The Mole: Molar Mass and Conversions

SubstitutePlans.com
Science · Chemistry
SP-CHEM-008 · Free to print and use in your classroom · substituteplans.com
Page 2
The Mole: Molar Mass and Conversions
Science · Chemistry · Grades 10-11 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). Write the conversion map 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, Calculators (strongly recommended), Whiteboard or chalkboard
Goal for today: Students will calculate molar masses from atomic masses and convert between grams, moles and
particles.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Write on the board: grams ÷ molar mass = moles; moles × molar mass = grams; moles × 6.022 × 10²³ =
particles.
☐ Keep the answer key on your desk. Students need a calculator; spares help.
Say this to start
Good morning! Today in chemistry you will work with the mole, which is just a counting unit like a dozen, but much
bigger. One mole is 6.022 × 10²³ particles. You will find molar masses and then convert between grams, moles and
particles. All the atomic masses you need are printed on the worksheet.
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 and the list of atomic masses.
5–13
Read this example aloud: molar mass of H₂O = 2(1.008) +
15.999 = 18.015 g/mol. Then: 36.0 g of water is 36.0 ÷
18.015 = 2.00 mol.
Follow along and copy the example.
13–25
Tell students to complete questions 1–4 (molar masses).
Remind them to multiply each atomic mass by the number
of atoms.
Calculate each molar mass and write the
units.
25–42
Tell students to complete questions 5–10 (conversions).
Walk around and ask, “What units do you have? What units
do you want?”
Convert and show work in the boxes.
42–47
Have students answer questions 11 and 12, then read the
answers aloud from the key.
Answer the two multiple-choice questions
and check their work.
47–50
Collect the worksheets and put them in a stack for the
teacher.
Hand in the worksheet.

SubstitutePlans.com
Science · Chemistry
SP-CHEM-008 · Free to print and use in your classroom · substituteplans.com
Page 3
If things go wrong
• If students get answers that are far off, check whether they multiplied or divided. Grams to moles divides by
molar mass.
• If students ask how many digits to keep, tell them to give 3 significant figures.
• If students have no calculator, they can leave answers in expression form (for example 36.0 ÷ 18.015) and
still earn credit.
• If the class finishes early, use the early finisher list.
Early finishers
• Find the molar mass of NaCl and use it to find the mass of 2.00 mol on the back.
• Explain in two sentences why a mole of water has more mass than a mole of hydrogen gas.
Support and challenge
• Support: Complete questions 1, 2, 5 and 6. The first conversion follows the worked example.
• Challenge: How many oxygen atoms are in 0.500 mol of CO₂? Show every step on the back.
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:
Anything the teacher should know: