Some Basic Concepts of Chemistry

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Matter is anything that has mass and occupies volume. Physical classification of matter is based on state: solids, liquids, and gases. Solids have definite shape and volume, liquids have definite volu…

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An element is a pure substance that cannot be broken into simpler substances by ordinary physical or chemical methods. A compound is a pure substance formed by chemical combination of two or more diff…

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In a homogeneous mixture, the components are uniformly distributed throughout the sample. In a heterogeneous mixture, the components are not uniformly distributed and different parts may have differen…

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Water is a compound because hydrogen and oxygen are chemically combined in a fixed mass ratio of 1:8 and can be separated only by chemical means. Air is a mixture because its gases are physically mixe…

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Physical properties can be measured without changing the identity of the substance. Examples include colour, odour, density, melting point, boiling point, and specific heat. Chemical properties involv…

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During any physical or chemical change, the total mass of products is always equal to the total mass of reactants. It is verified in a special H-shaped Landolt's tube using the reaction: AgNO3(aq) + N…

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CaCO3(s) → CaO(s) + CO2(g) This is a decomposition reaction. The reaction shows conservation of mass because the total mass of products equals the mass of the reactant.

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A chemical compound, no matter from which source it is obtained, always contains the same elements combined together in the same definite proportion by mass. For example, water always contains hydroge…