Notes of Chapter # 01 [Introduction to Chemistry]

UNIT# 01

INTRODUCTION TO CHEMISTRY

Chemistry has a magnificent role and enormous benefits. Many of the chemicals are being used in our daily lives for various purposes. Chemistry is an extremely practical science and has deep influence on our lives. Unfortunately, some chemicals have the potentials of harming our health and/or the environment. It is in our best interest as educated citizens, both positives and negatives that chemicals have on our health.

Define the following terms.

●      Matter

●      Atom

●      Molecule

●      Substance

●      Element

●      Symbol

●      Valency

●      Chemical formula

●      Compound

●      Mixture

MATTER

Anything that takes up space and has mass is called matter.

STATES OF MATTER

Following are the three states of matter:

1.     Solid

2.     Liquid

3.     Gas

ATOM

Atom is the basic unit of matter and defines structure of elements. Atom is even is composed of three sub particles called electron (e^-), proton (p⁺) and neutron (n^o).

MOLECULE

A molecule is the smallest particle in a chemical element or Compound that has the chemical properties of that element or Compound.

Molecules are made up of atoms that are held together by chemical bonds. Molecules may be monoatomic, diatomic or polyatomic.

 

Monoatomic molecules	Diatomic molecules	Triatomic molecule	Polyatomic molecules
H	O2	H2O	NH3
He	N2	CO2	P4
Li	Cl2	SO2	S8
Ar	Br2	N2O	C6H12O6
Xe	I2	CaCl2	C2H5OH

SUBSTANCE

A piece of pure matter is called substance.

Each and every substance has same composition with specific structure with specific physical and chemical properties.

For instance:

Tin, sulphur, diamond, baking soda etc

ELEMENT

An element is a substance made up of same type atoms, having same atomic number and that cannot be decomposed further.

On the basis of their properties, elements are categorized into metals, non metals and metalloids.

For instance:

Oxygen, helium, carbon, nitrogen, sodium etc

CHEMICAL SYMBOL

Letter or group of letter which are use to denote any specific element is called chemical symbol.

For instance:

·        Symbol to represent Carbon is C

·        Symbol to represent Oxygen is O

·        Symbol to represent Helium is He

HOW TO WRITE SYMBOL

Following points should be remembered while writing symbols.

●      Symbols are usually one or two letter long.

●      Every symbol starts with capital letter as carbon with C or sulphur as S.

●      If symbol consists of two letters, the first will start with capital and second will be in small letter as He for helium, Na for sodium, Cr for chromium.

VALENCY

Valency is the number of electron of an atom in the outermost shell that can gain, lose or share. 

Valency depends upon the number of electrons in the outermost shell. Atom gain/ donates electron, on the basis of the presence of electron in its outermost shell.

 

Group I	Group II	Group III	Group IV	Group V	Group VI	Group VII	Group VIII
+1	+2	+3	+/-4	-3	.2	-1	0
Li	Be	B	C	N	O	F	Ne
Na	Mg	Al	Si	P	S	Cl	Ar

CHEMICAL FORMULA

The chemical formula represents the symbol of elements and ratios of elements to one another in a compound.

For instance:

Chemical formula of water is H₂O which indicates that 2 atoms of hydrogen combine with 1 atom of oxygen.

Chemical formula of Carbon dioxide is CO₂ which indicates that 1 atom of carbon combines with 2 atoms of oxygen.

COMPOUNDS

The Compound is a substance formed by the chemical combination of two or more elements.

The type of bonds holding elements may be ionic bonds or covalent bonds

For Example: NaCl, CuSO₄, KBr are ionic compound and H₂O, CH₄ H₂SO₄ are covalent compounds. 

MIXTURE

The physical combination of two or more than two substances without any fixed ratio is called mixture. There are two types of mixtures i.e. homogenous mixtures and heterogeneous mixtures.

●      Homogenous mixtures: In this type of mixtures, all substances are evenly distributed. For instance: salt water, blood etc.

●      Heterogeneous mixtures: In this type of mixtures, substances are not evenly distributed. For instance: pizza, rocks, cookies etc.

Mixtures can be separated by using any of the technique mentioned below:

●      Evaporation

●      Distillation

●      Filtration

●      Crystallization

Q. Differentiate between element, compound and mixtures.

 

Element	Compound	Mixtures
Element is a substance made up of same atoms.	Compound is formed by the chemical combination of atoms.	Mixture formed by the simple mixing of the substances.
Element shows unique properties.	Constituent of compound lose their identity and form a new substance with new properties.	Constituents of mixture retain their properties in mixture.
They cannot decompose into simple substances.	Component s cannot be separated by physical means.	The components can be separated by physical means.
Element represented by symbols.	Every compound represented by chemical formula.	They don’t have particular formula.
Element are homogenous	Compounds are heterogeneous	Mixtures may be homogenous or heterogeneous.
Greater the atomic number, greater will be melting points.	Fixed & sharp melting points.	Don’t have sharp and fixed melting points.

Define relative atomic mass.

RELATIVE ATOMIC MASS (ATOMIC MASS) AND ATOMIC MASS UNIT (amu)

The Relative atomic mass of an atom is the average mass of naturally occurring isotopes, compared carbon (C-12).

A_r = Average mass of one atom of the element

            1/12^th x mass of C-12

Its unit is atomic mass unit, with symbol a.m.u.

1 amu =1.66 x 10^-12 gram

Q. Define empirical formula.

EMPIRICAL FORMULA

The formula that shows relative numbers of each type of atoms in a molecule is called Empirical Formula.

OR

Empirical Formula shows simplest ratio of each atoms present in a molecule.

For instance:

Benzene has molecular formula C₆H₆

It shows the ratio as follows:

C₆H₆

6:6

1:1

So, empirical formula of benzene is CH

Glucose has molecular formula C₆H₁₂O₆

It shows the ratio as follows:

C₆H₁₂O₆

6:12:6

1:2:1

So, empirical formula of glucose is CH₂O

Define molecular formula.

MOLECULAR FORMULA

The Molecular formula is the formula which shows actual number of atoms of each element present in a molecule.

For Example:

Molecular Formula of benzene is C₆H₆

Molecular Formula of glucose is C₆H₁₂O₆

Define atomic number with examples.

ATOMIC NUMBER OR CHARGE NUMBER

The number of proton present in the nucleus of an atom represents the atomic number.

For example

Sodium atom has 11 electrons and 11 protons in its nucleus, thus, its atomic number is 11.

Define mass number with examples.

MASS NUMBER

The sum of number of protons and neutrons present in the nucleus of an atom is called mass number.

For instance:

·        Carbon atom has 6 protons and 6 neutrons in its nucleus so its mass number is 12.

·        Oxygen atom has 8 protons and 8 neutrons in its nucleus so its mass number is 16.

Define molecular formula mass with examples.

MOLECULAR FORMULA MASS

The sum of the atomic masses of all the atoms present in a molecular formula of a substance or molecule is called molecular formula mass.

It is expressed in amu.

For example:

Molecular formula mass of CO₂ = 12 + (16X2)

Molecular formula mass of CO₂= 44 a.m.u

 

Molecular formula mass of H₂O = 2 + (16X1)

Molecular formula mass of H₂O = 18 a.m.u.

Define Formula mass with example.

FORMULA MASS

The sum of all atoms present in a formula unit of the substance is called formula mass.

Note:

Some compounds only exist in ionic form, so we can calculate their formula mass not molecular mass.

Formula mass of NaCl  = 23 + 35.5

Formula mass of NaCl  = 58.5

Define Molar mass with example.

MOLAR MASS

Molar mass of the substance is the relative mass expressed in grams.

For example

1 molecular mass of carbon is 12 gm, thus its molar mass would be 12 gm.

 

SIMILARLY

NH₃

N = 14 X 1 = 14

H = 1 X 3 = 3

NH₃ = 14 + 3 = 17gm

 

NO₂

N = 14 X 1 = 14

O = 2 X 16 = 32

NH₃ = 14 + 32 = 46 gm 

Define ions. Also define its types.

IONS

An atom or group of atom having charge on it due to gain or lose of electron is called Ion. There are two types of ions, cations and anions.

●      Cations are formed when an atom loses electrons form its outer most shells.

For example: Na⁺, K⁺ are cations.

Na       →        Na⁺ + e^-

●      Anions are formed by the gain or addition of electrons to an atom.

For example: Cl^- and O^-2

Cl + e^-            →        Cl^-

 

MOLECULAR IONS

When a molecule loses or gains electrons, it is called molecular ions.

Molecular ions also possess positive or negative charge like any ion.

●      If it has negative charge known as anionic molecular ions, for example ClO₄^-

●      If they has positive charge known as cationic molecular ions. For example CH₄⁺

FREE RADICALS

When atom or group of atoms has number of unpaired electrons then it is called free Radicals.

For example: H^o, Cl^o, H₃C^o etc.

Differentiate between atom and ion.

 

Atom	Ion
Atom is the smallest particle of an element.	Ion is the smallest unit of ionic compound
Atom can or cannot exist independently.	Ion cannot exist independently.
Atom is electrically neutral.	Ion has negative or positive charge.

Differentiate between molecule and molecular ion.

 

Molecule	Molecular ion
Molecule is the smallest particle in a chemical element or compound.	Molecular ions formed by gain and lose of electrons.
Molecule is always neutral.	Molecular ion has positive or negative charge.
Molecule is stable unit.	Molecular ion is reactive specie.
Molecule is formed by the combination of atoms.	Molecular ion formed by the ionization of a molecule.

 Q. Differentiate between ion and free radicals.

 

Ion	Free radicals
Ions are atoms which have positive or negative charge.	Free radicals are atoms with odd number of unpaired electrons.
Ions exist in crystals and solutions.	Free radicals exist in air and solutions.
Ions are not affected by the presence of light.	Free radicals are affected by the presence of light.

 

Define Chemical equation with example.

CHEMICAL EQUATION

The representation of a chemical reaction through symbols and formula is called chemical equation.

For example

H₂+ O₂           ⟶       2H₂O

HOW TO WRITE CHEMICAL REACTION

●      Elements written before the arrow or left hand side are called reactants.

●      Elements written after the arrow or right hand side are called reactants.

●      Reactants and products are separated by single ⟶ or double ⥧ arrow.

●      The number written in front of formula is called coefficient which shows number of molecules of that reactant or product.

●      The expression (s), (g) and (l), (aq) shows the state; solid, gaseous, liquid and aqueous condition of reactants and products.

What is mean by balancing of chemical equation? Describe the rules to balance the chemical reaction.

BALANCING OF CHEMCIAL EQUATION

To study any chemical reaction, it is necessary that reaction should be balanced and follows the law of chemical combinations.

RULES TO BALANCE CHEMICAL REACTION

1.     Formula of reactant and product should be balanced

2.     Number of atoms should be balanced

3.     Find the mass of atom in chemical reaction (reactant and product)

4.     If number of atoms are greater in one side balance the atoms by the multiply the coefficient then again find the mass of atoms.

Define gram atomic mass with examples.

GRAM ATOMIC MASS

The atomic mass of an element expressed in gram is called gram atomic mass.

It is also called 1 mole.

1 gram atom of oxygen = 16.00g = 1 mole of oxygen atom

1gram atom of carbon = 12.00g = 1 mole of carbon atom

1 gram atom of nitrogen = 14.00g = 1 mole of nitrogen atom

Its means 1gram atom of different elements has different masses.

Define gram molecular mass with examples.

GRAM MOLECULAR MASS

The molecular mass of an element or a compound expressed in gram is called gram molecular mass.

It is also called 1 mole.

1 gram molecule of oxygen (O2) = 32.00g = 1 mole of oxygen molecule

1gram molecule of water (H₂0) = 18.00g = 1 mole of water

1 gram molecule of ethanol C₂H₅OH = 46.00g = 1 mole of ethanol

Define gram formula mass with examples.

GRAM FORMULA MASS

The formula mass of an ionic compound expressed in grams is called gram formula mass.

It is also called 1 mole.

1 gram formula of NaCl = 58.5g = 1 mole of sodium chloride

1gram formula mass of CaCO3 = 100g = 1 mole of calcium carbonate

Define mole with example.

MOLE

The molecular mass, atomic mass or formula mass of the element expressed in gram is known as mole.

For example

1 mole of nitrogen = 14 gm

1 mole of carbon = 12 gm

1 mole of CO₂ = 44 gm

Define Avogadro’s number with example.

AVOGADRO’S NUMBER

A mole of a substance always contains the same number of particles (atoms, ions, molecules) irrespective of its state is called Avogadro’s number.

Its value is 6.02 X 10²³ atoms.

For example:

1 mole of C = 6.02X10²³ atoms

1 mole of CO₂ = 6.02X10²³ atoms

Describe mole mass calculation.

MOLE MASS CALCULATION

Number of moles of a substance can be calculated with the help of following equation.

Number of Moles = Known mass of substance

             Molar mass of substance

Mass of a substance can be calculated by:

Mass of substance= Number of moles x Molar Mass

 

Describe mole particle calculation.

MOLE PARTICLE CALCULATION

Number of moles of a substance in given number of particles can be calculated by:

Number of moles = Given number of particles = Given number of particles

                                                Avogadro’s number                     6.02 x 10²³

It can also be written as:

Number of particles = number of moles X Avogadro’s number

 

Describe mole volume calculation.

MOLE VOLUME CALCULATION

According to Avogadro, one gram mole of any gas at STP occupies volume of 22.4 dm³ (when standard temperature is 0⁰C and standard pressure is 1 atm)

 

Describe the significance of Chemistry in our daily life.

SIGNIFICANCE OF CHEMISTRY

Chemistry has a vital role in the development of living organisms, its variation and researches are increasing day by day. It can never be a hypothesis that chemistry has made the life free from problems by introducing the chemical reagents which are necessary for the life and also for the competition like wars.

1.     Cooking, eating and digestion of food are purely chemical processes.

2.     It has a vital role in the in the development of life saving drugs.

3.     It matters with the protection of environment, providing everyday needs of food, clothing and shelters.

4.     Pharmaceutical chemistry has enhanced our health and prolongs our lives.

5.     It enables us to design pesticides, insecticides to protect our crops and also fertilizers to increase the productivity.

 

Define chemistry and its branches.

CHEMISTRY AND ITS BRANCHES

Chemistry is the branch of science that deals with the properties, composition and structure of matter. It also deals with the changes in matter.

It has following main branches:

●      Organic chemistry

●      Inorganic chemistry

●      Polymeric chemistry

●      Physical chemistry

●      Bio chemistry

●      Environmental chemistry

●      Analytical chemistry

●      Nuclear chemistry

●      Industrial/ applied chemistry

●      Quantum chemistry

●      Green chemistry

ORGANIC CHEMISTRY

The branch of chemistry that deals with the hydrocarbon except carbonates, bi-carbonates and their derivatives is called organic chemistry. It is in fact considered as the back bone of Chemistry.

INORGANIC CHEMISTRY

The branch of chemistry that deals with chemistry of elements and their compounds that is generally obtained from minerals is called Inorganic chemistry. 

POLYMERIC CHEMISTRY

It deals with the process of polymerization and the products obtained through the process of polymerization such as plastics, synthetic fibers etc.

PHYSICAL CHEMISTRY

It deals with the laws and the principles governing the combination of atoms and molecules.

BIO CHEMISTRY

It deals with the study of living organisms and the process of metabolic activities. 

ANALYTICAL CHEMISTRY

It is the branch of chemistry that deals with the study of methods and techniques involved to determine the kind, quality and quantity of various compounds or substances.

NUCLEAR CHEMISTRY

It deals with the changes occurring in the nuclei of an atoms accompanied by the emission of radiations.

ENVIRONMENTAL CHEMISTRY

It tells about environmental composition and the protection from the environment.

APPLIED/ INDUSTRIAL CHEMISTRY

It deals with the study of different chemical processes involved in chemical industries for preparation and manufacture of synthetic fibers such as cement, glass, fertilizers, medicines etc.

QUANTUM CHEMISTRY [MOLECULAR QUANTUM MECHANICS]

The branch of Chemistry that deals with the application, mechanics and experiments of physical models in chemical system is called quantum chemistry OR Molecular quantum chemistry.

MEDICINAL CHEMISTRY

It deals with the study of synthesis and production of drugs and their mode of action on living body.

GREEN CHEMISTRY [SUSTAINABLE CHEMISTRY]

It is the branch of chemistry which deals with study of processes and designing products, which are composed of less hazardous substances.

 

Describe the role of scientists in the development of Chemistry.

ROLE OF SCIENTISTS IN THE EARLY DEVELOPMENT OF CHEMISTRY

A number of scientists played vital role in the progress of Chemistry. They part their role via using different researches, techniques and described many different and un-discovered processes. Role of few scientists are describing below:

 

SCIENTISTS	CONTRIBUTION
JABIR IBN-E-HAYAN	He is usually known as the father of chemistry. He introduced the experimental method for the preparation of nitric acids, hydrochloric acid, white lead etc. He also developed the methods for the extraction of metals from their ores and dyeing clothes.
AL RAZI	He was a great known surgeon. He was the first researcher who used opium as the anesthesia. He classified the substances into living and non-living origins. He also prepared alcohol by the process of fermentation.
AL BERUNI	He introduced the methods of determination of densities of different substances.
IBN E SINA	Contributed in medicines, philosophy and astronomy.
ARISTOTLE	Hs described the theory of four elements i.e. earth, air, fire and water.
PLATO	He proposed the term ‘element’ as composition of organic and inorganic bodies with particular structure.
DEMOCRITUS	Proposed the idea of atom, an indivisible particle of matter
ROBERT BOYLE	He proposed that chemistry should be regarded as the systematic investigation of nature with the sole aim of promoting knowledge.
J. BLACK	He made a brief study of carbon
JOSEPH PRIESTLEY	He discovered many unknown chemicals like oxygen, sulphur dioxide and hydrogen chloride.
SCHEELE	He measured the amount of the air suitable for combustion and found it to be about one fourth of the ordinary air.
CAVENDISH	He made Hydrogen by dissolving metals in acids. By dissolving alkalis in acids, he made ‘fixed air’ (carbon dioxide)
LAVOISIER	He is most noted for his discovery of the role of Oxygen plays in combustion. He recognized and named oxygen. He is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen (1778) and hydrogen (1783), and opposed the phlogiston theory. Lavoisier helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature.
JOHN DALTON	He proposed the Atomic Theory in 1803 which stated that all matter is composed of small particles called atoms.
GAY LUSSAC	He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen.
AMEDEO AVOGADRO	His principal contribution to chemistry was a paper in which he advanced two hypotheses: (1) that equal volumes of gas contain equal numbers of molecules and (2) that elementary gases such as hydrogen, nitrogen, and oxygen were composed of two atoms.
JACQUES CHARLES	Described the gaseous laws.
PETIT AND DULANG	Dulang and Petit found that the heat capacity of a mole of many solid elements is about 3R, where R is the modern constant called the universal gas constant.
BERZELLIUS	Berzelius was best known for his determination of atomic weights, chemical notation, isolation and discovery of silicon, selenium, thorium and cerium periodic table elements. He is known as "The Father of Swedish Chemistry".
MENDELEEV	He is considered to be the most important contributor to the development of the periodic table. His version of the periodic table organized elements into rows according to their atomic mass and into columns based on chemical and physical properties
ARHENIUS	He made important contributions to chemical kinetics and many other branches of science.
FARADAY	His discoveries include the principles underlying electromagnetic induction, diamagnetism and electrolysis
JOSEPH JOHN. THOMSOSN	Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged.
RUTHERFORD	Rutherford postulated the nuclear structure of the atom, discovered alpha and beta rays, and proposed the laws of radioactive decay. He received the Nobel Prize in Chemistry in 1908.
SCHRODINGER	Proposed Quantum mechanical model of atom.
DE BROGLIE	Proposed hypothesis about wave particle duality nature of electron.
STENDRA NATH BOSE	Proposed fourth state of matter.
ELBERT EIENSTEIN	Proposed fourth state of matter.
ERIC CORNELL	Synthesized the first Bose Einstein Condensate.
CARL WEIMAN	Produced first bose Einstein Condensate
NEIL BOHR	Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element.

Many of the scientists also played a vital role in the development of Chemistry. They also enhanced the chemistry by promoting many different ideas; their ideas should be regarded as the early revolutionary ideas.