Fluids Unit Test Study Guide

Fluids Test Study Guide

Please use this guide to help you make study notes and to assist you in studying the material

1. Definitions

Fluid -Fluids are materials that flow

Viscosity -Viscosity is the thickness or thinness of a fluid

Flow Rate - Flow rate measures how quickly fluids move

Cohesion - The attraction between particles of the same substance (e.g., water molecules sticking together).

Adhesion - The attraction between particles of different substances (e.g., water sticking to a glass surface).

Density - The mass per unit volume of a substance (measured in g/cm³ or kg/m³).

Buoyancy -   The ability of an object to float in a fluid 

Buoyant force - The buoyant force is the ability of a fluid to support an object floating in or on it.

Neutral buoyancy -  When the buoyant force is equal to the weight of an object.

Displacement -  To displace means to move something out of its place. In fluids, it means pushing water or air aside when an object is placed in it.

Compression - The reduction in volume of a substance due to applied pressure.

Hydraulics - Using liquid under pressure to transmit force in a system.

Pneumatics - The use of compressed gas to transmit force in a system.

2. The Particle Theory

The 5 points of the particle theory are:

1. All matter is made up of tiny particles.

2. There is space between the particles.

3. Particles are always moving.

4. Particles move faster when heated.

5. Particles are attracted to each other.

Using the table below, name the three states of matter and describe how particles behave in the three different states

3. Changes of state

Fill in the table below for each change of state (I have filled in some for you as a hint).

What is the difference between evaporation and boiling?

Evaporation occurs at the surface of a liquid and can happen at any temperature.

Boiling occurs throughout the liquid at a specific temperature (boiling point).

4. Viscosity and Flow Rate

Describe the relationship between viscosity and flow rate. Use an example to explain. 

The higher the viscosity, the slower the flow rate. Example: Honey has a high viscosity and flows slowly, while water has a low viscosity and flows quickly.

Explain how cohesion and adhesion play a role in determining a fluid’s flow rate

1. High cohesion means particles stick together more, slowing down flow.

2. High adhesion means the fluid sticks to surfaces, also affecting flow rate.

What are the four (4) factors that affect flow rate?

1. Temperature

2. Pressure

3. Surface friction

4. Particle size

If 2 L of water flows out of the tap in 10 seconds, calculate its flow rate.

Flow rate = 2L/10s = 0.2L/s

5. Density

The formula to calculate density is:

Density = mass/ volume

The formula to calculate weight on Earth if given mass is:

W= mg

Calculation examples:

a)A bag of flour with a mass of 20 kg has a weight of?

W = m =20kg

b) Find the density of a pencil with a mass of 6g that takes up 2cm³.

D = 6g/2cm = 3g/cm³

c) What would the mass of an object that has a density of 10 g/mL and has a volume of 7 mL?

m= 7 x 10 = 70

6. How temperature affects density, viscosity and flow rate

Describe what happens to the density of a fluid when temperature decreases. Use real life examples in your description. The formula for density and particles should both be used when explaining. 

Explain why a substance that is more dense will sink in a substance that is less dense.

1. Density decreases as temperature increases because particles move apart. Example: Hot air balloons rise because warm air is less dense than cool air.

2. A denser substance will sink in a less dense substance because it has more mass per unit volume. Example: A rock sinks in water, but oil floats.

7. Buoyancy

Give a scenario when:

1.  An object will sink when its weight is greater than the buoyant force (e.g., a stone in water).

2.  An object will rise when the buoyant force is greater than its weight (e.g., a helium balloon).

3. An object has neutral buoyancy when the buoyant force equals the object's weight (e.g., a fish controlling its swim bladder).

How did Archimedes test to see if the crown was pure gold?

He tested the crown by measuring how much water it displaced compared to pure gold. If the crown displaced more water, it was less dense and not pure gold.

8. Compressibility and pressure on fluids

Using the particle theory, explain why liquids are less compressible than gases.

Liquids are less compressible than gases because liquid particles are already close together, while gas particles have more space between them.

Describe Pascal’s Law

Pressure applied to an enclosed fluid is passed equally in all directions. Example: Hydraulic brakes in cars.

9. Hydraulic and pneumatic systems

What are common components (parts) of all hydraulic and pneumatic systems and explain what each part does.

1. Pump - Moves fluid or air.

2. Valves - Control direction and pressure.

3. Cylinders - Convert pressure into mechanical motion.

Give 2 examples of:

Hydraulic systems  - Car brakes, excavators

Pneumatic systems -  Air brakes, dentist drills

10. Fluids in society and the environment

What are some examples of fluids that negatively impact our environment?

• Oil spills

• Industrial waste

• Pesticides

What impact do oil spills have on wildlife and the environment?

• Harm marine life (coats animals, making movement and insulation difficult).

• Pollutes water and soil, making it toxic for plants and animals.

• Requires costly and time-consuming cleanup efforts.