Canada Grade 8 Science Fluid Properties of fluids

What is the term for the resistance of a fluid to flow?

• Density

• Buoyancy

• Viscosity

• Pressure

Answer explanation

Viscosity is the term that describes a fluid's resistance to flow. It indicates how thick or sticky a fluid is, affecting how easily it moves. Density refers to mass per volume, buoyancy relates to floating, and pressure is force per area.

Which property of a fluid causes objects to float or sink?

• Viscosity

• Buoyancy

• Surface tension

• Adhesion

Answer explanation

Buoyancy is the property of a fluid that determines whether an object will float or sink. It is the upward force exerted by the fluid, which counteracts the weight of the object. If buoyancy is greater than the object's weight, it floats.

What happens to the pressure in a fluid as depth increases?

• It decreases.

• It increases.

• It remains the same.

• It fluctuates randomly.

Answer explanation

As depth increases in a fluid, the weight of the fluid above exerts more force, leading to an increase in pressure. Therefore, the correct answer is that pressure increases with depth.

What is the principle that explains why airplanes can fly?

• Archimedes’ principle

• Pascal’s principle

• Bernoulli’s principle

• Newton’s third law

Answer explanation

Bernoulli’s principle explains that as the speed of air over the wings increases, the pressure decreases, creating lift. This lift allows airplanes to fly by balancing the forces of lift and weight.

Which of the following is NOT a fluid?

• Air

• Water

• Ice

• Oil

Answer explanation

Ice is a solid, while air, water, and oil are all fluids. Fluids can flow and take the shape of their container, which ice cannot do.

What is surface tension?

• The density of a fluid.

• The cohesive force at the surface of a fluid.

• The viscosity of a fluid.

• The pressure at the bottom of a fluid.

Answer explanation

Surface tension is the cohesive force at the surface of a fluid, which causes it to behave as if its surface is covered with a stretched elastic membrane. This is why small objects can float on water despite being denser.

What does Archimedes’ principle state?

• Pressure increases with depth in a fluid.

• Fluids flow from high pressure to low pressure.

• An object submerged in a fluid experiences an upward force equal to the weight of the displaced fluid.

• The volume of a fluid changes with temperature.

Answer explanation

Archimedes' principle states that an object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces, which explains why objects float or sink in fluids.

What unit is commonly used to measure pressure in fluids?

• Litres

• Pascals

• Grams

• Joules

Answer explanation

Pressure in fluids is commonly measured in Pascals (Pa), which is the SI unit for pressure. Litres measure volume, grams measure mass, and joules measure energy, making Pascals the correct choice for pressure.

What happens to a gas when it is compressed?

• Its density decreases.

• Its volume decreases.

• Its mass decreases.

• Its viscosity increases.

Answer explanation

When a gas is compressed, its particles are forced closer together, resulting in a decrease in volume. This is a fundamental property of gases, as they occupy more space when not compressed.

Why do objects feel lighter in water?

• Water has no gravity.

• Water exerts an upward buoyant force.

• Water reduces the object's mass.

• Water eliminates friction.

Answer explanation

Objects feel lighter in water because water exerts an upward buoyant force, counteracting the force of gravity. This buoyancy makes the object seem lighter than it does in air.