Chemistry and its Branches

Chemistry and its Branches

Definition of Chemistry
Science can be defined, as a never-ending search for truth and it is the system of knowledge, which is based on a set of facts, our understanding of those facts and verification of those facts by experiments. Thus science is the study of universe that deals with matter, energy, life and various aspects of life.

Chemistry is the "scientific study of matter, its properties, and interactions with other matter and with energy".

“Chemistry is the branch of science which deals with the study of composition, structure, properties (physical and chemical) and transformation of matter along with the chemical changes that occur in it.  It involves the study of physical and chemical changes that matter undergoes and the energy changes accompanying these changes. It also deals with laws and principles which govern these changes.”

The word chemistry is derived from the word “Kheem”, an old name of Egypt due to black colour of Egyptian soil. But some experts believed that the word chemistry came from the word “Chyma” meaning melt or cast. As the time passed on the word changed to Al-kimyain in Arabic and then to chemistry in English

Branches of Chemistry
The complete understanding and mastery over vast scientific knowledge is almost impossible. To facilitate the study of science, it has been subdivided into different disciplines. Chemistry, being a vast discipline of science has also been divided into a number of branches to facilitate its study. As our universe is an integrated unit so is its knowledge. There are no clear-cut boundaries between these branches. Chemists have made these divisions for the sake of their own convenience. All these branches of chemistry must deal with each other one way or another. If they did not work in unison it would be impossible for these chemistries to perform the functions we need for experiments. Thus all these branches of chemistry overlap each other. For example, one would not be able to measure the change in an organic or inorganic substance without knowing how to use analytical chemistry or without some proficiency in analytical chemistry. Chemistry can be divided into branches according to either the substances studied or the types of study conducted. The primary division of the first type is inorganic chemistry and organic chemistry and divisions of the second type are physical chemistry and analytical chemistry.

The chemistry has been divided into following nine main branches:

Physical Chemistry
It is the branch of chemistry that deals with the physical properties of substances and their dependence on chemical bonding. It deals with the forces and laws and principles governing the combination of atoms and molecules. It is especially concerned with energy changes in physical and chemical processes.

Inorganic Chemistry
It is that branch of chemistry that deals with the study of all elements and their compounds generally obtained from non-living or mineral origin. The detailed study of carbon compounds (or organic compounds) especially carbon-hydrogen compounds (hydrocarbons) and their derivatives are avoided in inorganic chemistry. However some carbon compounds like metal carbonates (CO32¯), bicarbonates (HCO3¯), cyanides (CN¯), thiocyanates (CNS¯), cyanates (CNO¯), carbides (C4¯), and oxides of carbon (CO and CO2) are studied in inorganic chemistry.

Organic Chemistry
With the exceptions of CO, CO2, metal carbonates, bicarbonates, cyanides, thiocyanates, cyanates and carbides, organic chemistry is the study of essentially all carbon compounds generally obtained from living organisms. In fact, it is the chemistry of hydrocarbons (carbon-hydrogen compounds) and their derivatives. Most of the consumer products are organic in nature.

Biochemistry
It is the branch of chemistry that deals with the compounds and their reactions (metabolism) in living organisms (i.e. in plants and animals). Biochemistry is the backbone of medical science.

Industrial Chemistry
It is the branch of chemistry that deals with the study of different chemical processes involved in the industry for the large scale manufacture of synthetic products like cement, glass, paper, fertilizers, soaps, detergents, medicines, plastics, paints, soda ash, caustic soda etc. Industrial chemistry helps us in the manufacturing of the industrial products and their uses. It is the application of chemical knowledge in technology and industry for preparation of industrial products on large scale.

Nuclear Chemistry
It deals with the changes occurring in the nuclei of atoms accompanied by emission of radiation. It also deals with the characteristics of radioactive processes both natural and artificial and atomic energy generated there.

Analytical Chemistry
It deals with the methods and techniques used to determine the kind and quantity of various components in a given substance.

Environmental Chemistry
It is the study of the interaction of various chemical materials and their effects on human environment. Pollution, personal hygiene and health hazards are important aspects of environmental chemistry.

Polymer Chemistry
It deals with the study of polymerization and the products obtained through the process of polymerization called polymers such as plastics like polyvinyl chloride (PVC), papers, synthetic fibers etc.

Importance of Branches of Chemistry

Chemistry also help us to understand the nature of our environment and about ourselves.The theories of chemistry illuminate our understanding of the material world from tiny atom to giant galaxies.

Chemistry plays a vital role in the modern world.  It has not only changed our standard of living but also has improved health conditions. Every branch of chemistry has its own importance in human life.

1.   Biochemistry is the backbone of medical science.

2.   Industrial chemistry helps us in manufacturing of industrial products

3.   Environmental chemistry tell us that how one can protect its environment from environmental hazards.

4.   Analytical chemistry is important to understand the composition of compounds, quality of products, analysis of biological samples (urine, blood, milk etc.)

5.   Nuclear chemistry gives atomic energy that can be used in various fields. It also provides us Radioisotopes for the treatment of many diseases such as cancer.

Chemistry and Society

There are three significant reasons to study chemistry:

Firstly; chemistry has important practical applications in the society.
Second; chemistry is an intellectual enterprise, a way of explaining our material world.
Third, chemistry figures prominently in other fields such as in biology, the advancement of medicines.

The role of chemistry in the prevailing society is of enormous benefits. We are familiar with many chemicals, which have become part and parcel of our daily life. Chemistry has deep influence on our daily living. It matters with the protection of environment, providing our everyday needs of food, clothing and shelters, giving pharmaceutical chemicals that enhance our health and prolong our lives. For instance, drugs or medicines to fight diseases, pesticides to protect our health and crops, fertilizers to grow our crops for abundant food, food, plastic, soap, detergents, cosmetics, cement, glass, synthetic fibres to provide comfort and variety in clothes, explosives are the major gifts of chemistry.  For example:

1.    Chlorine has become an essential commercial chemical and this single element is used for producing more than one thousand chlorine compounds of great industrial importance, such as polyvinyl chloride (PVC) as plastics for pipes. Other chlorine compounds are employed as bleaching agent, disinfectant, solvents, pesticides, refrigerant, flame retardant and drugs. Chlorine itself is used to kill all pathogenic (disease-causing) organisms, which causes cholera, typhoid fever and dysentery (water–borne diseases transmitted through impure drinking water).

2.  Fluoride compounds such as sodium fluoro phosphate (SnF2.Na2PO4.F) and NaF in our tooth pastes help to protect and control tooth decay and it is a great beneficence of chemistry on the society.


Landmarks in the History of Chemistry 
(Historical Back Ground of Chemistry)

Chemistry is as old as human civilization. Over the centuries chemistry has undergone remarkable progress. Chemistry from the very beginning was used in pottery making, glass making, dyeing and in metallurgy. The development of chemistry can be divided into following periods:

1.            The Greek Period                  
2.            Muslim or Al-chemical Period                    
3.            The Modern period

The Greek Period

Scientist of Greek period

1.            Plato                (347- 428 B.C)
2.            Aristotle           (322- 384 B.C)
3.            Democritus     (357- 460 B.C)
4.            Socrates         

Contribution of Greek period

1.   The Greek philosophers contributed a lot in number of small way to the early development of             chemistry. [The Greek philosophers were the first to develop ideas relating to chemistry].

2.   They introduced the concept of elements, atoms, shapes of atoms and chemical combination (reactions). The Greek philosopher Democritus in the 5th century put forward the idea that matter consisted of very small indivisible particles, which he named Atomos (nowadays called atoms).

3.   They believed that all matter was derived form four elements (components) i.e. earth, air, fire, and water. They also believed that the combination of these materials could produce new materials. According to them fire was hot and dry, earth was dry and cold, water was cold or hot and wet and air was cold or hot and wet.

4.   The Romans developed and improved metallurgical processes and enamellings of pottery.

Unfortunately, all these developments were empirical (experimental) and achieved by trial and error method without the basis of any systematic study. Greeks were basically philosophers believing in theoretical ideas and not in experimental confirmation of their ideas and thus they presented chemistry and science as a theoretical subject. Therefore, Chemistry could not develop and flourish during this period. [Thus many of the Greek principles proved wrong afterward for the same reason].

The Muslim Period

Scientists or Al-chemists of Muslim period

1.    Jabir Ibne- Haiyan                        (721-803 A.D)             
2.    Abu Baker Al-Zakaria Al-Razi      (862-930 A.D)             
3.    Al-Beruni                                       (973-1048 A.D)
4.    Abu Ali Ibne-Sina                          (980-1037 A.D)

Achievements of Muslim Period

1.   The period form 600-1600 A.D. in the history of chemistry is known as the period of alchemist. This is the period where foundation of modern science took place. The Muslim scientists made rich contributions to various branches of science. In-fact Muslims are the Torch Bearers of modern science.

2.   They made use of scientific methods and thus they treated and presented chemistry as an experimental science.

3.   The alchemists developed and used such laboratory equipments such as funnels, beakers, balances, scale for weighing, crucible for melting metals, retorts for distillation etc.

4.   They discovered fundamental methods of chemistry, like calcinations, distillation, sublimation, filtration and fermentation.

Major achievements of Jabir Ibne-Haiyan

1.   He was considered as first experimental or practical chemist. He is known as the Father of chemistry.
2.   He invented chemical methods like sublimation, fractional distillation.
3.   He invented experimental methods for the preparation of nitric acid, hydrochloric acid and white lead.
4.   He developed methods for extraction of metals and dyeing of clothes

Major Achievements of Al-Razi (864-930 AD)

1. He was a physician, alchemist and a philosopher.
2. He prepared alcohol (C2H5OH) by fermentation of sugar and starch.
3. He divided the substances into living and non-living origin.
4. He was an expert surgeon and was the first to use opium as anaesthesia.

Major Achievements of Al-Beruni (973-1048 AD)

1. He determined densities of different substances.
2. He contributed in physics, mathematics, geography and history.

The Modern Period
The modern chemistry began in 17th and 18th centuries. The beginning of 19th century is marked by Dalton’s atomic theory and since then, the advancement of chemistry became very rapid. The 20th century is characterized by outstanding achievements in determining structure of atoms and molecules, understanding of biochemical basis of life, the development of chemical technology and the mass production of chemicals and industrial products.

Scientists of Modern Period

Following are the contributions made by different scientists. 

1. Robert Boyle ................Was regarded as the father of modern chemistry.
2. J. Black   ......................Made a study of carbon dioxide.
3.J. Priestly.....................Discovered oxygen, hydrogen chloride and sulphur dioxide.
4.Scheele........................Discovered chlorine.
5.Cavendish ...................Discovered hydrogen.
6.Lavoisier..........................Discovered that oxygen constituted about 1/5th of air.
7.John Dalton  ............Put forward atomic theory of matter and the concept of atomic weight.
8.Gay-Lussac............Found out relative atomic and molecular masses of many substances.
9.Avogadro...............Found out relative atomic and molecular masses of many substances.
10.J.J. Berzelius ........Introduced the idea of symbols, formulae and chemical equations
11.Mendeleev............Published the periodic table of the elements.
12.Arrehenius  ...................Put forward his ionic theory of ionization.
13.M. Faraday.......Discovered the laws of electrolysis.
14.J.J. Thomson.....Discovered electrons
15.Henry Becquerel........Discovered Radioactivity
16.Madam Currie.......Established radioactivity.
17.Ken Rutherford....Discovered nucleus and put forward atomic model.
18.Neil Bohr...............Improved Rutherford’ atomic model
19.Henry Moseley............Discovered atomic number that led to the development of modern periodic table.
20. Henry Moseley............Put forward theory of unification.


Scientific Approach in Chemistry

Definition of scientific method
The scientific method is the systematic and cyclic process by which scientists, collectively and over time; endeavor to construct an accurate (that is, reliable, consistent and non-arbitrary) representation of the world. Thus a method of investigation involving observation and theory to test scientific hypotheses is called a scientific method. A scientific method or process is considered fundamental to the scientific investigation and acquisition of new knowledge based upon physical evidence.

Science is not only an integrated knowledge of physical or biological phenomenon but also the methodology through which this knowledge is collected. In science the facts are gathered through observations and experimentations and then theories or laws are deduced.

Steps of Scientific Method

[The scientific method is a cyclic process which involves observation of a phenomenon to collect facts thereby making hypothesis for prediction about that phenomenon then experimentations are carried out for testing the prediction thereby establishing a theory which if proved true then acquire the shape of law].

The scientific method includes following steps:

 

                                                                                                             
1.   Observations
Observation is basically the watching something and taking note of anything it does. In other words observation is the process of watching, noticing and recording of a natural phenomenon.  We make observations of natural processes and collect data about them. The observations are made by the five senses of man. Observation is a basic tool to go forth for elaborating a phenomenon but it may vary from person to person according to his own skill of elaboration.

2.   Hypothesis:

This is an educated guess based upon observations. It is a rational explanation of a single event or phenomenon based upon what is observed, but which has not been proved. Most hypotheses can be supported or refuted by experimentation or continued observation.  A hypothesis is an educated guess consisting of a general assumption or a proposed explanation that results from research and prior observations of a natural phenomenon or an observable phenomenon. However, a hypothesis has not been tested. It generally relates to one specific idea or phenomenon. A hypothesis is a provisional or working explanation, assumed true only to guide experimentation or for the sake of argument.                

In scientific method, the facts collected through observations are carefully arranged and properly classified correlating the knowledge thus acquired with the previous knowledge. Then scientist tries to think of a tentative solution to explain the observed phenomenon. This tentative explanation is called a hypothesis.


1.    Prediction
      It is the third step of scientific method. The inference based on observed facts is called prediction. It  gives the detailed explanation about the phenomenon on the basis of gathered facts and collected by observation and hypothesis.

2.    Experiment
The experiment is a cornerstone in empirical approach to knowledge. An experiment is an integrated activity performed under suitable conditions with specially designed measuring and observatory instruments to verify (or falsify) or to test the validity of a hypothesis. Stated differently, an experiment is a process that helps in testing the facts collected by observation, hypothesis and predictions. [The verification of hypothesis by experiment helps to improve the reliability of known facts. Even unauthentication of hypothesis by experiment still gives valuable information that can be used to deduce other results].

3.    Theory
[A hypothesis is an educated guess that results from research and prior observations of a natural phenomenon. However, a hypothesis has not been tested. When consistency is obtained through repeated experimentation, the hypothesis becomes a theory and provides a coherent set of propositions, which explain a class of phenomena.]. A theory is a well established explanation or a scientifically acceptable idea or principle to account for a phenomenon. In other words the hypothesis that is supported by repeated experimentations and proved to be true is called a theory. A theory is then a framework within which observations are explained and predictions are made. Thus a theory is a thoroughly tested model that explains why experiments give certain results. [The main difference between theory and a law is that a theory is an explanation for the pattern in the data or phenomenon and explains how it happens, often by using an analogy or metaphor while a law is just a description of a pattern in the data and merely shows what happens, without any explanation].

4.    Scientific Law

     A theory that repeatedly gives the same results after experimentation offering correct explanation of scientific facts and from which valid predictions can be made is known as Scientific Law or Scientific Principle. Thus a law is a theory that has passed the test of time and is generally accepted as truth. A Scientific Law is an accepted scientific principle taken to be correct and universally applicable. However, not all hypotheses and theories pass successfully to become scientific laws. Some hypothesis or theories may sound very convincing and are well supported by mathematical calculations but are very difficult to prove experimentally. This is invariably due to the material under consideration or the lack of the suitable working equipments. A typical example is of Avogadro’s law (or hypothesis) that has not been proved conclusively and yet it is accepted as Law.

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