Free density worksheet with answers for Grade 8: calculate density, find mass and volume, water displacement, sink or float and a density column.
By Kris Reddy, Ontario teacher · Updated October 17, 2026 · 22 questions (30 marks) · PDF + answer key
This free density worksheet gives Grade 8 students full practice with D = m/V. Students calculate density and use a reference table to identify four mystery substances, rearrange the formula to find mass and volume, and read drawn graduated cylinders to find the volume of a rock and a metal key by water displacement.
On the second page they predict whether objects sink or float in water, decide where four objects settle in a drawn density column of oil, water and honey, explain why ice and oil float and how a steel ship stays up, and correct the common "heavier means denser" mistake. Every answer was checked by computer. To print it, use the Download button above.
| Part | Skill practised | Marks |
|---|---|---|
| A | Calculate density and identify the substance | 8 |
| B | Find the mass or volume | 3 |
| C | Volume by displacement (drawn graduated cylinders) | 4 |
| D | Sink or float? | 4 |
| E | The density column | 3 |
| F | Explain your thinking | 6 |
| G | Spot the mistake | 2 |
The density worksheet supports the Ontario Grade 8 science curriculum, Matter and Energy: Fluids, where students determine the density of substances and use it to explain why objects sink or float.
Density tells you how much mass is packed into a certain amount of space:
D = m ÷ V · m = D × V · V = m ÷ D
Mass is measured in grams and volume in cm³ (for solids) or mL (for liquids), so density is in g/cm³ or g/mL. Since 1 cm³ = 1 mL, the two units mean the same thing. A block with a mass of 81 g and a volume of 30 cm³ has a density of 81 ÷ 30 = 2.7 g/cm³, which matches aluminum. Rearranging the formula uses the same skills as the two-step equations worksheet.
| Substance | Density (g/cm³) | In water |
|---|---|---|
| Cork | 0.24 | floats |
| Ice | 0.92 | floats |
| Vegetable oil | 0.92 | floats |
| Water | 1.00 | — |
| Honey | 1.42 | sinks |
| Aluminum | 2.70 | sinks |
| Iron | 7.87 | sinks |
| Copper | 8.96 | sinks |
| Gold | 19.3 | sinks |
Every pure substance has its own density, which is why Part A of the density worksheet asks students to identify substances from their density. See density on Wikipedia for more values.
A cube or cylinder's volume can be calculated (see the volume of a cylinder worksheet), but how do you measure a rock? Put water in a graduated cylinder, read the level at the bottom of the curved surface (the meniscus), lower the object in, and read it again.
An object floats in a liquid if it is less dense than the liquid and sinks if it is denser. Water's density is 1.00 g/mL, so candle wax (0.9 g/cm³) floats and a granite pebble (2.7 g/cm³) sinks. It's density that matters, not weight: a heavy log floats while a tiny pebble sinks. Part D of the density worksheet has students calculate each object's density first, then predict.
Liquids that don't mix stack in order of density, with the densest at the bottom. Solid objects dropped in settle at the level where they are denser than the liquid above but less dense than the liquid below:
These questions match the density worksheet PDF, which includes the reference table, graduated cylinders and density column.
Open each part to check the density worksheet answers. The printable key is on the last two pages of the PDF.
These come up often when marking this density worksheet. Part G targets the first one directly.
For more practice, try the chemical and physical changes quiz and the forces and motion quiz.
Yes. The worksheet and its answer key are free to download and print as one PDF, with no account needed.
Density = mass ÷ volume (D = m/V). It's usually measured in g/cm³ for solids and g/mL for liquids, and 1 cm³ = 1 mL.
Use water displacement: read the water level in a graduated cylinder, lower the object in, and read it again. The difference is the object's volume.
Compare its density with the liquid's. If the object is less dense, it floats; if it's denser, it sinks. Water has a density of 1.00 g/mL.
It is written for Grade 8 science (the Fluids unit in Ontario) and also works as Grade 9 review.
Ready to start? Use the Download button above to print the free density worksheet double-sided, and keep the answer key pages for marking.