EXPERIMENT ON SYNTHESIS REACTIONS

INTRODUCTION: 

In a synthesis reaction two or more simple substances are chemically combined to form a more complex substance. One of the substances, usually a metal, will have the tendency to lose electrons to become stable and form positive ions. The other substance, usually a nonmetal, will have the tendency to gain electrons to become stable and form negative ions. When the reaction occurs the metal loses electrons and the non metal gains the electrons. The positive and negative ions formed attract and Join together to form clusters of tons called "crystals".

+ - + - + - + -       Note that the positive ions are surrounded by negative ions

- + - + - + - +       and the negative ions are surrounded by positive tons.

+ - + - + - + -       This pattern repeats in three dimensions.

The general equation for synthesis reactions is A + B--------- > AB + energy

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elements compound

In this experiment, two synthesis reactions will occur. In the first, the substances to be combined will be the elements copper and oxygen. In the second, the elements will be iron and oxygen. These elements will not react immediately when mixed together. They must be heated to initiate a reaction. Once the reaction is started, some of the energy produced will be used to continue the reaction until it is completed.

PURPOSE:           The purpose of this experiment is to investigate synthesis reactions.

HYPOTHESIS:    If two elements are heated, a synthesis reaction will occur and an ionic compound will be formed.

SAFETY PRECAUTIONS: The Bunsen burner produces a clear blue flame at a temperature of about 500 ^oC. We must exercise extreme caution around these flames because they are difficult to see and can cause severe burns. Bunsen burners are fuelled be an explosive gas called methane. Excessive amounts of unburned methane leaking into the lab could cause an explosion. For this reason we do not light the Bunsen Burner until we need it. When we light the Bunsen burner, we must light it immediately after turning on the gas and turn it off as soon as we are done with it.

The reaction of Iron and Oxygen produces a great deal of heat. Do not touch the glowing Iron with your hands. If the reaction does not appear to be stopping run the steel wool under cold water in the sink.

Treat any burns by running under cold water for several minutes and send your lab partner to inform the teacher.

PROCEDURE:

Part 1: Copper and Oxygen

1.  Obtain a piece of copper wire about 5 cm long, a small piece of steel wool, and a pair of flask tongs.

2.  Use the steel wool to clean the copper wire.

3.  Record your observations of the copper wire.

4.  Light the Bunsen burner.

5.  Use the tongs to hold the copper at the tip of the inner cone of the flame for several minutes.

6.  Turn the Bunsen burner off as soon as you are finished.

7.  Allow the copper to cool and record your new observations of the copper wire.

  Part 2: Iron and Oxygen

              1. Obtain a 9 volt battery.

              2. Record your observations of the steel wool.

              3. Hold the steel wool with the tongs and touch the steel wool to the terminals of the battery.

              4. Observe the reaction.

              5. If the reaction gets out of hand, run the steel wool under cold water in the sink.

              6. Allow the steel wool to cool and record your new observations of the steel.

OBSERVATIONS: Write a paragraph for each reaction. Be sure to describe what the metal looked like before, during, and after the reaction. Include any evidence that energy was released.

RELATED QUESTIONS:

1.   Where did the oxygen that was required for these reactions come from?

2.   What was produced when the copper was heated over the Bunsen burner? Do you know the exact name of the compound? Why or why not?3.Why is it necessary to close the air vents on the Bunsen burner before trying to light it?

4.   Why is the copper heated in this experiment?

5.   What experimental evidence suggests that the copper was involved in a chemical reaction?

6.   Write a word equation for the reaction of the copper.

7.   What was produced when the iron (steel wool) touched the battery? Do you know the exact name of the compound? Why or why not?

8.   Why was the iron touched with battery?

9.   Iron oxide is rust. Did the product look like rust? Explain why it might not look like rust.

10  The steel wool became very hot when it reacted. Why don’t cars get hot when they rust?

11. What experimental evidence suggests that the steel wool was involved in a chemical reaction?

12. Write a word equation for the reaction of the iron.