TYPES OF CHEMICAL REACTIONS_2_

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					                               TYPES OF CHEMICAL REACTIONS

INTRODUCTION

Chemical changes are a result of chemical reactions. All chemical reactions
involve a change in substances and a change in energy. There are so many
chemical reactions that it is helpful to classify them into 4 general types which
include the following:

SYNTHESIS REACTION
In a synthesis reaction two or more simple substances combine to form a more
complex substance. Two or more reactants yielding one product is another way
to identify a synthesis reaction.
For example, simple hydrogen gas combined with simple oxygen gas can
produce a more complex substance, water!


The chemical equation for this synthesis reaction looks like:



DECOMPOSITION REACTION
In a decomposition reaction a more complex substance breaks down into its
more simple parts. One reactant yields 2 or more products. Basically, synthesis
and decomposition reactions are opposites.
For example, water can be broken down into hydrogen gas and oxygen gas. The
chemical equation for this decomposition reaction looks like:


SINGLE REPLACEMENT REACTION
In a single replacement reaction a single uncombined element replaces another
in a compound. Two reactants yield two products. For example when zinc
combines with hydrochloric acid, the zinc replaces hydrogen. The chemical
equation for this single replacement reaction looks like:



DOUBLE REPLACEMENT REACTION
In a double replacement reaction parts of two compounds switch places to form
two new compounds. Two reactants yield two products. For example when silver
nitrate combines with sodium chloride, two new compounds--silver chloride and
sodium nitrate are formed because the sodium and silver switched places. The
chemical equation for this double replacement reaction looks like:


Info taken from http://www.usoe.k12.ut.us/CURR/Science/sciber00/8th/matter/sciber/chemtype.htm for purpose of
demonstrating how to write an introduction.




Types of Reactions Design Lab                                                                                   CHEM
PURPOSE

The purpose of this experiment is to see if the rules for predicting reaction
products really work and to identify the different types of reactions while
predicting their products.

HYPOTHESIS

If rules for predicting products are used and evidence of a chemical reaction are
observed then the rules for predicting products do work.

If magnesium reacts with silver nitrate then the products will be silver and
magnesium nitrate.

If copper(II) carbonate is heated then the products will be copper(II) oxide and
carbon dioxide.

If magnesium is heated in the presence of oxygen then the product will be
magnesium oxide.

If ________________ reacts with __________________ then the products will
be ______________________ and _______________________.

If __________________ is mixed with _________________ then no reaction will
take place.

MATERIALS




SAFETY

See MSDS

PROCEDURE

PART A



Types of Reactions Design Lab                                                       CHEM
   1. A 2-cm piece of magnesium metal was obtained and cleaned with a piece of
      steel wool until shiny.
   2. Two eye droppers of silver nitrate were placed in a test tube.
   3. The strip of magnesium metal was placed into the test tube and the reaction was
      observed for several minutes. Observations were recorded.
   4. The solution was disposed in the waste beaker provided by the teacher.


PART B
  5. One scoop of copper(II) carbonate, CuCO3, was placed in a clean test tube. The
     appearance of the sample was noted.
   6. The Bunsen Burner was lit using a gas lighter.
   7. The CuCO3 was heated by moving it back and forth gently over the burner using
      a test tube holder. THE MOUTH OF THE TEST TUBE WAS AIMED AT AN
      ANGLE AWAY FROM OTHERS.
   8. After heating, another group member ignited a wood splint and quickly placed the
      burning splint into the test tube to test for the presence of CO2 gas.
   9. Observations were recorded, including the results of the CO2 test. THE
      BURNER REMAINED LIT FOR PART C.

PART C
  10. A watch glass was placed next to the burner.

   11. A 5-cm piece of magnesium metal was obtained and cleaned with a piece of
       steel wool until shiny.

   12. Using crucible tongs, the magnesium was held in the burner flame until the
       magnesium started to burn. The burning magnesium was held directly over the
       watch glass.

   13. When the magnesium stopped burning the remains were placed on the watch
       glass. The burner was turned off. The product was examined thoroughly and
       observations were recorded.

PART D

   14. Procedure for this part was designed by students. It should be written in past
       tense and complete sentences.


OBSERVATIONS

Table 1: Chemical Reactions and their Products
Reactants Before       During      After       Products                  Type of
                                                                         reaction
Magnesiu      -                 -liquid   -liquid was     Silver and     Single


Types of Reactions Design Lab                                                            CHEM
m and         magnesiu          began to    transparent       magnesiu     Displacement
silver        m was             become      -precipitate      m nitrate
nitrate       malleable,        transparen was brittle
              lustrous,         t
              silver,           - silver
              solid,            precipitate
              smooth,           developed
              opaque,           on solid
              thin, soft,       piece of
              flexible          metal
              -silver           -some
              nitrate was       precipitate
              a liquid,         was black
              translucent
              , slight
              grey, thin
Heated        -green            -solid         -black solid   Copper(II)   Decompositio
copper (II)   solid,            began to       - glowing      oxide and    n
carbonate     opaque,           turn black     splint         carbon
              crystalline,      from           extinguishe    dioxide
                                bottom to      d
                                top
                                -became
                                fluid like
                                while
                                heated
Magnesiu      -                 -flame first   -solid is      Magnesiu     Synthesis
m and         magnesiu          turned         white and      m oxide
oxygen        m was             orange,        brittle
              malleable,        then bright
              lustrous,         yellow.
              silver,           -solid then
              solid,            glowed
              smooth,           bright
              opaque,           white
              thin, soft,
              flexible

                                                                           Double
                                                                           Displacement


                                                                           No reaction




Types of Reactions Design Lab                                                             CHEM
DISCUSSION


During the lab, there were four different types of reactions observed. The first
reaction between magnesium and silver nitrate was a single displacement
reaction. This reaction took place since a silver precipitate was observed forming
on the solid metal.

The second reaction took longer to notice a chemical change. When copper(II)
carbonate was heated it began to change from green to black. To see if a gas
was present, a glowing splint was placed in the mouth of the test tube. The
glowing splint was immediately extinguished meaning that carbon dioxide was a
product. The other product for this decomposition reaction was copper(II) oxide.

The third reaction was a synthesis reaction as a solid piece of magnesium was
reacted with oxygen to form only one product, magnesium oxide. It was very
evident that a chemical reaction took place as a blinding white light was
produced by the burning magnesium. The product, magnesium oxide, was
observed as a white brittle solid.

The last two reactions were double displacement reactions…

(students should discuss the reactions they chose to do)



Questions should be answered in this section using complete sentences.


The following sources of error occurred during the duration of the lab:

Table 2: Sources of Error

          Error                      Results affected            How to Avoid
1. Changing eye                 If the eye droppers used   After using an eye
droppers in solutions           for the double             dropper, place in the
                                displacement reactions     garbage and use a new
                                were mixed up then the     one for a different
                                solutions would be         solution.
                                contaminated and results
                                would be incorrect (ie.
                                Maybe no reaction would
                                take place)
2. Taking too long to           If too much time was       One person should heat
place the glowing splint        taken to place the         the copper(II) carbonate



Types of Reactions Design Lab                                                         CHEM
in the mouth of the test        glowing splint in the       while another person
tube                            mouth of the test tube      place the glowing split in
                                with copper(II) carbonate   the test tube immediately
                                then it is possible that    after heating and colour
                                carbon dioxide would not    change observed.
                                have been observed to
                                be a product
3. Not polishing the            The coating on the          Rub the piece of
protective coating off the      magnesium could have        magnesium with steel
piece of magnesium              hindered the reaction of    wool for a long period of
                                magnesium with either       time (i.e. 1 minute)
                                silver nitrate or oxygen

CONCLUSION


In conclusion, four different types of reactions took place and the rules for
predicting products did in fact work.




Types of Reactions Design Lab                                                            CHEM

				
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