On the basis of chemical composition, matter can be classified as follows
1. Pure Substances “The substances in which the composition of each part is fixed and fixed are called pure substances.” These include elements and compounds.
Pure substances that can neither be broken down into other components nor made from them by physical or chemical methods.
For example, carbon (diamond, graphite), sodium, potassium, etc. They are generally made up of the same type of atoms. The number of elements known so far is 118, of which 92 elements are natural, while the rest are produced by humans.
The elements can again be divided into the following classes.
Elements which are electropositive and show metallic properties such as natural luster, hardness, malleability, ductility, electrical and thermal conductivity, etc., are called metals. For example, gold, silver, copper, platinum, etc.
Those elements which are electronegative and show non-metallic properties such as lusterlessness, brittleness, softness, electrical and thermal conductivity etc., are called non-metals. For example, oxygen, nitrogen, carbon, etc.
Those elements which have properties of both metals and non-metals are called metalloids. For example, arsenic, germanium, etc.
A pure substance which is obtained by chemical combination of two or more elements in definite proportion is called compound.
Some of the common characteristics of compounds are as follows:
(a) Compounds can be decomposed by chemical methods to recover their parent elements. Example- Water (H2O) is a compound. Because it is formed when hydrogen and oxygen combine in a certain ratio (ratio of 1: 8) and it can be decomposed again into hydrogen and oxygen by passing an electric current.
(b) The properties of compounds are different from those of their constituent elements. Example Hydrogen is a highly flammable gas and Oxygen is helpful in combustion, but the compound formed by their combination i.e. water is used to extinguish fire.
The compounds can be re-divided into two parts.
(A) Inorganic Compounds
Compounds that are formed by the combination of atoms other than carbon. are called inorganic compounds. For example, H, O, NH, etc. Although carbonates, bicarbonates, hydrogen cyanide, etc., are studied with inorganic compounds due to their more similarity of properties to inorganic compounds. These are usually from non-living sources. For example, it is obtained from minerals, rocks, etc.
(b) Organic Compounds
Compounds composed mainly of carbon and hydrogen are called organic compounds. Nitrogen in these. Elements (N), oxygen (O), sulfur (S), etc. are also found. Eg- CH4, C6H6 etc. Most of these are obtained from living sources.
Note that inert gases have the same element and molecular form. Hence the elements of inert gases. Form can also be called compound.
2. Impure Substances/Compound Mixtures
The substance obtained by mixing two or more elements or compounds in any ratio is called a mixture.
Example- air, milk, sea water, etc.
Each of the ingredients present in the mixture retains its identity, that is, on mixing them, they do not interact with each other chemically, otherwise their form or properties or both will change. The components of a mixture can be separated by simple physical methods. Mixtures are of the following two types.
(i) Homogeneous Mixture Homogenous Mixture When the components of a mixture are evenly distributed throughout the mixture, that is, the proportion of the ingredients in the mixture is the same in each part of the mixture, then the mixture is called homogeneous mixture. For example, air is a homogeneous mixture of gases like oxygen (O), nitrogen (N), carbon dioxide (CO), etc. A solution of salt in water and alloys are also homogeneous mixtures. The constituent particles in this type of mixture cannot be seen with the naked eye or with the help of a microscope. Note Air is a homogeneous mixture, but dust particles, smoke particles, etc., are present together in indefinite quantities in the air. Therefore, it is sometimes called a heterogeneous mixture.
(ii) Heterogeneous Mixture Heterogeneous Mixture When the components of a mixture are not evenly distributed in the whole mixture, that is, the components are in each part of the mixture, then such a mixture is called a heterogeneous mixture. Mixture of iron filings, smoke, milk (water and etc. are called heterogeneous mixtures. Such as sand and particles. Smoke, milk (mixture of water and fat), concrete,