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What is a Mixture?
A mixture is the physical
combination of two or more different substances. We can find in our environment
a mixture of different types.
Examples of Mixtures
There are different kinds of
mixtures available, examples include the following:
Examples of mixture The Earth Crust:
is a mixture of dissolved gases, living organisms and sometimes salts.
a mixture or gases, water vapor and dust particles.
mixture of different hydrocarbons.
Alloys: Contain different elements, e.g., bronze, steel and duralumin.
Coal: A mixture of
coal tar, ammoniacal liquor, coal gas, and coke.
Contain phosphorus, rubber, benzene and sulphur.
Safety Match Heads: Contain KClO3
(which is an
oxidizing agent and therefore makes it possible for the match to start burning,
because it produces oxygen on decomposition immediately when a sufficiently high
temperature has been produced by friction), Fe2O3,
(which acts as
catalyst to decompose KClO3),
powdered glass (which acts to produce friction) and antimony sulphide or sulphur
(which is the combustible substance).
The side of the box, or the striking
surface on the outside of the “book,” is coated with a mixture of powdered
glass, red phosphorus and glue. Friction of the match head against this
prepared surface causes tiny explosions involving the phosphorus and potassium
chlorate. The heat that is thereby liberated ignites the head of the match,
which is not readily ignited by friction alone.
Another example of mixture is
Gun Powder (containing carbon powder, KNO3 and
such as air or a mixture of sugar and water, are homogeneous mixtures;
i.e., it is not obvious to the eye that they are composed of more than one
substance. The constituents are evenly mixed and form a single phase (no
layers are seen). Homogeneous mixtures are usually referred to as solutions.
Other materials, such as sand-sugar mixture, are composed of different kinds of
particles large enough to be individually seen - they are known as
heterogeneous mixtures. The constituents of heterogeneous mixtures are not
evenly mixed, but form layers.
When two or more
liquids are mixed in all proportions to form a homogeneous mixture, they are
said to be miscible, e.g., water and alcohol are miscible. Liquids that
do not intermingle to form solutions are said to be immiscible, e.g.,
water and gasoline. If two liquids A, and B, are only partially miscible, a
limited amount of each will dissolve in the other. If liquid A is present in
excess (i.e., more is present that can dissolve in liquid B), two layers form,
and each layer is a solution. In one layer the solvent is B, and it contains as
much A as can dissolve in it; in the other layer the solvent is A, and it
contains as much B as can dissolve in it. Briefly stated, one layer is
solution of A in B,
other layer is a saturated solution of B in A.
are miscible consist of molecules that are of similar character. Non-polar
liquids, such as carbon disulphide (CS2)
and carbon tetrachloride (CCl4)
are readily miscible with one another, but they will not dissolve in water
because of the high polar nature of water. On the other hand, polar compounds
such as methyl alcohol (CH3OH),
and ethyl alcohol (C2H5
OH) are miscible with one another and with water.
Separation of Mixtures
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