Science Lesson Kit · Teacher Resource
Density: Mass, Volume & Floating — 5E Lesson Plan
Physical Science · 55 minutes
Grade 6
5E lesson flow
01
Engage
7 min
Teacher Does
Show a large wood block and small metal bolt and compare their masses and floating behavior.
Students Do
Predict which is denser and explain initial reasoning.
Ask
- Why is mass alone not enough?
Look For
Need to compare mass with volume.
02
Explore
15 min
Teacher Does
Guide mass and volume measurements for regular and irregular objects.
Students Do
Measure, calculate density, and record units.
Ask
- How will you measure volume for this object?
Look For
Dimensions or displacement chosen appropriately.
03
Explain
10 min
Teacher Does
Formalize density as mass/volume and connect density comparison with water.
Students Do
Compare same-mass and same-volume examples.
Ask
- What happens to density if mass stays the same while volume increases?
Look For
Density decreases.
04
Elaborate
15 min
Teacher Does
Run sink/float tests and introduce buoyant force versus weight diagrams.
Students Do
Predict, test, and explain observed motion using density and net force.
Ask
- What force pattern fits an object rising, floating, or sinking?
Look For
Upward net force, balanced vertical forces, or downward net force.
05
Evaluate
8 min
Teacher Does
Assign the density evidence challenge.
Students Do
Calculate, predict, compare with evidence, and explain one mismatch or limitation.
Ask
- Which evidence supports your prediction and which evidence tests it?
Look For
Correct ratio, units, and force reasoning.
Student goal
I can calculate density and use density plus force evidence to explain floating and sinking.
Learning objectives
- Calculate density from mass and volume and interpret density as a ratio rather than as mass alone.
- Use consistent measurements to compare the densities of regular and irregular objects.
- Use density comparison and vertical-force reasoning to explain sinking and floating in water.
Materials
- Digital balances
- Graduated cylinders
- Water tubs
- Regular and irregular objects
- Rulers
- Density tables
Before class
- Choose objects with clean, interpretable sink/float behavior.
- Prepare one hollow-object example.
- Premeasure reference values so major student measurement errors can be recognized.
- Mark safe water levels and towel stations.
Prior knowledge
- Students can divide whole numbers and decimals with support.
- Students know mass and volume are different measurable properties.
- Students have prior experience with balanced and unbalanced forces.
Vocabulary
- density
- The ratio of an object's mass to its volume.
- mass
- A measure of the amount of matter in an object.
- volume
- The amount of space an object or substance occupies.
- displacement
- A method of finding volume by measuring how much liquid level changes when an object is submerged.
- buoyant force
- The upward force a fluid exerts on an object in the fluid.
- weight
- The downward gravitational force on an object.
- net force
- The combined effect of all forces acting on an object.
- neutral buoyancy
- A condition in which upward and downward forces balance so an object remains suspended rather than rising or sinking.
Differentiation
- Provide a density formula triangle only after students understand the ratio concept.
- Use same-mass and same-volume physical comparisons.
- Allow calculators for arithmetic so assessment can focus on scientific reasoning.
- For extension, ask students to design a clay shape that floats without changing the clay's mass and explain the average-density change.
Assessment
- Check density calculations and units.
- Check measurement method selection.
- Check density-based predictions against test evidence.
- Require a force-balance explanation for at least one floating or sinking case.
Exit ticket
A 90 g object has volume 120 mL. Calculate its density and predict whether it is likely to float in water.
Extension
Keep the mass of a clay sample constant while changing its shape to make it float, then explain the change in overall volume, average density, and displaced water.