SME
Grade 6 Science · Problem type
Volume by water displacement
Use this for “The water rose from 50 mL to 62 mL. What is the object’s volume and density?”
Diagram
The water rose from 50 mL to 62 mL: the object takes up 12 cm³.
Mass: 32.4 g
Density: 2.70 g/cm³
This is an example. Type your own values to start a new problem.
Water level before
example
Water level after
example
Object volume
calculated
Mass
example
Density
calculated · g/cm³
Formulas
62 − 50 = 12
Water level after − water level before = object volume
32.4 ÷ 12 = 2.70
Mass ÷ object volume = density
Assumptions
•
The water rises by exactly the object’s volume when it sinks all the way under.
•
1 mL of space is 1 cm³, so the rise in mL is the volume in cm³.
•
Read the level at the bottom of the curved surface, with your eye level with it.
•
For an object that floats, push it under with a thin wire.
Step-by-step
WE KNOW
Water level before: 50 mL
Water level after: 62 mL
Mass: 32.4 g
FIND
object volume, density
Step 1 · Find object volume
62 − 50 = ?
Water level after − water level before = object volume
The object pushes aside its own volume of water, so the rise in mL is its volume in cm³ (1 mL = 1 cm³).
Object volume = 12 cm³
Step 2 · Find density
32.4 ÷ 12 = ?
Mass ÷ object volume = density
Share the mass over the cubic centimeters of the object.
Density = 2.70 g/cm³ (about the density of aluminum: it sinks in water)
Check
Put the numbers back in. Both sides should match.
62 − 50 = 12 ✓
12 × 2.70 = 32.4 ✓
Topic check
See what you know: 5 questions on this topic
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