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Types of Chemical Reactions

Deanna Cullen's picture
Wed, 01/15/2014 - 17:23 -- Deanna Cullen

I expect that most high school chemistry teachers assign some type of laboratory related to types of chemical reactions including synthesis, decomposition, single replacement and double replacement reactions. I have used several published versions, but I am sharing my modifications.

For many years, I demonstrated each of the "types" in front of the students before I allowed them to go into the lab and see the results for themselves. I now skip most of the lecture notes and use the discussion time at the conclusion of the lab to cover the material from my old lecture notes. I have found my students are more engaged the material using this format. As an extension, students draw molecular models of each reaction.

Concepts: 

Types of chemical reactions: synthesis, decomposition, single replacement and double replacement

phase notation, how to write a formula equation

Time required: 

20 minutes prep, 40 minutes laboratory, 15-20 minutes discussion

Materials: 

Mossy zinc                                  Copper wire                      Magnesium ribbon

Copper II carbonate                  6 M HCl                              1 M CuSO4

1 M Pb(NO3)2                                            1 M KI                                  Bunsen burner

Crucible tongs                          Microspatula                       Test tubes

Test tube holder                      Test tube rack                    Wood splints

Evaporating dish                      Safety goggles                    10 mL graduated cylinder

Six waste containers

Background: 

I provide a simple definition for each of the types of reactions on the data table page of the lab and as students complete the lab, students compare their balanced equations to the definitions and assign a "type" to each reaction completed in the lab. I set this lab up in stations and students move through it in less than a class period (mine are 60 minutes long). We meet after the procedure portion is complete and discuss what students observed. Some students may have forgotten what a precipitate is and my students have just been introduced to phase notation, so the lab discussion provides an opportunity to cover that content.

Procedure: 

Procedure

Part A

1.        Obtain a piece of copper wire.  Using crucible tongs, hold the wire in the hottest part of a burner flame for 1-2 minutes. 

2.       Examine the wire and note any change in its appearance caused by heating. 

3.       Record your observations.  Place the used copper in the waste container provided.

Part B

1.       Place an evaporating dish near the base of the burner.  Examine a piece of magnesium ribbon.  Using crucible tongs, hold the sample in the burner flame until the magnesium starts to burn.  DO NOT LOOK DIRECTLY AT THE FLAME.  HOLD THE BURNING MAGNESIUM AWAY FROM YOU AND DIRECTLY OVER THE EVAPORATING DISH. 

2.       When the ribbon stops burning, put the remains in the evaporating dish.  Examine this product carefully. 

3.       Record your observations.  Place the product in the waste container and rinse the evaporating dish.

Part C

1.        Place one heaping microspatula of copper II carbonate (CuCO3) in a clean, dry test tube.  Note the appearance of the sample.

2.       Using a test tube holder, heat the CuCO3 strongly for about 2 minutes.  If the CuCO3 begins to rise in the test tube, you can lightly tap the tube and it will fall to the bottom.  Remove the test tube from the flame.  Insert a burning wood splint into the test tube. (If CO2 is present, it will extinguish the flame.) 

3.       Note any change in appearance of the residue in the test tube.  Record all observations.

4.       Carefully place the powder in the waste container and rinse the test tube.

Part D 

1.        Stand a clean test tube in the test tube rack.  Add about 5 ml of 6 M hydrochloric acid (HCl) to the tube.  CAUTION:  HANDLE ACID WITH CARE.  Keep test tube opening away from your body.

2.       Carefully drop a couple small pieces of zinc metal (Zn) into the acid in the test tube.  Observe and record what happens.

3.       Using a test tube holder, invert a second test tube over the mouth of the first.  Remove the inverted tube after about 45 seconds (keep the open end pointed down).  IMPORTANT SAFETY NOTE:  Move the inverted test tube at least two feet from the test tube containing the bubbling solution.Quickly insert a burning wood splint into the mouth of the inverted tube.  (A “pop” indicates the presence of hydrogen gas.)  Note the appearance of the substance in the reaction tube.  (It may take several minutes for the reaction to come to completion.)

4.       Record all observations.  Pour contents of bubbling test tube in the waste container and rinse thoroughly with water. 

Part E

1.        Add about 5 mL of 1 M copper II sulfate solution to a test tube.  Place a small amount of zinc metal in the solution.  Note the appearance of the solution and the zinc before and after the reaction.  (You may have to wait several minutes to see any changes in appearance.) If you cannot see a change in appearance, pour the contents of the test tube into an evaporating dish and observe.

2.       Pour the substance into a waste contaner.  Rinse the glassware.

Part F

1.        Stand a clean test tube in the test tube rack.  Add about 5 mL (measure in a VERY CLEAN graduated cylinder) of lead II nitrate to the test tube.  Note the appearance of the solution.

2.       Measure about 5mL of potassium iodide in a VERY CLEAN graduated cylinder.  Note the appearance of the solution.

3.       Pour the potassium iodide into the test tube containing the lead II nitrate.  Record any observations.

4.      Pour the contents of the test tube down into the waste container.  Rinse the glassware.

Preparation: 

See attached teacher guide

Teacher Document: 
Student Document: 
Attribution: 

I designed the stations based upon demonstrations that I had done for students. There are many similar reaction type labs available.

Chemistry Domain: 
Chemistry Topic: 

Comments

Lowell Thomson's picture
Submitted by Lowell Thomson on

Thanks for posting this Deanna. Your use of the evaporating dish for burning the magnesium ribbon gave me an idea. The ash could be dumped into a beaker with some water and phenolphtheilein indicator. Given the basic nature of mangesium oxide - the product - the indicator should turn pink. In some curricula (IB, for example) the students are expected to know the acid-base nature of oxides. This would be a nice connection between topics to add depth to the discussion.

Lowell Thomson
@ThomsonScience
IB Chemistry Teacher
American International School of Bucharest

Deanna Cullen's picture
Submitted by Deanna Cullen on

That is a great idea, Lowell! I went right in the lab and tried it! I might add in the teacher version (with credit to you, of course), if that is okay?MgO

Lowell Thomson's picture
Submitted by Lowell Thomson on

Thanks for sharing the photo of your results. Very cool. And you are certainly free to use the idea. 

Lowell Thomson
@ThomsonScience
IB Chemistry Teacher
American International School of Bucharest