1.2.1.B Elements, Compounds & Mixtures
1.2.1 Elements, Compounds & Mixtures
Compounds
Definition
A compound is a substance made up of two or more elements chemically combined together in a fixed ratio by mass. As a result of this combination, elements lose their own properties and produce new substances (compounds) that have entirely different properties. Compounds can't be broken down into their constituent elements by simple physical methods.
For example, carbon dioxide is formed when elements of carbon and oxygen combine chemically in a fixed ratio of 12:32 or 3:8 by mass. Similarly, water is a compound formed by a chemical combination between hydrogen and oxygen in a fixed ratio of 1:8 by mass.
Classification of Compounds
Ionic Compounds
Ionic compounds do not exist in independent molecular form. They form a three-dimensional crystal lattice, in which each ion is surrounded by oppositely charged ions. These oppositely charged ions attract each other very strongly, as a result, ionic compounds have high melting and boiling points. These compounds are represented by formula units e.g. NaCl, KBr, CuSO4.
Covalent Compounds
The covalent compounds mostly exist in molecular form. A molecule is a true representative of the covalent compound and its formula is called molecular formula e.g. H2O, HC1, H2SO4, CH4.
Mixtures
Definition
When two or more elements or compounds mix up physically without any fixed ratio, they form a mixture.
When two or more elements or compounds mix up physically without any fixed ratio, they form a mixture.
Properties of Mixtures
On mixing up, the component substances retain their own chemical identities and properties. The mixture can be separated into parent components by physical methods such as distillation, filtration, evaporation, crystallization, or magnetization.
Homogenous Mixtures
Mixtures that have uniform composition throughout are called homogeneous mixtures.Example: air, gasoline, ice cream.
Homogenous Mixtures
Whereas, heterogeneous mixtures are those in which composition is not uniform throughout.
Example: soil, rock, and wood.
Whereas, heterogeneous mixtures are those in which composition is not uniform throughout.
Example: soil, rock, and wood.
Difference between Compounds & Mixtures
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