Chemistry, a branch of physical science, is the study of the composition, properties and behavior of matter.

Father of modern chemistry :- Antoine Lavoisier was a French nobleman and chemist central to the 18thcentury chemical revolution and a large influence on both the history of chemistry and the history of biology. He is widely considered in popular literature as the “father of modern chemistry”

In general it exists in 3 states i.e.,
(i) Solid
(ii) liquid
(iii) gas.

Study for civil services :-
Now-a-days there is a discussion on two more states of matter
i.e., Plasma {Ionised gases containing super energetic and super excited particles }

and Bose-Einstein condensates or BEC (a gas at super low temperatures with extremely low density).

Boiling Point  The temperature at which liquid converts in to vapours is called its boiling point.  Boiling point of water is 100°C.  The boiling point increases in the presence of impurities.  That’s why boiling point of sea water is more than the boiling point of pure water (as the former contains impurity).

Study for civil services :-
 It usually decreases at high altitudes, that’s why at high altitudes, the boiling point of water is less than 100°C and more time is required to cook a food.

Melting Point

 It is a temperature at which a substance converts from its solid state to liquid state.  Melting point of ice is 0°C; It decrease in the presence of impurity

Atom, Molecule and Element

 Atom is the smallest particle of a matter that takes part in chemical reactions, but cannot exist in free state.

 Atom is made of electrons, protons and neutrons.

Study for civil services :-
 Protons and neutrons reside in the nucleus (at the centre of atom)

whereas electrons revolve around the nucleus.

 Atoms combine to form molecules, the smallest part of matter which can exist in free state.

Isotopes and Isobars

 Isotopes have the same number of protons (i.e., atomic number), but different number of neutrons and mass number (atomic number + number of neutrons)

 The number of nucleons (both protons and neutrons) in the nucleus is the atom’s mass number, and each isotope of a given element has a different mass number.

Study for civil services :-
 For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively.

 Isobars have the same mass number but different atomic number.

 Isobars are atoms (nuclides) of different chemical elements that have the same number of nucleons.

 Correspondingly, isobars differ in atomic number (or number of protons) but have the same mass number.

 Example: 18Ar40, 19K40