Density Detective: Mass, Volume and Kinds of Matter

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Science · Chemistry
SP-CHEM-002 · Free to print and use in your classroom · substituteplans.com
Page 2
Density Detective: Mass, Volume and Kinds of
Matter
Science · Chemistry · Grades 9-10 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). No other prep is needed.
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 (optional)
Goal for today: Students will classify samples of matter and use the formula density = mass ÷ volume to identify
materials and predict whether they float.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Write on the board: density = mass ÷ volume. Also write: 1 cm³ = 1 mL.
☐ Keep the answer key on your desk. No science knowledge is needed; there are no labs or materials today.
Say this to start
Good morning! Today in chemistry you will act as detectives. First you will sort different kinds of matter. Then you will
use a simple formula, density equals mass divided by volume, to figure out what an unknown metal is. It is all paper
and calculator work. Everything you need is on the worksheet.

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Science · Chemistry
SP-CHEM-002 · Free to print and use in your classroom · substituteplans.com
Page 3
Run of show
Minutes
What you do
What students do
0–5
Take attendance. Hand out the worksheet and ask
students to read the definitions box.
Read the definitions and the density table.
5–12
Read the worked example aloud: a sample has mass 20.0 g
and volume 10.0 cm³. Density = 20.0 ÷ 10.0 = 2.00 g/cm³.
Explain that a bigger number means the material is packed
more tightly.
Follow along and write the example in the
margin.
12–22
Tell students to complete the sorting table in Part A (no
numbers, just classification). Partners may compare.
Write element, compound, homogeneous
mixture or heterogeneous mixture for each
sample.
22–40
Tell students to work on questions 1–6 (density problems).
Walk around. If students are stuck, ask: What is the mass?
What is the volume? Which one goes on top?
Solve each problem in the work box with
units, then circle the answer.
40–47
Have students complete questions 7 and 8, then read the
answers aloud from the key.
Answer the float-or-sink questions and
check their work.
47–50
Collect the worksheets and put them in a stack for the
teacher.
Hand in the worksheet.
If things go wrong
• If students ask what a heterogeneous mixture is, point to the definitions box: you can see the different parts.
• If a student gets a very different answer, check that they divided mass by volume and not the other way
around.
• If students ask whether to round, tell them to give 3 significant figures unless the worksheet says otherwise.
• If the class finishes early, use the early finisher list.
Early finishers
• Write your own density problem for a classmate: pick a metal from the table, a volume, and ask for the mass.
Solve it on the back.
• Explain in two sentences why a huge ship made of steel can float.
Support and challenge
• Support: Complete the sorting table and questions 1, 2, 3 and 7. Use the worked example as a model.
• Challenge: A gold bar has a volume of 125 cm³. Find its mass using the table. Show your steps on the back.

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Science · Chemistry
SP-CHEM-002 · Free to print and use in your classroom · substituteplans.com
Page 4
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: