Balancing Chemical Equations: Count, Adjust, Check

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Science · Chemistry
SP-CHEM-007 · Free to print and use in your classroom · substituteplans.com
Page 2
Balancing Chemical Equations: Count, Adjust,
Check
Science · Chemistry · Grades 9-11 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). Write the three balancing rules on the board.
Technology
None. A basic calculator is optional.
Student
independence
High. Students work alone, then check with a partner.
Copies to make
One 2-page worksheet per student
Materials
Pencils, Worksheet
Goal for today: Students will balance chemical equations by adjusting coefficients and verify the balance by counting
atoms on both sides.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Write on the board: 1) Count atoms on each side. 2) Change only the big numbers in front (coefficients). 3)
Never change the small subscripts. 4) Recount.
☐ Keep the answer key on your desk. You do not need any chemistry knowledge; students check by counting.
Say this to start
Good morning! Today in chemistry you will balance chemical equations. A chemical reaction never creates or destroys
atoms, so each side of the arrow must have the same number of each atom. Your job is to put numbers in front of the
formulas until the counts match. The board shows the rules. This is paper work only.

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Science · Chemistry
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Page 3
Run of show
Minutes
What you do
What students do
0–5
Take attendance. Hand out the worksheet. Ask students to
read the Key Ideas box.
Read the box silently.
5–13
Read this example aloud: H₂ + O₂ → H₂O. Left: 2 H, 2 O.
Right: 2 H, 1 O. Put 2 in front of H₂O: now 4 H and 2 O on
the right. Put 2 in front of H₂: now 4 H on the left. Both
sides have 4 H and 2 O. Balanced: 2H₂ + O₂ → 2H₂O.
Follow along and copy the example.
13–32
Tell students to complete questions 1–8. Write 1 if no
coefficient is needed. Walk around and ask, “Which atom is
unbalanced right now?”
Balance each equation and count atoms to
check.
32–42
Tell students to complete the atom-counting table, then
answer questions 9–12.
Count atoms in the table and answer the
true/false and multiple-choice questions.
42–47
Read the answers aloud from the key. Students check and
correct their work.
Check answers and fix mistakes.
47–50
Collect the worksheets and put them in a stack for the
teacher.
Hand in the worksheet.
If things go wrong
• If students get stuck, tell them to start with an atom that appears in only one formula on each side, and to
leave hydrogen and oxygen for the end.
• If students want to change a subscript, remind them that changing a subscript changes the substance. Only
coefficients may be changed.
• If students get fractions, tell them to multiply everything by 2 to get whole numbers.
• If a student finishes early, use the early finisher list.
Early finishers
• Pick one balanced equation and draw circles to show the atoms on each side. Show that the counts match.
• Write a two-sentence explanation of why balancing equations matters for conservation of mass.
Support and challenge
• Support: Complete questions 1, 2, 3, 5 and 6 and the table. The first answer is shown in the board example.
• Challenge: Balance this equation on the back: Fe₂O₃ + CO → Fe + CO₂.
Notes for the teacher (you fill this in)
Jot a few lines before you leave. A full Daily Sub Report is in the free Sub Survival Kit at SubstitutePlans.com.
How far the class got / what to pick up next:
Students who were especially helpful:

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Anything the teacher should know: