Year 9 · Science
Density and pressure worksheet for Year 9
For the solids, liquids and gases lesson, start with tasks 1 and 2. They compare the three states and explain gas compression. Tasks 3 to 6 add density and warming if you want to go further. You can type here, choose to save your work in this browser, or print it.
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TheLearnDenYear 9 · Science
Density, pressure and the particle model
Part 1 of 3 · Density and pressure
Show your thinking. Particle diagrams are models; dots are not to scale.
Name (optional):
1 Quick recap
Complete the table. Use these words where they fit; you may use a word more than once: fixed, container’s shape, fills the container, close, far apart, vibrate, move past one another, all directions.
Show a planning hint
Think about what stays fixed in each state, then describe particle arrangement and movement.
| State | Shape | Volume | Particle arrangement | Particle movement |
|---|---|---|---|---|
| Solid | ||||
| Liquid | ||||
| Gas |
2 Same gas, less room
The syringe is closed. The amount of gas and its temperature stay the same as its volume decreases.
Do particles become smaller, or do the gaps between them decrease? Explain.
With mass unchanged, what happens to density when volume decreases? Explain using mass divided by volume.
What happens to pressure? Explain how the unchanged amount of gas and smaller volume affect wall collisions.
Show a planning hint
Keep the amount and temperature fixed in your explanation.
TheLearnDenYear 9 · Science
Density, pressure and the particle model
Part 2 of 3 · Density and pressure
Show your thinking. Particle diagrams are models; dots are not to scale.
Name (optional):
3 Calculate density
A sample has mass 24 g and volume 8 cm3. State the formula, show working and give density.
A second sample has mass 30 g and volume 30 cm3. Which sample is denser? Show both calculations with units.
Show a planning hint
Use density = mass ÷ volume, and include g/cm³ in both answers.
4 Pressure when a gas is warmed
The same amount of gas is in a sealed, rigid container. Its volume stays the same before and after warming.
Why does pressure rise? Mention particle speed, collisions with the walls and force per unit area. Do not say the particles grow.
Show a planning hint
Explain the collision mechanism step by step; distinguish movement, force on the wall and pressure.
TheLearnDenYear 9 · Science
Density, pressure and the particle model
Part 3 of 3 · Density and pressure
Show your thinking. Particle diagrams are models; dots are not to scale.
Name (optional):
5 Check the model
Sam says: 'When a gas is compressed, its particles get smaller.' Explain what is wrong and what a before-and-after drawing should keep the same and change.
Show a planning hint
Your before and after sketches should have the same count and equal dot sizes.
Before compression
Use equal-sized dots for the particles.
After compression
Keep count and dot size the same.
6 Compare two gas changes
Both cases start with the same amount of gas. In A, the gas is compressed to half its original volume at the same temperature. In B, it is warmed in a sealed, rigid container at a fixed volume. Particle size and count stay the same.
For each case, say what happens to density and pressure. Explain why the causes of the pressure changes differ. Do not calculate a pressure ratio.
Show a planning hint
Compare a volume change at fixed temperature with a motion change at fixed volume.
| Condition or result | A: compressed | B: warmed |
|---|---|---|
| Density | ||
| Pressure |
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