Q. What is chemistry? What are various branches of chemistry? Chemistry

Q. What is chemistry? What are various branches of chemistry? Ans. Chemistry:

Chemistry is defined as the science that examines the materials of the universe and changes that these materials undergo

Or

The branch of science which deals with the composition, structure, properties and reaction of matter is called Chemistry.

Branches: There are eight branches of chemistry.

i. Physical Chemistry: The branch of chemistry that deals with laws and theories to understand the

structure and changes of matter is called physical chemistry.

ii. Organic chemistry:

The branch of chemistry that deals with substances containing carbon is called organic chemistry.

Some carbon compound such as CO2, CO, metal carbonates, hydrogen carbonates and carbides are studied in inorganic chemistry.

iii. Inorganic Chemistry: The branch of Chemistry that deals with elements and their compounds except organic compounds is called Inorganic Chemistry.

iv. Biochemistry:

The branch of Chemistry that deals with physical and chemical changes that occur in living organisms is called Biochemistry.

v. Industrial Chemistry: The branch of Chemistry that deals with the methods and use of technology in the large scale production of useful substances is called Industrial chemistry.

vi. Nuclear Chemistry: The branch of Chemistry that deals with the changes that occur in atomic nuclei is called Nuclear Chemistry.

vii.Environmental Chemistry: The branch of Chemistry that deals with the chemical and toxic substances that pollute the environment and their adverse effects on human beings is called environmental chemistry.

viii. Analytical Chemistry:

The branch of Chemistry that deals with the methods and instruments for determining the composition of matter is called Analytical Chemistry.

Q. Vinegar contains 5% acid. Acetic and (CH3COOH) is a colourless liquid that has characteristic vinegar like smell. It is used to flavour food. Identify the various branches of chemistry.

i. Methods of preparation and study of chemical characteristics of acetic acid. Ans. Organic Chemistry ii. The study of chemical reactions that acetic acid undergoes in the bodies of human

beings. Ans. Bio Chemistry iii. The study of its component elements carbon, hydrogen and oxygen. Ans. Inorganic Chemistry iv. Use of technology and ways to obtain acetic acid on the large scale. Ans. Industrial Chemistry v. Explanation of its transformation into gaseous state or solid state, applications of

laws and theories to understand its structure. Ans. Physical Chemistry vi. The method and instruments used to determine its percentage composition,

melting point, boiling point etc. Ans. Analytical Chemistry vii. The study of any adverse effects of this compound or the compounds that are

derived from it, on the human. Ans. Environmental Chemistry viii. The study of the effect of radioactive radiations or neutron on this

compound or its component elements. Ans. Nuclear Chemistry

Example 1.1 Identify the branch of chemistry in each of the following cases.

i. Photosynthesis produces glucose and oxygen from carbon dioxide and water in presence of chlorophyll and sunlight.

ii. Plantation helps in overcoming greenhouse effect.

iii. Haber's process converts large quantities of hydrogen and nitrogen into ammonia (NH3)

iv. Ammonia is colourless gas which present irritating odour. It is highly soluble in water.

v. A chemist performed an experiment to check the percentage purity of a sample of glucose (C6H12O6).

vi. An analyst determines that NO2 is responsible for acid rain. vii. Chlorofluorocarbon compounds are responsible for the depletion of ozone

layer. viii. -particles (He++) when bombard on nitrogen atom, a proton is emitted. Solution: i. Biochemistry, since photosynthesis is a chemical reaction that occur in

plants (living organisms). ii. Environmental chemistry, since greenhouse effect is an environmental

problem. iii. Industrial chemistry, since large scale production of any substance is the

subject of industrial chemistry. iv. Inorganic chemistry, since it deals with properties of inorganic compounds. v. Analytical chemistry, since it deals with analysis of a compound, whether

organic or inorganic in nature. vi. Environmental chemistry since acid rain is an environmental problem vii. Environmental chemistry, since depletion of ozone layer is environmental

problem viii. Nuclear chemistry, since nuclear change can emit protons.

Identify the branch of chemistry that is related to the following information: i. Hair contains a special class of proteins called keratins, which are present in

nails and wool. Ans. Bio-Chemistry ii. Acetylene is the simplest hydrocarbon that contains carbon-carbon triple bond.

Hydrocarbons are the compounds of carbon and hydrogen

Ans. Organic Chemistry iii. While lead is a pigment used by artists for centuries, the metal Pb is the

compound is extracted from its ore, galena (PbS). Ans. Industrial Chemistry iv. Sulphuric and (H2SO4) is weaker than hydrochloric acid Ans. Analytical Chemistry v. Gases can be compressed by applying pressure. Ans. Physical Chemistry vi. Some examples of complete proteins food are meat, milk and eggs. Ans. Bio-Chemistry vii. Element radium decays by emitting -particles and is converted into another

element radon. Ans. Nuclear Chemistry viii. Calorimeter is a device that measures the amount of heat, a substance absorbs

on heating or emits on cooling. Ans. Analytical Chemistry

Q. Give postulates of Dalton's atomic theory? Ans. Dalton's Atomic Theory:

Main postulates of Dalton atomic theory are as follows: i. All elements are composed of tiny individuals particles called atoms. ii. Atoms of a particular element are identical. They have same mass and same

volume. iii. During chemical reaction atoms combine or separate or re-arrange. They

combine in simple ratios. iv. Atoms can neither be created nor destroyed.

Q Define following: (i) Element:

A substance that cannot be converted to other simpler substance is called an element. (ii) Compound:

A compound is a pure substance that consists of two or more elements held together in fixed proportions by natural forces called chemical bonds. Compounds have sharp melting point.

(iii) Mixture:

An impure substance that contains two or more pure substances that retain their individual chemical properties is called a mixture. Mixtures do not have sharp melting point.

(iv) Atomic Number: The number of protons in the nucleus of an atom is known as its atomic number.

(v) Mass Number: The total number of protons and neutrons in an atom is known as its mass number

Example 1.2 Atomic number of an element is 17 and mass number is 35. How many protons and neutrons are in the nucleus of an atom of this element? Solution: Number of protons = atomic number = 17 Number of neutrons = mass number - atomic number = 35 ? 17 = 18

Write the empirical formulas for the compound containing carbon to hydrogen

in the following ratios

(a) 1 : 4

CH4

(b) 2 : 6

CH3

(c) 2 : 2

CH

(d) 6 : 6

CH

1. Aspirin is used as a mild pain killer. There are nine carbon atoms, eight hydrogen atoms and four oxygen atoms, in this compound. Write its empirical and molecular formulas.

Ans. Molecular formula of Aspirin is C9H8O4 Empirical formula of Aspirin is C9H8O4

2. Vinegar is 5% acetic acid. This contains 2 carbon atoms, four hydrogen atoms and 2 oxygen atoms. Write its empirical and molecular formulas.

Ans. Molecular formula of Vinegar is C2H4O2 Empirical formula of Vinegar is CH2O

3. Caffeine (C8H10N4O2) is found in tea and coffee. Write the empirical formula for caffeine.

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