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					In chemistry, a mixture is a material system made up by two or more different substances which are
(mixed) together but are not combined chemically. Mixture refers to the physical combination of two or
more substances the identities of which are retained. The molecules of two or more different
substances are mixed in the form of alloys, solutions, suspensions, and colloids.Mixtures can be either
homogeneous or heterogeneous


Homogeneous (chemistry)
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A substance that is uniform in composition is a definition of homogeneous in Chemistry. This
is in contrast to a substance that is heterogeneous.[1] The definition of homogeneous strongly
depends on the context used. In Chemistry, a homogeneous suspension of material means that
when dividing the volume in half, the same amount of material is suspended in both halves of the
substance. However, it might be possible to see the particles under a microscope. In Chemistry,
another homogeneous substance is air. It is equally suspended, and the particles and gases and
liquids cannot be analyzed separately or pulled apart.

[edit] Homogeneity of mixtures
In Chemistry, mixtures may be homogeneous. In other words, mixtures have the same
proportions throughout a given sample or multiple samples of different proportion to create a
consistent mixture. However, two homogeneous mixtures of the same pair of substances may
differ widely from each other and can be homogenized to make a constant. Mixtures can be
characterized by being separable by mechanical means e.g. heat, filtration, gravitational sorting,
etc.[2]

[edit] Solutions

A solution is a special type of homogeneous mixture. Solutions are homogeneous because, the
ratio of solute to solvent remains the same throughout the solution even if homogenized with
multiple sources, and stable because, the solute will not settle out, no matter how long the
solution sits, and it cannot be removed by a filter or a centrifuge.[3] This type of mixture is very
stable, i.e., its particles do not settle, or separate. As homogeneous mixture, a solution has one
phase (liquid) although the solute and solvent can vary: for example, salt water. In chemistry, a
mixture is a substance containing two or more elements or compounds that are not chemically
bound to each other but retain their own chemical and physical identities; - a substance which
has two or more constituent chemical substances. Mixtures, in the broader sense, are two or more
substances physically in the same place, but these are not chemically combined, and therefore
ratios are not necessarily considered.

Heterogenous Mixtures
When two or more substances are combined together but not in any particular or fixed proportion
then it is called as a mixture. A mixture can be classified into two categories - homogeneous
mixture and heterogeneous mixture. A mixture that has a same composition throughout with
uniform appearance is called as homogeneous mixture. A homogeneous mixture is also known as
a solution. A heterogeneous mixture on the other hand is made of more than one phase and can
be separated physically. They also do not have a uniform composition throughout the mixture.

Heterogeneous Mixture Explained

Suspensions and emulsions are two special types of heterogeneous mixture. A suspension is a
mixture of solids and liquid in which the solids do not dissolve in the liquid solution. When a
suspension is allowed to stand for some time and left undisturbed, the solid particles settle at
bottom of the container. An example of suspension is sand in water and clay in water. An
emulsion is a special type of suspension where a mixture consists of two liquids which do not
mix together. When two such liquids are kept together they do not mix, no matter how much you
try to do so by shaking or stirring. They will ultimately settle into two layers one above the other
when left undisturbed for considerable period of time. Examples of emulsions are kerosene and
water and a mixture of oil and water. Both suspensions and emulsions show the Tyndall effect.

The definition of a heterogeneous mixture is one which does not have a uniform composition and
has visible sharp boundaries. Heterogeneous mixture are those in which the substances are not
distributed evenly. They usually involve a mixture of a solid in a solid. The main difference
between solutions and mixture is that a solution can only be separated into its original
components by chemical means whereas a mixture can be separated by mechanical means. For
example, if you mix sugar granules in a glass of water, the sugar granules completely dissolves
in the water. This sugar solution is an example of homogeneous mixture. Now if you want to
separate the sugar crystals from the sugar solution it is not possible to do so by mechanical
means. For this you have to first boil the sugar solution so that all the water evaporates into the
air and the sugar crystals will be left behind.

Now let us take the example of a mixture. If you have a heterogeneous mixture of two substances
say, sand and iron fillings then you can easily separate them by mechanical means. This can be
done by using a magnet to sift the iron fillings away. All you will be left behind is the sand. Thus
a simple mixture can be separated by mechanical means. Some other mechanical means by
which a mixture can be separated are sifting, filtration and by using gravity.

Heterogeneous Mixture Examples

Now that we have answered the question as to what is heterogeneous mixture in chemistry, let us
list some examples of heterogeneous mixture.

      Sand in water
      Smoke
      Blood
      Chicken soup
      Protoplasm
   Silt in water
   Tomato juice
   Clouds
   Vinegar in oil
   Air
   Mayonnaise
   Ice tea
   Concrete
   Wood
   Oil paint
   Hand cream
   Salad dressing
   Soil
   Chocolate chip cookie
   Muddy water
   sugar and cornstarch
   Salt and iron fillings
   Salt and Sugar mixture
   Mixture of different types of cereals
   Mixture of stones in soil
   Trail mix
   Lentil soup
   Peanut butter
   Aerosol spray

				
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