NCERT Summary - Metals Its Physical Properties
Category : 8th Class
Metals and its Physical Properties
Metals and its Physical Properties
(a) Physical Change: A physical change is a change of state only and is not accompanied by an alteration in the chemical composition, weight or chemical properties of any substance, e.g., melting of ice, magnetising a needle, etc.
(b) Chemical Change: A chemical change gives rise to a new substance having composition and properties altogether different from those of the original substance, e.g., radioactive decay, rusting of iron, photosynthesis, etc. Energy is absorbed or released during a chemical change.
PHYSICAL AND CHEMICAL PROPERTIES
(a) Physical Properties: The properties which do not depend on reaction with any other substance, e.g., colour, melting point, boiling point, density, etc.
(b) Chemical Properties: The chemical properties of a substance are those that describe its reactions with other substances.
EMPIRICAL FORMULA
MOLECULAR FORMULA
COLLOIDS
(a) Sol: When a solid is dispersed in a liquid, the particles of a Sol will not settle out.
(b) Gel: In a gel, the liquid contains a colloidal solid dispersed throughout the system, but set in a structure which does not flow, e.g., gelatin, jellies, etc.
(c) Aerosol: The dispersion of either a solid or a liquid in a gas. When the dispersed colloidal particle is solid, the result is smoke and when it is liquid, the result is fog.
(d) Emulsion: When one liquid is dispersed into another in which it is not soluble, e.g., milk, paint, etc.
Properties of Colloids
METALLURGY
RUSTING
ALLOY
ORES
MINERALS
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