Chemical Reactions Term Paper

This essay has a total of 2036 words and 7 pages.

Chemical Reactions

Chemical reactions are the heart of chemistry. People have always known that they exist.
The Ancient Greeks were the firsts to speculate on the composition of matter. They thought
that it was possible that individual particles made up matter. Later, in the Seventeenth
Century, a German chemist named Georg Ernst Stahl was the first to postulate on chemical
reaction, specifically, combustion. He said that a substance called phlogiston escaped
into the air from all substances during combustion. He explained that a burning candle
would go out if a candle snuffer was put over it because the air inside the snuffer became
saturated with phlogiston. According to his ideas, wood is made up of phlogiston and ash,
because only ash is left after combustion. His ideas soon came upon some contradiction.
When metal is burned, its ash has a greater mass than the original substance. Stahl tried
to cover himself by saying that phlogiston will take away from a substance's mass or that
it had a negative mass, which contradicted his original theories. In the Eighteenth
Century Antoine-Laurent Lavoisier, in France, discovered an important detail in the
understanding of the chemical reaction combustion, oxigine (oxygen). He said that
combustion was a chemical reaction involving oxygen and another combustible substance,
such as wood.John Dalton, in the early Nineteenth Century, discovered the atom. It gave
way to the idea that a chemical reaction was actually the rearrangement of groups of atoms
called molecules. Dalton also said that the appearance and disappearance of properties
meant that the atomic composition dictated the appearance of different properties. He also
came up with idea that a molecule of one substance is exactly the same as any other
molecule of the same substance. People like Joseph-Lois Gay-Lussac added to Dalton's
concepts with the postulate that the volumes of gasses that react with each other are
related (14 grams of nitrogen reacted with exactly three grams of hydrogen, eight grams of
oxygen reacted to exactly one gram of hydrogen, etc.)Amedeo Avogadro also added to the
understanding of chemical reactions. He said that all gasses at the same pressure, volume
and temperature contain the same number of particles. This idea took a long time to be
accepted. His ideas lead to the subscripts used in the formulas for gasses.From the work
of these and many other chemists, we now have a mostly complete knowledge of chemical
reactions. There are now many classification systems to classify the different types of
reactions. These include decomposition, polymerization, chain reactions, substitute
reactions, elimination reactions, addition reactions, ionic reactions, and
oxidation-reduction reactions.Decomposition reactions are reactions in which a substance
breaks into smaller parts. As an example, ammonium carbonate will decompose into ammonia,
carbon dioxide, and water. Polymerization reactions are reactions in which simpler
substances combine to form a complex substance. The thing that makes this reaction unusual
is that the final product is composed of hundreds of the simpler reagent (a substance that
contributes to a chemical reaction) species. One example is the polymerization of
terephthalic acid with ethylene glycol to form the polymer called Dacron, a fibre, or
Mylar, in sheet form:nH2OC(C6H4)CO2H nHOCH2CH2OH -> [...OC(C6H4)CO2CH2CH2O...]n 2nH2Oin
which n is a large number of moles. A chain reaction is a series of smaller reactions in
which the previous reaction forms a reagent for the next reaction. The synthesis of
hydrogen bromide is a good example: H2 Br2 -> 2HBrThis is a simple equation that doesn't
properly prove the reaction. It is very complex and starts with this: Br2 -> 2Br The next
three reactions are related and should be grouped together. A substation reaction is a
reaction in which a substance loses one or more atoms and replaces them with the same
number of atoms of another element from another substance. Here is the example of
chloroform that reacts with antimony triflouride:CHCl3 SbF3 -> CHClF2An elimination
reaction is a reaction in which a compound is broken into smaller parts when heated. Here
is an example when the same substance is heated and goes through another reaction:2CHClF2
-> C2F4 2HClAn addition reaction is a reaction in which atoms are added to a molecule.
If the added atoms are hydrogens, then the reaction is called a hydrogenization reaction.
If Oleic acid is hydrogenized, this what you get:C18H34O2 H2 -> C18H36O2 Another
reaction is called an ionic reaction. It occurs between two ions and can happen very
quickly. For example, when silver nitrate and sodium chloride are mixed you get silver
chloride:AgNO3 NaCl -> AgCl NaNO3The last type of reaction is called
oxidation-reduction. These are reactions that involve a change in oxidation number. It is
a reaction if the oxidation number goes up. It is a reduction reaction if the oxidation
number goes down.It is now known that there are three types of chemical reactions. They
are classified into three types: exoergic (exothermic), endoergic (endothermic), and
aergic (athermic). In these cases, energy is supplied, but the different types of
reactions initiate the energy differently.Exoergic, or exothermic, reactions release
energy during the reaction. Combustion is one of the major reactions that do this. The
burning of wood, or any other fuel, gives off heat, and the burning of glucose in our
bodies gives off both energy and heat.Endoergic, or endothermic, reactions absorb energy
during the reaction. The melting of an ice cube is an example of an endothermic
Continues for 4 more pages >>