Question

Define a pure substance. How many types of pure substances do you know?

Answer 1

Hint:We have to remember that in general physical matter is classified as solid, liquid and gases. The types of matter
-Solid
-Liquid
-Gases
Solids further classified as mixture and pure substances.
-The types of solids
-Mixture
-Pure compound

Complete step by step answer:
We must need to know that the pure substance is nothing but matter formed by the same kind of atoms or molecules. Once pure substance is composed of similar moiety.
Pure substance is classified as an element and compound. Pure compound classification is based on the formation of substances.
Types of pure substance
-Element
-Compound
We need to know that the element is nothing but made up of a single kind of atom. Element is further classified as monatomic, diatomic, triatomic and polyatomic.
Types of element
Monoatomic
Diatomic
Triatomic
Polyatomic
We must know that the monatomic means a single atom present in an element. Example of monoatomic element is $Na(sodium)$
As we know that the diatomic means two same atoms combined to form an element. Example for diatomic elements is ${N_2},{O_2},C{l_2}etc$(nitrogen, oxygen, chlorine etc.)
Triatomic means three same atoms combined to form an element. Example for triatomic element is ozone ${O_3}$
Polyatomic means elements in nature form more than three or more atoms. Example for polyatomic is sulphur${S_8}$
We need to know that the compound means a molecule is made up of two or more atoms with different atoms by forming bonds to form stable bonds. In this formation various kinds of bonds are used to form compounds by atoms.
There three kind of bonds are forming in compound are
-Ionic bond
-Covalent bond
-Coordinate bond
Ionic bonds are formed between cation and anion. The compound formed by ionic bonds is known as ionic compound. Example sodium chloride$(NaCl)$.
Covalent bonds are formed by mutual sharing of electrons in between atoms. The compound formed by covalent bonds is known as covalent compound. Example for covalent compound is methane$(C{H_4})$
Coordinate bond is formed by sharing a lone pair of electrons from one atom to another atom. The compound formed by coordinate bond is known as the coordinate compound.

Note:
We have to remember that copper metal is an example for elements and copper sulphate is an example for compounds. Compounds are more stable than mixtures. In compounds, ionic compounds are more stable than other compounds. Ionic bond is stronger than covalent and coordinate bond. Pure substance is free flow of solid. In liquid also forms a pure substance. In a mixture classified as heterogeneous and homogeneous mixture. Homogeneous mixture means mixed with two or more compounds to form a single form of solid or liquid. Heterogeneous mixture means mixed with two or more compounds to form more than a single form of solid or liquid.