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Packing mass into volume

Science · Matter & Materials · ages 15-16

Name ______________________ Date ____________

Which set of units fits density?
- Joules per kilogram per degree
- Newtons per square centimetre
- Kilograms per cubic metre
How do you calculate density?
- Mass divided by volume
- Volume divided by mass
- Mass multiplied by volume
Two lumps can have the same mass but different densities.
Circle one: True False
A block has density 4 g/cm3 and volume 50 cm3. A second block has the same mass and density 10 g/cm3. What is the second block's volume in cm3?
Answer: ______________
A stone has mass 300 g. Full immersion without trapped bubbles raises a cylinder reading from 80 cm3 to 180 cm3. It does not dissolve, react with water or absorb it. What is its density?
- 3 g per cubic centimetre
- 30 g per cubic centimetre
- 300 g per cubic centimetre
An object displaces the same volume when submerged in fresh water and in denser seawater. Which comparison of upthrust is correct?
- Fresh water gives greater upthrust because the object gains mass there
- Both give equal upthrust because only the object's own mass matters
- Seawater gives greater upthrust because the displaced fluid weighs more
Air is sealed in a syringe with a movable plunger. Warming increases its volume and no air leaks out. What happens to its density?
- It rises
- It falls
- It stays the same
A student says any gas with fast-moving particles must have high density. Which reply explains the mistake?
- Fast particles have no mass, so the gas sample must have zero density
- Density depends on mass per volume, not particle speed alone
- Every gas has the same density because its particles can move freely

Answer key

For grown-ups. Fold this page away before handing over the rest.

Packing mass into volume W1-mt_HrKI1-UzfI-s1

Kilograms per cubic metre · Kilograms measure mass and cubic metres measure volume. Density units are mass units divided by volume units.
Mass divided by volume · Density is the mass in each unit of volume, so divide mass by volume.
True · At equal mass, different volumes give different mass-per-volume values.
20 · The shared mass is 4 × 50 = 200 g. The second block's volume is mass / density = 200 / 10 = 20 cm3.
3 g per cubic centimetre · The stone's volume is 180 - 80 = 100 cm3. Its density is 300 / 100 = 3 g/cm3.
Seawater gives greater upthrust because the displaced fluid weighs more · Upthrust equals the weight of displaced fluid. Equal volumes of denser seawater have greater mass and weight.
It falls · No air escapes, so mass stays the same. Dividing that mass by a larger volume gives a lower density.
Density depends on mass per volume, not particle speed alone · Fast motion alone does not tell you the mass per volume. Particle spacing helps explain why gases are usually much less dense than liquids and solids.