Some Basic Concepts of Chemistry

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• Summary

Anything which has mass and occupies space is called matter. For example, book, pen, pencil, water, air, all living beings etc.

Matter can exist in three physical states viz. solid, liquid and gas.

1. Solids have definite volume and definite shape.
2. Liquids have a definite volume but not the definite shape. They take the shape of the container in which they are placed.
3. Gases have neither definite volume nor definite shape. They completely occupy the container in which they are placed. These three states of matter are interconvertible by changing the conditions of temperature and pressure.

At the macroscopic or bulk level, matter can be classified as mixtures or pure substances.

A mixture contains two or more substances present in it (in any ratio) which are called its components.

Types of the mixture:

1. Homogeneous mixture
2. Heterogeneous mixture

Pure Substance: A pure substance or chemical substance is a material that has constant composition and has consistent properties throughout the sample. For example sodium chloride, Diamond etc.

Pure substances can be further classified into elements and compounds.

An element consists of only one type of particles. These particles may be atoms or molecules.

When two or more atoms of different elements combine, the molecule of a compound is obtained. The examples of some compounds are water, ammonia, carbon dioxide etc.