WHAT IS CHEMISTRY DEFINITION AND ITS IMPORTANCE

Chapter # 01 Chemistry - IX, Night, 9th

Theory & Question Answers

INTRODUCTION TO CHEMISTRY

1.1 WHAT IS CHEMISTRY (DEFINITION AND ITS IMPORTANCE)

Q.1: Define chemistry and describe its importance.

Ans: CHEMISTRY:

Chemistry is the branch of science that deals with the proper composition and structure of

matter.

Chemistry ¡s the branch of science that deals with the study of properties, composition

and structure of matter along with chemical changes involved in it and principles

governing these changes.

IMPORTANCE OF CHEMISTRY:

Ø Chemistry enables us to design all sorts of materials like.

Ø Drugs to fight a disease.

Ø Pesticides to protect our health and crops.

Ø Fertilizers to grow our crops for abundant food.

Ø Fuels for transportation

Ø Fibers to provide comfort

Ø Variety in clothes and lot of other things.

Ø Chemistry also helps us to understand the nature of our environment and about

ourselves.

Ø The theories of chemistry help us to understand the material world from tiny atom to

giant galaxies.

1.2 LANDMARKS IN THE HISTORY OF CHEMISTRY

Q.2: Describe the historical development of chemistry. Chemistry - class Night,

Ans: HISTORICAL DEVELOPMENT OF CHEMISTRY:

Historical development of chemistry consists of following three periods.

Ø The Greek period

Ø The Muslim period

Ø The Modern Period

The Creek Period

I. GREEK PHILOSOPHERS

Greek Philosophers like Plato (347 — 428 BC), Aristotle (322 — 384 BC), Democritus

(357—460 BC) contributed a lot to the early development of chemistry.

Concept:

They introduced the concept of elements, atoms

and the chemical reactions. They thought that all

matter was derived from four elements.

Ø Earth: Earth was dry and cold.

Ø Fire: Fire was hot and dry.

Ø Air: Air was cold, wet and hot.

Ø Water: Water was cold, hot and wet.

II. ROMANS

Ø They developed the chemical arts.

Ø They improved metallurgical processes and introduced the enameling of pottery.

Ø They developed little theoretical knowing ?I this regard and their works were

all empirical (experimental).

2. THEMUSLTM PERIOD

The Muslim period was from 600 tõ1bOÀD in the history of chemistry and is known as the

period of “Alchemist”. In the field of chemistry Muslim made rich contribution and introduced

scientific methods and experimentations.

DISCOVERY OF LABORATORY EQUIPMENTS:

The Alchemists developed and used many laboratory equipment’s such as.

Ø Funnels -4

Ø Beakers I

Ø Crucibles for melting and fusion.

Ø Retorts for distillation

Ø Balances for weigh in

DISCOVERY OF CHEMICALS:

They discovered

Ø Various acids

Ø Alcohols

Ø Medicines Chapter # 01 Chemistry - 9th

CONTRIBUTION OF MUSLIM SCIENTISTS

I.JABIR BIN HAYAN (721-803 AD):

He was generally known as the father of alchemy. He was a practical chemist and built the

first ever, chemical laboratory.

Work:

Ø He invented experimental methods for the preparation

aqua regain and white lead.

Ø He also developed methods for the extraction of metals from their

Ø He invented the methods for dying of clothes.

Ø He developed the method for preparing steel and varnish.

Ø He developed the process of golden script writing with iron pry’

II. AL-RAZI (862-930 AD)

He was a physician, alchemist, a Philosopher and an expert surgeon.

Work:

Ø He divided the substances into living and non-living origins.

Ø He was first to use opium as an aesthesia.

Ø He prepared ethyl alcohol by the fermentation's j,rocess.

Ø He determined the specific gravities of different things.

Ø He classified compounds into., four goupsnÌ.e. minerals, botanical, zoological and the

derived ones.

III. AL-BERUNI (973-1048 AD)

He contributed a lot in physician metaphysics mathematics, geography and history.

Work:

Ø He worked an eighteen precious stones and metals.

Ø He determined the densities of different substances.

IV. IBNE-SINA (980-1037 AD)

He was famous for his contribution in the different fields.

Work:

Ø He contributed in medicines, medicinal chemistry, philosophy, mathematics and

astronomy.

Ø He studied the properties of minerals.

3. MODERN PERIOD

I. ROBERT BOYLE(1627 -1691 AD):

He ¡s considered as a father of modern chemistry.

Contribution:

Ø He was the first to put forward the idea that chemistry should be regarded as a

systematic investigation of nature with the sole aim f promoting knowledge

Ø His definition of elements is quite near to the modem definition.

Ø He was the first chemist to isolate and collect a gas.

Ø He formulated a gas law which is known as Boil's law.

Ø He showed that air is absorbed in the process of combustion and that only one part of

air, oxygen, is necessary for breathing.

II. J-BLACK(1728 - 1799 AD):

Contribution:

He made a study of carbon dioxide.

III. J. PRI ESLLY( 1733 - 1804 AD):

Contribution:

Ø He discovered oxygen, Sulphur dioxide and hydrogen chloride.

Iv. SCHEELE(1742 - 1786 AD):

Contribution:

Ø He discovered chlorine.

v. CAVENDISH(1731 -1810 AD):

Contribution:

Ø He discovered hydrogen

vi. LAVOISIER(1734 -1799 AD):

Contribution:

Ø He discovered that oxygen constituted about one fifth of air.

Ø He improved the chemical balance.

vii. JOHN DALTON(1766 -1844 AD):

Contribution:

Ø He proposed his atomic theory of mater.

Ø He also gave the concept of atomic weight.

viii. GAY LUSSAC(1778 - 1850 AD), DULANG(1785 - 1838 AD) & PETIT(1741 - 1020

AD):

Contribution:

Ø They led to determination of relative atomic and molecular masses of many

substances.

ix. BERZELIUS(1779 - 1840 AD):

Contribution:

Ø He devised the chemical symbols of elements, formula and chemical equation.

Ø He determined atomic masses of many elements.

X. MENDELEEV( 1824 - 1907 AD):

Contribution:

Ø He arranged all the known elements periodically hi a table known as Mendeleev’s

table.

Ø Mendeleev’s table helps in the study of properties of elements and discovery of new

elements.

xi. ARRHENIUS (1859- 1927 AD)::

Contribution:

Ø He put forward the ¡one theory.

Role of chlorine for killing pathogenic organisms:

Diseases like cholera, typhoid and dysentery are transmitted through impure drinking

water. Water is treated with chlorine to kill pathogenic (disease causing) organisms of

these diseases.

.- Role of chemistry in industries:

Chemistry plays an important role in the modem world. For example the major gifts of

chemistry are synthetic fibers, plastics, soap, detergent, cosmetics, cement, fertilizers,

glass and explosives

‘ Role of chemistry In environment:

Environmental chemistry tells us that how One can protect its environment from

environmental hazards. It helps in providing everyday needs of food, clothing and

shelters.

r Role of chemistry In medicines:

i. Modern surgery is dependent on chemical such as anesthetics and antiseptics.

ii. Using chemistry we have discovered pharmaceutical chemicals that enhance our

health and prolong our lives.

xii. FARADAY( 1791 - 1867 AD):

Contribution:

Ø He examined the effect of electricity on solutions.

Ø He also presented the laws of electrolysis.

xiii. HENERY BECQUERAI:

Contribution:

Ø He discovered radioactivity and discovered Polonium and Radium.

xiv. J.J.THOMSON:

Contribution:

Ø He discovered negatively charged particle electron.

Ø He discovered alpha and Beta rays.

xv. RUTHERFORD:

Contribution:

Ø He discovered nucleus. He gave model of atomic structure.

xvi. NEIL’S BOHR:

Contribution:

Ø He gave structure of atomic model and removed defects in Ruther Ford’

model.

1.3 CHEMISTRYANDSOCIETY

Q.3: What are the significant reasons to study chemistry?

Ans: SIGNIFICANT REASONS:

There are three significant reasons to study chemistry.

Ø Practical Applications:

Chemistry ¡s studied because it has important practical applications ¡n the so

example

i. Development of life saving drugs.

ii. Modem Technology

Ø intellectual enterprise:

Chemistry is an intellectual enterprise, a way of explaining our material world.

Ø intellectual tool:

Chemistry in every field is a useful Intellectual tool for making important decisions. It

figures prominently in other fields, such as in biology in the advancement of medicines

Q.4: What important role chemistry plays in the society?

Ans: ROLE OF CHEMSTRY IN THE Society:

The role of chemistry in the prevailing society is of enormous benefits.

Ø Role of chlorine for making plastics:

Chlorine is used in chemical industries for producing poly Vinyl Chloride (PVC) as

plastics for pipes.

Ø Role of chlorine compounds:

Chlorine compounds are used as bleaching agent, disinfectants, solvents, pesticides,

ref rig rants, flame retardant and drugs.

Ø Role of chlorine for killing pathogenic organisms:

Diseases like cholera, typhoid and dysentery are transmitted through impure drinking

water. Water is treated with chlorine to kill pathogenic (disease causing) organisms of

these diseases.

Ø Role of chemistry in industries:

Chemistry plays an important role in the modem world. For example the major gifts of

chemistry are synthetic fibers, plastics, soap, detergent, cosmetics, cement, fertilizers,

glass and explosives.

Ø Role of chemistry In environment:

Environmental chemistry tells us that how One can protect its environment from

environmental hazards. It helps in providing everyday needs of food, clothing and

shelters.

Ø Role of chemistry In medicines:

i. Modern surgery is dependent on chemical such as anesthetics and antiseptics.

ii. Using chemistry we have discovered pharmaceutical chemicals that enhance our

health and prolong our lives.

1.4. BRANCHES OF CHEMISTRY

Q.5: Name the different branches of chemistry and define them.

Ans: BRANCHES OF CHEMISTRY:

The main branches of chemistry are:

i. Physical Chemistry

ii. Organic Chemistry

iii. Inorganic Chemistry

iv. Analytical Chemistry

v. Bio Chemistry

vi. Industrial and Applied Chemistry

vii. Nuclear Chemistry

viii. Environmental Chemistry

ix. Polymeric Chemistry

I. PHYSICAL CHEMISTRY:

Definition:

It is the branch of chemistry that deals with the laws and the principles governing

the combination of atoms and molecules on chemical reactions.

ii ORGANIC CHEMISTRY:

Definition:

It is the branch of chemistry that deals with carbon compounds with the exception

of CO2, CO, metal carbonates, bicarbonates and carbides. Actually it is the chemistry

of hydrocarbons and their derivatives. Most of the consumers products are organic

in nature.

III. INORGANIC CHEMISTRY:

Definition:

It is the branch of chemistry that deals with the chemistry of elements and their

compounds, generally obtained from non-living organisms i.e. from minerals.

iv. ANALYTICAL CHEMISTRY:

Definition:

It is the branch of chemistry that deals with the study of the methods and

techniques involved to determine the kind, quality and quantity of various

components in a given substance.

V. BIOCHEMISTRY:

Definition:

It is the branch of chemistry that deals with the compounds of living organisms i.e.

plants and animals and their metabolism in the living body.

VI. INDUSTRIAL Chemistry:

Definition:

It is the branch of chemistry that deals with the study of different chemical

processes involved in the chemical industries for the manufacture of synthetic

products like glass, cement, paper soda ash, fertilizers medicines etc.

vii. NUCLEAR CHEMISTRY:

Definition:

It is the branch of chemistry that deals with the study of changes occurring in the

nuclei of atoms, accompanied by the emission of invisible radiations.

Viii. ENVIRONMENTAL CHEMISTRY:

Definition:

It is the branch of chemistry that deals with the study of the interactions of chemical

materials and their effect on the environment of animals and plants. Personal

hygiene, pollution and health hazards are important areas of environmental

chemistry.

IX. POLYMERIC CHEMISTRY:

Definition:

It is the branch of chemistry that deals specially with the study of polymerization

and the products obtained through the process of polymerization such as plastics,

synthetic fibers, papers etc.

Q.6: Describe importance of different branches of chemistry in human life?

Ans: IMPORTANCE OF CHEMISTRY IN MODERN WORLD:

Chemistry plays an important role in the modem world in the following ways.

Biochemistry:

Ø It is the backbone of medical science.

Ø Modern surgery is dependent on chemicals such as anesthetics and antiseptics.

Ø It has improved the standard of living by improving health conditions.

Analytical Chemistry:

Ø Analytical chemistry is important to understand the composition of compounds, quality

of products and analysis of biological samples.

Industrial Chemistry:

Ø Chemistry has made efforts for better utilization of the natural resources.

Ø Industrial chemistry helps us in manufacturing of industrial products e.g. food, fiber,

plastic, medicine, detergents, paints etc.

Environmental Chemistry:

Ø Environmental chemistry tells us that how one can protect its environment from

environmental hazards.

Nuclear Chemistry:

Ø Many explosives, poisonous gases and other chemical weapons used in chemical war

are the products of chemistry.

Ø Nuclear chemistry provides us radioisotopes for the treatment of many diseases such

as cancer.

1.5 SCIENTIFIC APPROACH IN CHEMISTRY

(OBSERVATION, HYPOTHESIS, THEORY ARID Law)

Q.7: What is the scientific method? What are the various steps of scientific method?

Ans: SCIENTIFIC METHOD:

Definition:

The method, which helps to collect facts on the basis of

observations and experiments is called scientific method.

Theories and law are then formulated to explain these

facts.

STEPS OF Scientific METHOD

The scientific method includes the following four steps.

i. observation

ii. Hypothesis

iii. Theory

iv. Scientific Law

I. OBSERVATION

Definition:

The process of observing natural phenomenon with the help of five senses and the

scientific equipment’s ¡s called observation. The information acquired through

careful observation is called fact.

Explanation:

Observation is a basic tool to go forth elaborating a phenomenon but it may vary

from person to person according to his own skill of elaboration. Observation of a

thing is one of the scientific approaches in chemistry.

Means Of Observation:

i. Five senses of man

ii. Equipments

Microscope: Used for observing minute object.

Thermometer: Used for accurate measurement of temperature.

Sensitive Chemical Balance: Used for finding the mass of very light objects.

Measuring Apparatus: e.g. Relative Density bottle, measuring cylinder,

measuring flask etc.

II. HYPOTHESIS:

Definition:

The explanation of observations and facts is called hypothesis.

Explanation:

When a phenomenon is observed; a scientist ponders over it and cranes out

relevant experiments. He sieves through the data and arrives at a possible

explanation for the nature of the phenomenon. This explanation; which is still only a

trial idea is called hypothesis. It may or may not undergo a charges a result

further investigations and accumulation of more knowledge or facts.

III. THEORY:

Definition:

If a hypothesis is accepted it ¡s called theory.

Explanation:

The Scientist conveys his hypothesis to other workers of the same field for the

discussion and for further experimentation. When the hypothesis is supported by a

large amount of different types of observations and experiments, then it becomes a

theory i.e. scientifically acceptable idea or principle to explain a phenomenon.

A good theory predicts new facts and unravels new relationship between naturally

occurring phenomenon.

Examples:

Dalton’s atomic theory, Bohr’s theory of atomic structure etc.

IV. SCIENTIFIC LAW:
Definition:

A theory which is tested again and again and found to fit the facts and from which

valid Predictions may be made is then known as scientific law or principle.

Examples:

Law of conservation of mass, Faraday’s law of electrolysis etc.

V. CONCLUSION:

Not all hypothesis and theories pass successfully to become scientific laws. Some

may found very convincing and be supported by mathematical calculations but are

very difficult to prove experimentally. This is invariably due to the material under

investigation or the lack of suitable working equipments. A typical example is

Avogadro’s hypothesis which has not been proved conclusively and yet it ¡s

accepted as Avogadro’s law.