2. Compounds
A compound is a substance made up of two or more elements chemically combined in a fixed proportion by weight, e.g. water, NaCl, NH4OH and CO2 etc.
Silicon (Si) is an element and silica (SiO2) is a compound.
Properties of Compounds
Following are the main properties of compounds:
-💧A compound cannot be separated into its components by physical methods.
-💧The properties of a compound are entirely different from those of its constituent elements.
-💧The composition of a compound is fixed, i.e. the constituents are present in fixed proportion by weight.
-💧Compounds have fixed melting point, boiling point etc.
-💧A compound is a homogeneous substance.
MIXTURES
A mixture is a substance which consists of two or more elements or compounds not chemically combined together. e.g. air, milk, ink, brine, lime water, glass, paints, soil, tood, wood, kerosene etc.
There are two types of mixtures, which are as follows
1. Homogeneous Mixture or Solution
A homogeneous mixture has a same composition throughout its mass. It has no visible boundaries of separation between the various constituents, e.g.
solution of sugar in water, alloy, solution of salt in water, a mixture of alcohol and water etc.
2. Heterogeneous Mixture A heterogeneous mixture does not have a uniform composition throughout its mass. It has visıble boundaries of separation between the various components, e.g. solution of K2Cr2O7 in
water, solution of CaCO3 in water, solution of oil in water, gun powder, soil, etc.
-💧Note A mixture which boils at a definite temperature and distils over without any change in composition is called azeotropic mixtures. e.g. ethanol-water, acetone-benzene, benzene-chloroform etc.
Properties of a Mixture
Following are the main properties of a mixture:
•A mixture can be separated into its components by physical methods like, filtration, evaporation, sublimation, distillation, magnet etc.
•A mixture shows the properties of all the constituents present in it. Energy is usually neither given out nor absorbed during the preparation of a mxture.
•The composition of a mixture is variable, i.e. the constituents can be present in any proportion by weight.
•A mixture does not have a definite melting point, boiling point etc. (except azeotropic mixture).
To be continue...🌺
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