A
mixture is composed of a variety of atoms. These atoms are usually not bound
together in a chemical way. Mixtures are categorized into two broad categories;
homogenous and heterogeneous. In a homogenous mixture, all the portions that
make the mixture are somewhat similar and once the mixture has formed, it would
be almost impossible to tell the presence of two elements. The example of sugar
and water is a kind of a homogenous mixture. A heterogeneous mixture on the
other hand is one in which the atoms that comprise the mixture are dissimilar.
Homogenous mixtures are often referred to as solutions. This implies that one
can actually tell the presence of two or more elements just by observation of
with a naked eye. An example would be a mixture of sand and sugar (Aldridge,
2009).
On the other hand, a compound
consists of a variety of elements which have been bound together by some
chemical process. This implies that in a mixture, it is possible to physically
locate the different atoms and inmost of the cases one can actually separate
the two by a purely physical procedure. In compounds however, it may not be
possible to see the different elements and separation of the constituent
elements can only be achieved through some chemical process. In fact, the separation of compounds would
sometimes lead to the destruction of one of the elements.
The constant composition law is the
best approach to understanding the difference between the two. According to the
law, mixtures don’t have a constant composition unlike the compounds which have
a constant composition. For instance, water will always be composed of 11.2
percent hydrogen and an oxygen percentage of 88.8. That means that water is a
compound. But if you had two elements together like water and milk, the
composition would vary depending on the person mixing them. This would be a
good example of a mixture.
How to tell the
difference
If
you had a pure substance and you needed to tell whether it was a compound or a
mixture, you will need to establish whether the substance comprised of
separable elements. Even though pure substances are almost similar to
homogenous mixtures, the difference is that a pure substance will show
uniformity of composition all through while a mixture might have a discrepancy
here and there. The important rule to apply is that pure substances can not be
further broken down into other substances unless their properties are changed
first and this can only happen in a chemical process (Aldridge, 2009).
Subjecting
the substance to some physical separation tests will suffice to establish
whether or not it is a pure substance. This would include such tests as
dissolving in water, evaporation, filtering, freezing or melting depending on
the state of the substance. If none of the physical procedures can separate
elements that have formed the substance, then it will be confirmed to be a pure
substance.
Ionic and covalent
bonds
Atoms
usually react in a chemical process to join to form compounds. The force that
holds them together is usually referred to as bonds. These bonds can either be
ionic or covalent bonds. When the ions with dissimilar charges attract to form
the bond between the different atoms, the n the bonds are referred to as ionic.
Consequently, if the ions that are similar are the ones that are responsible
for the bond formation, the bonds will be described as covalent bonds. Usually, the inorganic are said to be
of ionic bonds. Sodium chloride is one such example. It is formed by reacting
sodium (Na) and Chlorine (Cl) to get sodium chloride (NaCl). Unlike is the case
for the covalent bonds, sodium does not share electrons. On the contrary, it
gives up its extra ion to chlorine resulting in the formation of the ionic bond.
Covalent bonds usually form organic compounds. In such a scenario, the
different elements combine by sharing the ions. An example of such a bond is one
found in methane demoted as CH4. The different electrons in the Hydrogen
molecule share the carbon molecule to form a covalent bond (Aldridge, 2009).
Ionic
compounds
These
compounds form as a result of a metal from the left side reacting with a non
metal from the right of the periodic table. They are also referred to as the
metals. They are usually described as being electropositive. This means that
they easily lose their delocalized electrons. Metals will therefore react by
loosing electrons which makes them to be positively charged. This makes them
form ionic compounds. Some examples are magnesium oxide and lithium hydride.
Ionic bonds can be formed in two different ways. When the electrons are shared
equally, the resulting bond can be described as non-polar. If however, the
electrons have not been shared equally, then the bond that forms will be formed
as a polar bond. Sodium chloride is an example of an ionic bond. Sodium reacts
by releasing its delocalized electron to chlorine thereby forming an ionic bond
(Aldridge, 2009).
Covalent compound
Covalent
bonds are formed when nonmetals from the right side of the periodic table bond
with each other. The elements that are found on the right side of the periodic
table are described as being electronegative. It means that they easily accept
electrons. They are also referred to as the non-metals. When these elements react by accepting electrons,
they become negatively charged ions. The term anion is therefore used to refer
to them. An example of a covalent bond can be seen in the methane (CH4)
compound. The different electrons in the Hydrogen molecule share the carbon
molecule to form a covalent bond (Sadish, 2010).
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