Lesson Outline for Lesson #1 – Unit #9
Candidate: Olexandr Andriyashchenko
Date: 8 January, 2016
Lesson Part
Grade level: 11th - 12th AP CHEM 201 chemistry course
Class topic and central focus: balancing redox reactions by halfreaction method and their place in real world.
Activity description/Teacher does
Title
Balancing redox half-reactions.
Standard
NGSS: HS-PS1-7
Students do
Use mathematical representations to support the claim that atoms […] are conserved during a
chemical reaction.
Washington Science K-12 Standard: 9-11 PS2G
Chemical reactions change the arrangement of atoms in the molecules of substances
(Performance Expectations: Use a chemical equation to illustrate how the atoms in
molecules are arranged before and after a reaction).
EARL: #4
Central Focus (CF) Balancing redox reactions by half-reaction method and their place in real world.
Academic Language Half-reactions, dichromate, iodide, chromium (III+), iodine, oxygen, hydrogen, atoms, protons (H+),
hydroxide (OH-), electrons, charge, water, redox, reactions, reduction, reducing agent, oxidation,
oxidizing agent.
I can balance redox half-reactions that involve electron transfer.
Learning Target
(LT)
I can “use a chemical equation to illustrate how the atoms in
molecules are arranged before and after a reaction.” (Washington
K-12 standards)
Engage (video, review, thoughts), (~13 min.).
Asks students if they had any chances to do some non-school
related chemistry at home. (Engage).
Volunteer answers.
Shows the video of oxidation of glycerin by potassium
permanganate and states that we will focus on redox reactions.
(Engage).
https://www.youtube.com/watch?v=oZJnbSwjC0s
Watch the video.
Asks what students think about the video. Then reminds students
about the importance of safety and that science indeed could be
awesome.
Volunteer answers.
Instruction (e.g. States that today we begin our unit about redox reactions and that Listen.
inquiry, preview, the lesson will be about learning how to balance redox halfreview, etc.)
reactions. (Engage).
Asks students to read the lesson’s LT’s and standards.
Read.
Lists on the board the following list of terms: half-reaction, proton Turn to a neighbor and define the
(H+), hydroxide (OH-), redox, reduced, reducing agent, oxidized,
terms.
oxidizing agent, and asks students to turn to a neighbor and define
these together in their own words. (Engage-Explore).
Asks the class why do we care about these terms. (EngageExplore).
Volunteer answers.
Asks for definitions of terms. If they are wrong, asks student’s
peers what they think (if wrong, then rationale for correction)
Peers listen and “correct”
volunteers by thinking (orally).
about an answer thus indirectly “correcting” a volunteer. (EngageExplore).
Explore (balancing half-reaction), (~15 min.).
Invites students to think (brainstorm) of a method (algorithm) to
Brainstorm collaboratively.
balance the redox half-reaction collaboratively in groups of four for
10 min in the worksheet (#1). The example: Cr2O72-  Cr3+ (Explore).
Explore (watching and “salvaging”), (during Explore).
Circulates around the room and checks what everyone does.
Brainstorm collaboratively.
Listen to students’ ideas and answer questions being careful not to Ask questions if needed.
give out the actual method of balancing.
Informal

Assessment


If no one gets anywhere ask the class for ideas so far how to Share ideas.
balance.
Listen and interpret.
If no one provides a reasonable workable idea (most likely),
ask the class: “Have you considered using H20 for balancing?”
Invites for 5 more minutes of brainstorming collaboratively in
Brainstorm collaboratively.
groups on #1. (Explore).
Explain (walking over Cr2O72-  Cr3+ ), (~6-9 min.).
If at least someone “discovers” the balancing method for Cr2O72- 
Cr3+, make a note of that. Also check other tables for their partial
solutions and jot down what they have.
Ask different tables (groups of students) to share their partial
Share solutions and listen to
solutions (steps). Write only those that represent actual steps
peers.
(students might have similar steps, so they constitute only one step
at a time). Answers of student(s) who “discovered” the method will
complement partial solutions and together the whole class has
“discovered” the method. (Explain).
Practice Activity
or
Support
Complement the class for work.
But if no one “discovers”…
As above ask different tables (groups of students) to share their
Share solutions and listen to
partial solutions (steps). Write only those that represent actual
peers.
steps (students might have similar steps, so they constitute only
one step at a time). Add anything else (steps) to have a completed
method of balancing. (Explain).
Complement the class for work.
Ask the class to turn to a neighbor and explain to one another what Explain steps to a neighbor.
those steps for balancing mean. (Explain).
Explain (walking over Cr2O72-  Cr3+ ), (during Explain).
Informal Walk around the class and listen to students. Provide clarifications Explain steps to a neighbor.
Assessment if needed. (Explain).
Practice Activity
or
Support
Extend/Elaborate (balance AsO43-  AsO2- ), (~15).
State that now students should do problem #2 in worksheet on
their own collaboratively: AsO43-  AsO2- (Extend/Elaborate).
Evaluate/Reflect (reflection), (~5 min.).
Announce that the worksheet is due tomorrow.
Work collaboratively.
Listen.
Instruct students to complete Reflection section of the worksheet Students complete Reflection
individually in class and problems #3-6 and Homework section at
section and get a stamp.
home and bring worksheets next day. Students who completely (or
almost) answered problems (in class) get green stamp on their
handout, those who complete up to half of it get yellow stamp, and
those who did not attempt it get red stamp. This is done for future
grade on completeness of work. (Evaluate).
Closure
Assessment of
Reflection section:
Student Voice
1. What was confusing to me?
2. What was clear? What have I understood?
3. What did I learn from today’s lesson?
4. Rate yourself on your confidence of your understanding of
Learning Targets. Explain your self-rating.
Teacher circulates around the room 1-2 min. prior to the bell ring
and stamps students’ worksheets.
Students show teacher their
reflections and get stamps.
This lesson is for 55 minutes.
Assumptions: an instructor has taught concepts and students are familiar with these terms: half-reaction, proton (H+),
hydroxide (OH-), redox, reduced, reducing agent, oxidized, oxidizing agent.