STEM Lesson #5 – Density – Rainbow Straws Lab
Concept/ Main Idea:
This lesson is an inquiry based lesson on density
Introduction/ Main question/ Lead-in:
Students will be presented with the “Floating logs” probe to begin this lesson. The teacher could also
begin by posing the question “Why do things float?”
Standards Addressed:
Ohio College and Career Readiness Standards: Science: Grade 9 – Properties of Matter
Learning Goal:
Students will understand there are many different ways to categorize matter based on physical and chemical
properties
Critical Vocabulary:
Volume, Mass, Density
Materials and Equipment:
Clear straws, Modeling clay, 4 liquids of different density (water, alcohol, olive oil, corn oil)
Safety and Disposal:
Students should wear safety goggle when working with liquids.
Teacher Information:
Background Information
Density is a measure of how much matter is contained in a certain volume of a substance. A substance
that has low density is “light” in comparison with something else of the same volume. Balloons float because
they are less dense than the air around them. A substance that has a high density is “heavy” in comparison
with another object of the same volume. A stone sinks to the bottom of a pond because the stone is more
dense than the water around it.
You can compare the density of two objects of the same volume by holding one in each hand. The
lighter one is less dense; the heavier one is more dense. If you held a brick in one had and a sponge of the
same size in the other, you would know instantly that the brick is more dense than the sponge. Remember
that weight and density are different. Two pounds of feathers are heavier than one pound of steal. But the
feathers are less dense than the steel, so two pounds of feathers have a greater volume than one pound of
steel.
Density determines whether an object will float or sink. An object will float when placed in water if it is
less dense than water. If an object is more dense than water, the object will sink.
The density of an object is calculated by dividing the object’s mass by its volume. Remember on earth
to determine an objects mass we weight it.
Density = Mass
Volume
Lesson Procedures
Day 1 – Pre-assessment and content introduction
1. Students will be presented with the “Floating logs” probe to begin this lesson. The teacher
could also begin by posing the question “Why do things float?” Students will complete the
probe on their own and then discuss their response with their neighbor. The teacher will
survey the overall class response using a Posterboard with columns labeled A, B, C. Students
will place a post it note in the column they chose for their response. (or the teacher could use
clickers to quickly survey the class and post responses on the smart board)
2. The teacher will introduce the concept of density and students will take notes.
3. Students will practice finding the density of 5 objects using the activity “Density matters”
Day 2 – Rainbow Straws Lab
1. The teacher will review the concept of density. The discussion should focus on what happens
when materials of different density are put together. The teacher will explain that the students
2. Students will complete the Rainbow Straws Lab.
3. For homework and a formative assessment students will complete the More Density Practice
worksheet.
4. As an exit slip students will complete the “Comparing cubes” probe.
Pre-activity Discussion:
Students will be presented with the “Floating logs” probe to begin this lesson. The teacher could also
begin by posing the question “Why do things float?”
Student version of activity:
See Rainbow Straws worksheets
Post-activity Discussion:
See the “Comparing Cubes” Probe
Real world Applications and extensions:
This lesson was created for a 9th grade Physical Science class. For a more advanced class I would
not give notes on density instead I would have the students do a lab to find the relationship between
mass and volume
Differentiated Instruction:
This lesson was created for a 9th grade Physical Science class. For a more advanced class I would
not give notes on density instead I would have the students do a lab to find the relationship between
mass and volume
Assessments (formative, authentic, and summative):
Pre-assessment – “Floating Logs” Probe
Formative assessment – Density Matters lab
Formative assessment – Rainbow Straws lab
Formative assessment – More Density Practice
Post assessment – “Comparing Cubes” Probe
Summative - See Matter Pop-up Book
Citations:
Addison, P. (2004) Rainbow Straws. Miami University Course Manual.
Keeley, P. (2007). Comparing Cubes & Floating Logs. Uncovering Student Ideas in Science: Volume
2. .19-25 & 27-32.