior of chemical systems.

Physical chemistry for the life sciences applies the principles, practices and concepts of physics in chemistry.

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## Thermochemistry

This branch of chemistry which deals with the study of energy changes accompanying chemical reactions is termed as thermochemistry.

## Electrochemistry

Electrochemistry can be defined as the science concerned with the mutual transformation of chemical and electrical energy. It deals with the structure of electrolyte solutions as well as with the phenomena occurring at the interfaces between metallic electrodes and electrolyte solutions.

## Colloidal Chemistry

This branch of chemistry deals with the nature and composition of colloids. It deals with the substance which exists as a suspension in a continuous medium, especially a liquid, solid, or gaseous substance.

## Quantum Mechanics

Quantum chemistry is a branch of theoretical chemistry, which applies quantum mechanics and quantum field theory to address problems in chemistry.

## Physical Chemistry a Molecular Approach

Physical chemistry can be described as a set of characteristically quantitative approaches to the study of chemical problems. For example, in the study of thermodynamics and rates of chemical reactions, we employ a phenomenological, macroscopic approach. But a microscopic , molecular approach is necessary to understand the kinetic behavior of molecules and reaction mechanisms. Ideally we study all phenomena at the molecular level because that is where change occur.

## Principles of Physical Chemistry

Physical chemistry is a branch of chemistry concerned with the properties and reactions of chemistry based on the physical laws governing the motion and energy of the atoms and molecules involved. The field of physical chemistry is highly mathematical and also involves physics. Chemists who explore this field utilize many fundamental principles of chemistry.

## Physical Chemistry Equations

Physical chemistry is a quantitative science which implies that equations will frequently be given. It may be useful to point out that equations can be of various types. Some equations define a property like "pressure equals force over area." The equation numbers of equations important enough to memorize are starred.

Physical chemistry provides quantitative relations for a great number of phenomena encountered in chemistry, based on well defined and measurable properties.

Physical chemistry is the study of the physical basis of phenomena related to the chemical composition and structure of substances. Physical chemistry is the branch of chemistry that develop theoretical and mathematical explanations for chemical behavior. Physical chemists use advanced mathematics and computers to model the behavior of atoms and molecules, and their research has allowed chemists to produce new compounds with desired properties.

Advances in physical chemistry are used in modeling all types of combustion reactions such as fires, explosions, coal fired power plants and internal combustion engines.

## Physical Chemistry of Surfaces

The chemistry of surfaces and interfaces plays dominating roles in our lives. The challenge of modern physical chemistry is to understand macroscopie surface phenomena on the molecular level.

Since the early 1960s techniques for the study of surfaces on the molecular level which provided the foundation for the rapid evolution of surface science, have become available in over increasing numbers.

## Physical Chemistry Topics

Physical chemistry is the study of the physical and fundamental base of chemical systems and processes. Important topics of Physical Chemistry include:

## States of Matter

All the material on earth exist in three different states: solid, liquid and gas. Matter is made up of tiny particles called atoms. Every solid, liquid and gas in the universe has atoms. Atoms are so small and it is not visible to eyes. Atoms consist of three parts composed of protons, neutrons and electrons.

The elements of physical chemistry directly determines the types of interactions it has with other elements and thus the sorts of chemical and bio chemical functions that element can perform for the organism.

## Chemical Change and Chemical Systems

The observation of chemical reaction is generalized in certain way called laws of chemical change. There are several types of chemical changes including synthesis, decomposition, single displacement, double displacement, neutralization, precipitation, combustion and redox reaction.

## Conservation of Matter and Stoichiometry

In the context of ecological Stoichiometry, conservation of energy presents somewhat of a semantic problem. The term Stoichiometry normally refers only to the conservation of matter.

## Chemical Kinetics

Chemical kinetics is also known as reaction kinetics. Kinetics can be subdivided into physical kinetics, dealing with physical phenomena such as diffusion and viscosity, and chemical kinetics which deals with the rates of chemical reaction.

## Kinetic Theory of Gases

This is the study of action of molecules. Gases can be studied based on the relationship among the temperature, pressure and volume of gases. According to this theory, energy and momentum are conserved in all collisions between particles, and the average behavior of the particles can be deduced by statistical analysis.

## Thermodynamics

The branch of physical science that deals with the relations between heat and other forms of energy and by extension of the relationships and inter convertibility of all forms of energy.

## Physical Chemistry Problems

Some of the solved problems in physical chemistry is shown below.

### Solved Examples

Question 1: What are the concentrations of all species in pure water?
Solution:

Mass balance: [Na+] = 0, [HOAc] = 0, [OAc-] = 0
Charge balance: [H+] = [OH-]
Equilibrium: [H+][OH-] = 1.0 $\times$ 10-14

Therefore

[H+]2 = 1.0 $\times$ 10-14
[H+] = 1.0 $\times$ 10-7
[OH-] = 1.0 $\times$ 10-7

Question 2: Ice crystallizes in a hexagonal lattice having volume of unit cell as 132 $\times$ 10-24cm3. If the density is 0.92g cm-3 at given temperature. What is the number of H2O molecules per unit cell?
Solution:

$d = \frac{ZM}{N_{A}a^{3}} g cm^{-3}$
or $Z = \frac{dN_{A}V}{M}$

= $\frac{0.92 \times 132 \times 10^{-24} \times 6.02 \times 10^{23}}{18}$
= 4.06 = 4

 More topics in  Physical Chemistry States of Matter Physical and Chemical Changes Stoichiometry Chemical Kinetics Kinetic Theory Thermodynamics Thermochemistry Electrochemistry Colloids Quantum Mechanics Chemical Equilibrium
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