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Fluids Worksheet with Answers (Grade 8 Science)

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📄 Fluids Worksheet with Answers (Grade 8 Science)

A Grade 8 fluids worksheet with 25 questions (30 marks) and a worked answer key.

By Kris Reddy, Ontario teacher · Updated October 17, 2026 · 25 questions (30 marks) · PDF + answer key

This free fluids worksheet covers three big ideas from the Grade 8 Fluids unit: viscosity, pressure and Pascal's principle. Students rank five liquids from a timed flow race, calculate the pressure of one brick resting three different ways, and use P = F/A to explain snowshoes, high heels and tire pressure.

On the second page they explain why the bottom hole of a leaking tank squirts farthest, solve hydraulic lift problems with drawn pistons, sort devices into hydraulic or pneumatic, explain car brakes, and fix a common mistake about sharp knives. Every answer was checked by computer. To print it, use the Download button above.

Grade 8 Science
30 marks
45–55 minutes
Worked answer key

What's in This Fluids Worksheet

Part	Skill practised	Marks
A	Viscosity: the flow race (bar graph)	5
B	Pressure = force ÷ area (one brick, three ways)	6
C	Pressure in solids, liquids and gases	4
D	Pascal's principle: the hydraulic lift	8
E	Hydraulic or pneumatic?	5
F	Spot the mistake	2

The fluids worksheet supports the Ontario Grade 8 science curriculum, Matter and Energy: Fluids, where students investigate viscosity, explain pressure in fluids and describe how hydraulic and pneumatic systems work.

Viscosity

Viscosity is a fluid's resistance to flowing. A quick way to compare liquids is a flow race: pour equal amounts down the same ramp and time them. The longer a liquid takes, the more viscous it is.

Most to least viscous: Honey → Corn syrup → Dish soap → Vegetable oil → Water

Viscosity is not the same as density. Vegetable oil is less dense than water (it floats, as the density worksheet shows) but it is more viscous. Temperature matters too: warm honey pours faster than cold honey, and cold Canadian winters thicken motor oil.

Pressure = Force ÷ Area

P = F ÷ A · 1 Pa = 1 N/m²

The same force spread over a bigger area makes less pressure. Part B of the fluids worksheet uses one 60 N brick resting three ways:

P: 200 cm² → 3 000 Pa · Q: 100 cm² → 6 000 Pa · R: 50 cm² → 12 000 Pa

That's why snowshoes stop you sinking into snow and why a sharp knife cuts better than a dull one. In liquids, pressure also increases with depth, so water squirts farthest from the lowest hole in a tank:

Pascal's Principle and Hydraulics

Pascal's principle: pressure applied to a fluid in a closed system is passed on equally in all directions. In a hydraulic lift, a small force on a small piston creates a pressure, and that same pressure pushes on a much larger piston:

P = 50 N ÷ 2 cm² = 25 N/cm², so F₂ = 25 × 40 = 1 000 N (20 times the force)

There's a trade-off: the small piston has to move 20 times farther than the big one rises. Hydraulic systems use liquids such as oil because liquids are almost incompressible. Read more about Pascal's law on Wikipedia.

Hydraulic vs Pneumatic Systems

	Hydraulic	Pneumatic
Fluid	Liquid (often oil)	Gas (usually air)
Compressible?	Almost not	Yes
Examples	Car brakes, excavators, dentist's chairs	Jackhammers, nail guns, tire pumps

Part E of the fluids worksheet asks students to sort six devices and explain how car brakes use Pascal's principle.

Fluids Worksheet Practice Questions

These questions match the fluids worksheet PDF, which includes the bar graph, bricks, tank and hydraulic lift diagrams.

Part A – Viscosity: the Flow Race

Flow times down the ramp: Vegetable oil 6 s, Honey 48 s, Water 2 s, Corn syrup 30 s, Dish soap 15 s.

Rank the liquids from most viscous to least viscous. (2 marks)
The honey is warmed and the race is repeated. Predict how its time changes and explain.
Vegetable oil floats on water, but it's more viscous. Explain how viscosity and density are different.
Why do cars in a Canadian winter need a motor oil that stays runny when cold?

Part B – Pressure = Force ÷ Area

Brick P (60 N) rests on a 20 cm × 10 cm face. Find the area and the pressure.
Brick Q (60 N) rests on a 20 cm × 5 cm face. Find the area and the pressure.
Brick R (60 N) rests on a 10 cm × 5 cm face. Find the area and the pressure.
Which way gives the greatest pressure on the ground? Why?
Why can a person in high heels dent a wooden floor when the same person in flat shoes doesn't?
The air in a tire pushes with a pressure of 200 000 Pa on a patch of road 0.02 m². What force does it exert? (F = P × A)

Part C – Pressure in Solids, Liquids and Gases

A 600 N hiker stands in deep snow. Her two boots touch 0.06 m² of snow; her snowshoes touch 0.4 m². Find the pressure in each case and explain why snowshoes stop her sinking. (2 marks)
The tank has three holes, A, B and C. Which stream shoots out the farthest? Explain.
You can squeeze the air in a sealed syringe, but not the water. What does this tell you about gases and liquids?

Part D – Pascal's Principle: the Hydraulic Lift

Diagram: F₁ = 50 N on a 2 cm² piston; the large piston is 40 cm².

Find the pressure in the fluid, the output force F₂, and how many times the force is multiplied. (3 marks)
A garage lift must hold up a 12 000 N car. The big piston is 600 cm² and the small one is 10 cm². What force is needed on the small piston? (2 marks)
The small piston is pushed down 40 cm. How far does the big piston rise? What's the trade-off? (2 marks)
Why do hydraulic systems use a liquid such as oil instead of air?

Part E – Hydraulic or Pneumatic?

Car brakes
Bicycle tire pump
Excavator arm
Jackhammer
Dentist's chair
Nail gun
Explain how pressing a car's brake pedal can stop all four wheels, using Pascal's principle. (2 marks)

Part F – Spot the Mistake

A student says, "A sharp knife cuts better than a dull one because it pushes with more force." Explain the error.

Fluids Worksheet Answer Key

Open each part to check the fluids worksheet answers. The printable key is on the last two pages of the PDF.

Part A answers (Q1–4)

Honey → Corn syrup → Dish soap → Vegetable oil → Water
Its time goes down. Heating makes a liquid less viscous, so it flows faster.
Density = mass per volume; viscosity = resistance to flowing. Oil is less dense but thicker.
Cold makes oil more viscous. Thick oil flows slowly to the engine parts, so a low-viscosity winter oil protects them.

Part B answers (Q5–10)

200 cm² = 0.02 m²; 60 ÷ 0.02 = 3 000 Pa
100 cm² = 0.01 m²; 60 ÷ 0.01 = 6 000 Pa
50 cm² = 0.005 m²; 60 ÷ 0.005 = 12 000 Pa
R (standing on its end, 12 000 Pa): smallest area for the same force.
The heel's tiny area makes a much bigger pressure for the same weight.
F = 200 000 × 0.02 = 4 000 N

Part C answers (Q11–13)

Boots: 600 ÷ 0.06 = 10 000 Pa. Snowshoes: 600 ÷ 0.4 = 1 500 Pa. Bigger area, less pressure.
C, the bottom hole: pressure increases with depth, so water is pushed out hardest there.
Gases are compressible; liquids are almost incompressible.

Part D answers (Q14–17)

P = 50 ÷ 2 = 25 N/cm². F₂ = 25 × 40 = 1 000 N. The force is multiplied 20 times.
P = 12 000 ÷ 600 = 20 N/cm². F₁ = 20 × 10 = 200 N
40 × 2 = 80 cm³ moved, so it rises 80 ÷ 40 = 2 cm. More force, less distance.
Liquids are incompressible, so the push is passed on fully. Air would just squash.

Part E answers (Q18–24)

Hydraulic
Pneumatic
Hydraulic
Pneumatic
Hydraulic
Pneumatic
The pedal's piston pressurizes the brake fluid; the pressure passes equally to bigger pistons at each wheel, which press the pads.

Part F answer (Q25)

Same force, but the sharp edge's tiny area gives a much bigger pressure (P = F ÷ A).

5 Common Fluids Mistakes

These come up often when marking this fluids worksheet. Part F targets the first one directly.

"More pressure means more force." Pressure also depends on area.
Mixing up viscosity and density. Thick isn't the same as heavy for its size.
Forgetting to convert cm² to m². 1 m² = 10 000 cm², so pressures in pascals need m².
Thinking hydraulics give free energy. The force is multiplied, but the distance shrinks.
Swapping hydraulic and pneumatic. Hydraulic = liquid; pneumatic = gas (air).

How to Use This Fluids Worksheet in Class

Lesson 1: Part A of the fluids worksheet after a real flow race with honey, dish soap, oil and water on a tilted tray.
Lesson 2: Parts B–C, with a brick on a sand tray and a pop bottle with three holes.
Lesson 3: Parts D–F, after building a syringe hydraulic arm with two syringes and tubing.

For more practice, try the forces and motion quiz and the scientific method quiz.

Frequently Asked Questions

Is this fluids worksheet free?

Yes. The worksheet and its answer key are free to download and print as one PDF, with no account needed.

What is viscosity?

Viscosity is a fluid's resistance to flowing. Honey is very viscous and flows slowly; water has low viscosity. Warming a liquid usually makes it less viscous.

What is the formula for pressure?

Pressure = force ÷ area (P = F/A). With force in newtons and area in square metres, pressure is in pascals (Pa).

What is Pascal's principle?

Pressure applied to a fluid in a closed container is passed on equally in all directions. Hydraulic lifts and car brakes use it to turn a small force on a small piston into a large force on a large piston.

What grade is this fluids worksheet for?

It is written for Grade 8 science (the Fluids unit in Ontario) and also works as Grade 9 review.

More Free Grade 8 Resources

Ready to start? Use the Download button above to print the free fluids worksheet double-sided, and keep the answer key pages for marking.