Balancing Reactions – DID Unit
This unit covers the topic of balancing chemical reactions in a regular chemistry level course in
a high school setting. The unit is created using the Dynamic Instructional Design model or DID. The
lesson plans follow Gagne’s nine events of instruction model.
This topic will be taught to a majority of 10th graders with a few 11th and possibly 12th graders
mixed in. The class will be made up of students from many different backgrounds and cultures: White,
Hispanic, Indian, Asian, and African-American, in order of decreasing class percentage. The
languages spoken throughout the class will vary as well. Close to half of the class will have English as
their second language, but they all will be fluent and speak English during the lessons. Chemistry,
especially balancing reactions, relies heavily on a student’s math ability. Students will need a firm
understanding of Algebra 1 and be able to do basic arithmetic quickly. All students will have taken
Algebra 1. Older students, 11th and 12th graders, will have taken more math and generally can handle
the math concepts better than the 10th graders. Since the grade, cultural, and math backgrounds will
differ among the students, their learning styles and trends will vary as well. Students will need to see
many problems modeled with a chance to ask many questions. Students will also benefit from the
different ways these problems will be presented to them. There will also be students with IEP’s and
specific learning plans in the class. A few groups will have a cooperating teacher in the room for their
needs.
At the conclusion of the unit, students will be able to balance a chemical reaction without
polyatomic ions through basic arithmetic with 90% accuracy. Students will be able to balance a
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Balancing Reactions – DID Unit
chemical equation with polyatomic ions through basic arithmetic with 80% accuracy. Students will
also be able to explain why a reaction needs to be balanced in a short essay with 100% accuracy.
These goals along with their activities are aligned with Illinois State Standards for science. Standard
11.A.4a for formulating hypotheses, standard 11.A.4b for conducting simulations to test hypotheses,
and standard 12.C.4b for the explanation of atomic structure are all represented in this unit.
The classroom is a large science room that has an instructional section with chalkboards and
student desks along with a lab section in the back, with large lab tables and sinks. The desks are
arranged so that they face the front chalkboard for any large group discussion or instruction. There is
also a projector and screen for any instruction that requires a computer or overhead. Along one side is
a large demonstration table for the instructor to perform chemical demonstrations. Along the other
side of the room are various models and interactive demos that students can read about and discover if
they have a spare moment. Classroom student computers are not available so for any computer work
the class will need to reserve and move to one of our computer labs. For any lab work done with
chemicals, students work in the back at their assigned lab station in their assigned lab groups.
Depending on the size of the class, groups will contain 2-3 students. Every day when students come
into class, there will be a question up on the board that they will be expected to write down on a given
sheet of paper and respond to. These questions will have to do with our unit and get students thinking
about the topic and asking questions about what they are going to do or learn.
The teaching and learning that will take place will follow Gagne’s model of instructional
design. This model uses nine events of instruction to promote learning: gain attention, describe the
goals, stimulate recall knowledge, present knew content, provide guidance, elicit performance, provide
feedback, assess, and enhance retention. This unit will follow these events over the 5 days of lessons.
Day 1 will consist of the students performing a lab experiment in the back of the classroom and
making some observations of their results. They will perform a reaction in a sealed bottle. They will
take the mass before the reaction and after the reaction. Students will see that the mass remains
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Balancing Reactions – DID Unit
unchanged even though what was in the bottle initially has changed. They will record this data and
conclusion in their lab books and we will discuss their results after their experiment. This discussion is
an important step because students need to know what significant means in terms of their results. They
will argue that a change has occurred if their initial mass was 42.1g and their final mass was 41.9g, but
is the change significant? At the conclusion of this day we will list the goals of this unit and connect
them with the results of our experiment. This day follows Gagne’s steps 1 and 2.
Day 2 will be used to model what is happening molecularly when we balance a reaction.
Students will have guided notes that we will use along with a slideshow presentation. They will be
seated in their seats. A computer and projector will be used. Students will draw pictures of molecules,
alter coefficients, and see how that effects how many molecules and atoms there are in a reaction. At
the end, students will be given 10 minutes to balance 4 reactions that we will go over once they are
done. This day follows Gagne’s steps 3, 4 and 5. Students need to recall what atoms and molecules
are and the parts to a reaction. They are presented with new information and shown how to properly
use this information.
Day 3 will focus on practice. Students will be given 12 reactions to balance of increasing
difficulty. They will also be provided with flashcards. The cards contain the chemical formulas and
numbers for the students to “build” the reaction and then balance it using the cards. When balancing,
students tend to want to change numbers that they are not allowed to change. Also, many reactions
require numbers to be changed multiple times as a student works through the problem and they have to
erase frequently. The use of the flashcards eliminates these two big problem areas. Students cannot
change what is on the card. The cards also make it easy to switch numbers without erasing. Students
that need something more hands-on will want to use the cards. They provide another way to see and
manipulate the problem. Keep in mind “educational technology includes any media that can be used in
instruction” (Lever-Duffy & McDonald, 2011, p.5), not just computers or digital devices. Students
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Balancing Reactions – DID Unit
that show a quick understanding on how to balance may not want to use the cards. Students will work
in their lab groups in the lab area of the class. This day follows Gagne’s step 6.
Day 4 will take place in a computer lab. Students will be using the interactive simulation for
balancing reactions provided by the University of Colorado at Boulder website. They will be provided
with instructions and a place to record their answers. This simulation brings together the previous two
days of instruction. Students get to see the molecules in the reaction and be able to quickly change
numbers to see how they affect the reaction. The simulation has multiple forms of feedback for
students to use including bar graphs and a balance beam. This day includes Gagne’s steps 6, 7, and 8.
The simulation provides more time for practice and provides immediate feedback. As a student works
through a problem they can see themselves getting closer to having a balanced reaction until they get it
right. The last part of the simulation takes students through a drill of increasing difficulty. Students
will have to score a certain number right before moving on to the hard difficulties.
Day 5 will consist of a summative assessment in the form of a quiz. The quiz will consist of
reactions that need to be balanced. Students will also have to explain why reactions need to be
balanced. This quiz will serve as an indication on how well and how much time it takes for students to
balance reactions. If a student does not receive at least a 70%, they will be given the option of retaking
a different quiz after they have received some form of remediation. Throughout the week, if a student
has shown that they require more time to balance reactions, they will be given a smaller quiz designed
to be completed in the amount of time they have for the class. More time can be given if a class period
is not enough.
To administer this unit various technologies and materials will be needed. A computer with a
projector and slideshow software will be needed by the teacher for the day 2 instruction. By using the
slideshow, you can quickly show pictures of the various molecules being discussed. You will not have
to draw them by hand. The students will also need a computer for day 4 using the simulation. The
simulation provides instant feedback for students and allows them to see how a reaction changes as
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Balancing Reactions – DID Unit
you balance it. It also allows them to quickly change their answers as they work through a problem. A
class set of flashcards will be used by groups on day 3. The flashcards provide focus for students and
keeps them from doing mistakes that they would normally do. It also helps them work as a group with
one set of large flashcards. For the lab portion, a digital balance, sealable bottle, test tube, and two
chemicals that form a reaction will be needed for each group on day 1. Good reactions are either
magnesium or zinc with dilute hydrochloric acid. The lab lets students discover and measure why we
need to balance reactions. By performing the lab themselves, they will remember that what they
started with is what they ended with. The handouts needed are lab instructions, guided notes, practice
worksheet, simulation directions, and the quiz.
A range of formative assessment will be collected leading up to their summative assessment.
One of the key components to this design is that “the instructional design must be flexible enough to
embrace and use data provided by ongoing feedback from learners.”(Lever-Duffy & McDonald, 2011,
p.52) Students will turn in their lab report, consisting of their hypothesis, data, and a conclusion to
what their data means. Our guided notes will be a time for informal questions and small practice. This
day is the first day to assess whether or not the class needs to see what is going on in a different
manner, such as model kits. The reaction they did in lab can also be redone as a demonstration by the
instructor to connect with the previous day. Their assignment for day 3 will be collected and graded.
This is the first chance to look at how the students perform on their own or in a small group. Another
day may be needed for practice for some students. Their drill with the simulation will also be
recorded. They might have to retry parts of the drill before moving on. It allows the teacher and
student to know how they are performing on various levels with balancing reactions. This is the last
planned day before their summative assessment. Their scores on the drill will be monitored and the
decision to include another day of practice can be made based on those scores. The quiz given will be
the last evaluation the students will perform during the unit. A separate evaluation will be given
relating back to our objectives form the beginning of the week. The questions will ask students if they
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Balancing Reactions – DID Unit
feel they have learned and accomplished the objectives we set out to do. It will also offer a chance for
feedback on the unit, what the students enjoyed, disliked, and what they would change. With all of
these forms of assessment, the instructor will have a clear view on how well the students can balance
reactions and what needs to be changed.
References
Illinois State Board of Education. (2012). Science standards [Data table]. Retrieved from
http://www.isbe.state.il.us/ils/science/standards.htm
Lever-Duffy, Judy, & McDonald, Jean B. (2011). Teaching and Learning with Technology (4th ed.).
Boston, MA: Pearson
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