IIT/FIELD MUSEUM – High School Transformation Project
Classifying Chemical Reactions
Glencoe Chemistry: Matter and Change
Unit 3 Bonding and Reactions
Chapter 10 Chemical Reactions
Section 10.2 Classifying Chemical Reactions
Context of the Lesson
After students learn what chemical reactions are and how to express them in chemical
equations, they need to learn to identify the five (5) fundamental types of chemical equations:
synthesis, decomposition, single-replacement, double-replacement and combustion. This
lesson provides students with a guided-inquiry experience that allows them to understand the
types of chemical reactions by leading them through several exercises using analogies. After
this lesson, students will be ready to learn aqueous chemical reactions.
Main Goals & Objectives
Students will sort mathematical equations into categories then repeat the exercise with
chemical equations. Afterwards, students will listen to a story with analogies to chemical
changes and then create their own analogy stories. From performing these activities, students
will be able to:
 Classify chemical reactions as synthesis, decomposition, single-replacement, doublereplacement or combustion reactions.
 Identify the characteristics of the fundamental types of chemical reactions.
 Develop models for chemical reactions and identify the limitations of the models.
Nature of Science: Integrated Theme
 Explain that scientists’ creativity influences their doing inquiry so they may have
different observations and interpretations of the same phenomena.
 Explain that scientists’ background knowledge influences their doing inquiry so they may
have different observations and interpretations of the same phenomena.
Scientific Inquiry: Integrated Theme
 Explain that scientific investigations all begin with a question, but do not necessarily test
a hypothesis.
 Explain that there is no single scientific method and provide at least two different
methods.
 Explain that inquiry procedures are guided by the question asked.
 Explain that all scientists performing the same procedures may not get the same results.
 Explain that inquiry procedures can influence the results of an investigation.
 Explain that research conclusions must be consistent with the data collected.
General Alignment to Standards
STATE GOAL 12: Understand the fundamental concepts, principles and interconnections of
the life, physical and earth/space sciences
C. Know and apply concepts that describe properties of matter and energy and the
interactions between them
 12.C.5a Analyze reactions (e.g., nuclear reactions, burning of fuel,
decomposition of waste) in natural and man-made energy systems.
Materials
Per pair of students:
 “Mathematical Equations Challenge” sheet*
 “Chemical Equations Challenge” sheet*
 Scissors
*Teacher note: The two equation sheets should be copied on differently colored paper because
although, they will be cut up into pieces, they still need to be distinguishable.
Per student:
 Notebook
 Reaction Types Worksheet
Safety
 Remind students that lab materials are to be used ONLY as directed
 Review safety issues regarding scissors and other sharp objects
The Lesson
Day One
Bell Ringer:
On the board or overhead, write: “We humans classify many things—living organisms, food
groups, types of cars, just to name a few. What is the purpose of all this classifying? Write
three reasons that classification is useful.” Have students think, pair, share their ideas.
Activity
Assign students to teams of two and distribute the “Mathematical Equations Challenge”
worksheet (one per team).
Instruct students to cut the sheet into strips, with one equation on each strip. Then sort the
equations into groups based on their observations. Circulate among the students and observe
their equation groupings. If students seem really confused, suggest that they look for five
possible groups or not at the actual numbers, but at the way the equations look overall.
When a team has successfully grouped their equations into five groups (which will look
remarkably like synthesis, decomposition, etc.), have them explain their groupings. Then give
them the “Chemical Equations Challenge” worksheet and instruct them to repeat the
procedure done with the math equations. Indicate that they use their groups of mathematical
equations to help them sort the chemical equations. Almost all students will classify the
equations into the five (5) fundamental reaction types.
Once a team has successfully grouped the chemical equations, direct them to write the
chemical equations in their notebooks in the same groupings as the strips of paper. They should
then prepare to explain to the class how they developed their classification schemes.
As a class discussion, ask teams to explain the development of their classification schemes.
Encourage all students to share their thought processes and point out that their different
methods were influenced by each student’s creativity and interpretation. Indicate that this is a
normal aspect of the nature of science. Also, point out that the students combined their
previous classifying skills with new knowledge about chemical reactions to develop their
classification schemes. Indicate that this is a common aspect of the scientific inquiry.
Homework
Read Section 10.2 (pages 284-291) and match the five classes of reactions with the five groups
you made in class. On the “Reaction Types Worksheet,” identify each reaction by its class.
Day Two
Bell Ringer:
On the board or overhead, write: “Last night you read about five types of chemical reactions.
How would you describe each one in a sentence? Write a description of what happens in each
type of reaction: synthesis, decomposition, single replacement, double replacement and
combustion.”
Review
Check in the worksheet students completed for homework, then go over the correct answers as
students check their work. An answer presented via the overhead projector can speed up this
process. Discuss any items that the students found difficult and provide clues to identifying the
five reaction types as necessary.
Example clues:
one product—synthesis
one reactant—decomposition
one lonely element and one compound on each side—single replacement
two compounds on each side—double replacement
oxygen as reactant, oxides as products—combustion
Tell students that you are going to read them a story. Ask them to put down their pens and
relax. (You may wish to dim the lights and light a candle to “set the mood” for the romantic
story. You may also enhance your “street creed” by acknowledging that the story is very hokey,
but that it does the job!)
The Story
One day, as you are walking out of school after your last class, you see the most
attractive person you’ve seen in a long while. You ask your friends if they know who this
person is. One of your friends knows the person and tells you the attractive person’s name. In
fact, your friend is good friends with this person’s friend and offers to find out what lunch
period this new apple of your eye is in. The next day at lunch, your friend takes you over to the
table where the person is sitting and introduces you. You and your friend sit down with the
attractive person and friend, and the four of you talk and enjoy lunch together. You find that
not only is this person cute, but funny and enjoyable to be around. The person seems to enjoy
your company, too, and you exchange e-mail addresses and phone numbers.
That night, you get a phone call from the person and talk for a while. You enjoy it and
learn that the two of you have a lot in common. Before long, the two of you are a couple, and
you decide to go to the next school dance together. You’re so excited—this person is so much
fun to be around that you’re sure it’s going to be a great night.
The day of the dance comes and everything is perfect—your clothes, your date’s
clothes, the decorations, the music—it’s all great and you’re having a terrific time. The DJ puts
on a slow song and you find that you really like dancing in your date’s arms. The next song is a
fast one and you and your date join a group of friends dancing nearby. For part of the song, you
find yourself dancing across from your best friend’s date, while your friend is dancing beside
your date. It’s fun to be part of such a casual group, but it’s also nice to go back to your own
date for the next slow song.
Later in the evening, you are warm and thirsty, so you head out into the hallway, where
there is punch to drink. Your date stays behind, fast-dancing as part of a large group. When you
return a few minutes later, the music has changed, and you can’t find your date anywhere.
Then you spot your date, across the dance floor, slow-dancing with someone else! You feel
confused, angry and foolish standing alone on the dance floor, so you hurry back out into the
hall. When your date comes looking for you a few songs later, you tell your date what you saw
and how you felt. The conversation turns into an argument, with heated emotions and raised
voices. You and your date decide that perhaps you had different ideas about the evening and
you break up.
A few weeks later, you’re walking out of school, when you see ahead of you the most
attractive person you’ve spotted in a long while…
Ask the students what the story had to do with chemistry. The students should be able to
identify the parts of the story that represent the five classes of chemical reactions.
Synthesis: two students joining as a couple
Double replacement: dancing with the other couple
Single replacement: your date dancing with someone else
Combustion: the argument
Decomposition: breaking up
Discuss with students the ways in which the analogy works and the ways it doesn’t. (Example
of a flaw—combustion releases energy, just as the argument was heated, but the argument
doesn’t have an outside reactant to represent oxygen.)
Direct the students to individually write a story that contains analogies for all five types of
fundamental chemical reactions. The story can be about whatever you want—a few ideas are
football games, telephone calls and cooking—except that you cannot copy any analogy you
heard in the class story. The story doesn’t need to be long—just long enough to include
comparisons to all five reaction types.
Homework
Complete your story, then highlight and identify the five (5) analogies for the five (5)
fundamental chemical reactions. Then write a sentence or two explaining the flaws/weaknesses
in your analogy—how is this story not a perfect comparison to real chemical reactions?
Modifications
 Advanced classes/students may complete the equation-sorting exercise quickly and
have time to begin working on the first day’s homework, the “Reaction Types
Worksheet,” in class.
 Students who need assistance organizing their thoughts while reading may benefit from
a worksheet with a blank table to organize their notes. A sample is provided at the end
of this lesson.
 Limited English Language students may need copies of the story to help improve
comprehension.
Assessment
Students’ understandings of the five types of reactions are assessed through:
 Observation and discussion of their classification schemes
 Correctly completed classifications of mathematical and chemical equations
 Solutions to “Reaction Types Worksheet”
 Analogy stories
Rubric for analogy story:
Reaction Type Analogy Story
_____ / 5 all reactions accurately are represented
_____ / 1 complete sentences
_____ / 2 grammar and spelling
_____ / 2 creativity and story flow
_____ / 10 total points
Classifying Chemical Reactions Worksheet
Name: ____________________________________ Period: _____
Classify each reaction as synthesis, decomposition, single replacement, double replacement or
combustion. The equations are not balanced.
1.
PbCl2 + AgNO3
Pb(NO3)2 + AgCl
2.
NH3 + HCl
3.
AlCl3 + Na2SO4
4.
Zn + S
5.
Al2(SO4)3 + BaCl2
6.
Al2S3
7.
H2SO4 + Fe
NH4Cl
___________________________
___________________________
Al2(SO4)3 + NaCl
ZnS
___________________________
___________________________
BaSO4 + AlCl3
Al + S
___________________________
___________________________
H2 + FeSO4
___________________________
8.
C12H22O11 + O2
CO2 + H2O
___________________________
9.
Mg(OH)2 + H2SO4
MgSO4 + H2O
___________________________
10.
NaOH +
Na2SO4 + Cu(OH)2
___________________________
11.
C4H12 + O2
12.
Fe + O2
13.
Mg3(PO4)2 + H2
14.
NH4NO3
15.
Cl2 + KBr
CuSO4
H2O + CO2
Fe2O3
___________________________
___________________________
Mg + H3PO4
___________________________
N2O + H2O
___________________________
KCl + Br2
___________________________
Classifying Chemical Reactions
Reading Notes—Section 10.2 (pages 284-291)
Reaction Type
Synthesis
Decomposition
Single Replacement
Double Replacement
Combustion
Sample Equation
Clues for Recognizing
Reaction Type
Teacher Notes:
Synthesis—two reactants join to form one product **clue: one product
A + B  AB
2 Na + Cl2  2 NaCl
Decomposition—one reactant breaks into several products **clue: one reactant
CD  C + D
2 H2O  2 H2 + O2
Single Replacement—an element in a compound switches places with a lone element **clue:
lonely element on each side
A + BC  AC + B
2 KBr + Cl2  2 KCl + Br2
Double Replacement—two compounds swap their positive and negative parts **clue: two
compounds on each side
AB + CD  AD + CB
AgNO3 + NaCl  AgCl + NaNO3
Combustion—an energy-releasing reaction with oxygen to produce one or more oxides
**Clue: O2 is a reactant, products are compounds with oxygen in them
AB + O2  AO + BO
C + O2  CO2
Mathematical Equations Challenge
Names of Group Members: __________________________
________________________
Challenge Question:
The mathematics professors have generally agreed that there are five (5) different possible
types of “addition” expressions. Using your observations skills, I am sure that you will
recognize similarities and subtle differences in each of the 21 mathematical equations. Can
you classify each of these mathematical equations into the correct five different categories?
Hints:
 Use scissors to cut out each equation from the accompanying sheet.
 No mathematics textbooks or calculators can be used at any time.
Report:
In the space below, your group’s reaction classification scheme should contain:
 a general description of each category
 two sample equations for each category
Classification Scheme:
Mathematical Equations Challenge
1.
28
+
54
=
82
2.
22
+
55
=
25
+
52
3.
40
+
22
=
44
+
18
4.
75
+
12
=
15
+
72
5.
131
=
44
+
18
+
69
6.
14
+
6
=
16
+
4
7.
45
+
2
=
42
+
5
8.
79
=
52
+
27
9.
20
+
58
+
16
=
94
10.
17
+
42
=
12
+
47
11.
33
+
29
=
44
+
18
12.
71
+
3
=
73
+
1
13.
62
+
49
=
111
14.
46
=
18
+
15
+
13
15.
12
+
50
=
18
+
44
16.
35
+
20
+
52
=
107
17.
59
+
48
=
49
+
58
18.
38
+
24
=
18
+
44
19.
67
+
1
=
61
+
7
20.
36
+
13
=
33
+
16
21.
48
+
14
=
44
+
18
Chemical Equations Challenge
Names of Group Members: _________________________
________________________
Challenge Question:
Can you classify each of these chemical reactions into five different categories?
Hints:
 Use scissors to cut out each reaction from the accompanying sheet.
 Do NOT balance the equations as this may confuse you.
 No textbooks can be used at any time.
Report:
In the space below, your group’s reaction classification scheme should contain:
 a general description of each category
 two sample equations for each category
Classification Scheme:
Chemical Equations Challenge
1.
SiO2
+
Mg
Si
2.
SO2
+
O2
SO3
3.
CaCl2 +
K3PO4
4.
CO
O2
5.
H2CO3
6.
CaCO3
+
HCl
H2CO3
+
CaCl2
7.
C4H10
+
O2
H20
+
CO2
8.
P4O10
+
H2O
H3PO4
9.
Cu
10.
NCl3
11.
Ag2SO4
12.
NaHCO3
13.
Li
14.
H2SO4
15.
BaO
16.
C10H22
17.
Al2(SO4)3
+
18.
CuBr
+
Br2
19.
CH4
+
O2
+
N2
+
Cu(NO3)2
(NH4)2SO4
+
H20
+
+
+
Hg
Cl2
NH4I
Na2CO3
LiOH
Ca
+
KCl
H2O
+
CO2
+
+
CO2
HgNO3
+
MgO
Ca3(PO4)2
CO2
+
+
HNO3
O2
+
+
H2O
+
H2
CaSO4
+
Ba(NO3)2
CO2
Ca(OH)2
+
AgI
H2
+
H2O
Al(OH)3
CuBr2
CO2
+
H2O
H2O
+
CaSO4
Instructor's Notes
Chemical Equations Challenge
Frustration with the Traditional Lecture Approach
During my first year of teaching I taught this material in a traditional lecture approach, and I
was very disappointed at the number of students who were not able to classify these
chemical reactions despite having been exposed to my "brilliant" lecture. I felt that my
organized, carefully scripted lesson should -have been an automatic success. How could they
not see things exactly as they had been told, exactly as their own notes told them?
I decided to take a chance during my second year of teaching. Would they be able to see the
patterns and trends in these chemical equations before I assigned the formal terms
synthesis, decomposition, single replacement, double replacement and combustion? I was
nervous at first but was absolutely stunned at how easily my students were able to do this. I
have experienced success with this in every class (regular or honors), and I am now a firm
believer in the constructivist belief of "experience it first, name it afterwards."
I am extremely proud of creating this activity because I enjoy teaching the types of reactions
after this activity. To see them nodding along with me as the formal names are introduced to
them, and hearing comments like "We saw that one!" is much more pleasant than hearing the
usual "How did you know it was a single replacement reaction again?"
Groups and Incentives to Finish Early
This cooperative activity takes about 30-50 minutes to make sure that everyone gets
finished. I score this as 10 points, and award the extra credit to the first three groups to
finish. Three extra points for being first, two points for the second group, one extra for being
third. This keeps the groups focused and minimizes the chances of groups merging.
Teacher's Role in the Classroom
Once the groups have been assigned and students understand the task, the teacher becomes
the facilitator. The teacher can walk around the classroom to monitor the students'
progress. Teachers should remain silent because students will often seek assistance through a
teacher's facial cues, comments, etc. To keep the groups on track, a teacher cannot simply let
the students go without some timely encouragement. I often make the following comments to
maintain a productive classroom atmosphere:
"We are looking for patterns and trends.'
"What do you start with? What do you end with?'
"Think about it... with only five different groups, they can't be too element specific."
"Is this right?"
"Well, explain to me why you put these together." Student justifies the categories... "Ok, I like
this one and that one, but I don't like this group here." THEN WALK AWAY.
"There seems to be one equation that just doesn't fit in this group." THEN WALK AWAY.
Two extensions for groups who finish early?
If a group finishes earlier than the rest, ask them to look closely at the double replacement
category. If they truly see the patterns, they should be able to predict the products of the
reactions. I will then give them both starting materials of a double replacement reaction.
"Give me the products and then I will believe you really see what I see."
Another extension is for students to write the formal names of the types of chemical
equations on the chalkboard. Ask the students to try to match the formal name with their five
different categories, "Don't be surprised if your students get all five correct in their first try!!!
Shocking, but true!!!
Why aren't the equations balanced?
The equations provided are not balanced and students are specifically told not to balance
them. This helps to mini-mire the potential for distraction since the coefficients do not
influence the classification of the chemical equations. Teachers who feel obligated to have the
equations balanced can ask students to do this after completing the activity.
Recommended Classification Scheme:
There are many different ways to categorize chemical reactions, but the equations were
specifically selected with the classification scheme described in a popular chemistry textbook.1
Synthesis: A chemical reaction with only 1 product.
SO2 +
O2
SO3
Decomposition: A chemical reaction with only 1 reactant.
H2CO3
CO2 + H2O
Single Replacement: An element and compound produce a new element and new
compound.
H2SO4 +
Ca
CaSO4 + H2
Double Replacement: Two compounds react by exchanging ions producing two new
compounds.
NaCl + AgNO 3
AgCl + NaNO 3
Combustion: A hydrocarbon and oxygen react to produce carbon dioxide
and water.
CH4 + O2
CO2 + H2O
R. C.; Smith, R G.; Price, J. Merrill Chemistry, 1995, Glencoe/McGraw-Hill, p. 228-230.
Flinn Scientific Foundation
Chemical Equations Simulation for Teachers
Synthesis (Only one number on the right side)
35
+
20
+
52
=
28
+
54
=
82
62
+
49
=
111
107
Decomposition (Start with one number and end with many)
46
=
18
+
15
79
=
52
+
27
131
=
44
+
18
+
13
+
69
Double Replacement (Switch ones' positions to form two new numbers)
17
+
42
=
12
+
47
22
+
55
=
25
+
52
59
+
48
=
49
+
58
Single Replacement (Single digit replaces one's position)
45
+
2
=
42
+
5
67
+
1
=
61
+
7
14
+
6
=
16
+
4
right
side
Combustion
(Numbers
on
the
40
+
22
=
44
+
18
12
+
50
=
18
+
44
33
+
29
=
44
+
18
Flinn Scientific Foundation
are
always
18
and
44)