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Grade 8 Study Sheet – Fluids
Lesson 1: Introduction to Fluids
* Know the definition and examples of fluids (liquids and gases)
Def: Fluids are materials that have no fixed shape and are free to flow, such as liquids and gases.
Exp: Water
Lesson 2: Characteristics of Fluids (Laminar and Turbulent Flow)
* Know the definition of the particle theory
Def: The particle theory of matter is a theory that explains what matter is made of and how it behaves.
* Know the 5 postulates of the particle theory:
* Matter is made of tiny particles
* Particles have empty spaces between them
* Particles are moving randomly all the time
* Particles move faster and spread farther apart when they are heated
* Particles attract each other
* Know the two types of fluid flow (laminar and turbulent)
* Definition and example of laminar flow, turbulent flow, streamlined.
Def: Laminar flow is smooth, regular, and has parallel fluid movement.
* Exp: many Rivers and Canals
Def: Turbulent flow is choppy and has irregular fluid motion.
* Exp: Rapids (White water rafting)
Def: A streamlined object reduces turbulent flow because it is aerodynamic.
* Exp: dolphins
Lesson 3: Flow Rate and Viscosity
* Know the definition of viscosity, cohesion, adhesion, surface tension, and flow rate
Def: Viscosity is a measure of the resistance to flow in a fluid’s particles
Def: Cohesion is the attraction of a fluids particles between like substances
Def: Adhesion is the attraction of a fluids particles between different substances
Def: Surface tension is the strong attraction between the particles that form the surface of a liquid
Def: Flow rate is a measure of how quickly fluids move; measured in a volume per unit time (for example, L/s)
* Be able to calculate flow rates (refer to Calculating Flow Rate Q's)
For each problem below, calculate the flow rate. Be sure to show your work.
1. It takes 5 s to fill a 1 L container of water from a faucet. What is the flow rate of the faucet in litres per second and in litres per hour? 0.2L/s and 720L/h
2. A baby takes 30 min to drink 150 mL of milk from a bottle. Calculate the flow rate of milk from the bottle in millilitres per minute and in millilitres per second. 5mL/min and 0.08333…mL/s
Lesson 4: Density
* Define mass, weight, and volume
Def: Weight is the force of gravity acting on an object
Def: Mass is the amount of matter that makes up an object
Def: Volume is the amount of space an object takes up
* Be able to explain the 3 different ways to calculate the volume of liquids and solids
1. Measurement - Multiplying its three dimensions together - Length × Width × Height
2. Displacement - Whenever you take a bath, the water rises as you enter the tub. Since you and the water cannot occupy the same space, your body displaces water, which causes the water level to rise.
3. Overflow Can
* What is the mathematical relationship between density, mass, and volume?
* If you increase ↑ the mass and keep the volume the same, then the density increases ↑.
* If you increase ↑ the volume and keep the mass the same, then the density decreases ↓.
* Know why density is considered a characteristic property
Density is a characteristic property because it's a unique and consistent measure for a given substance, regardless of sample size.
* Determine which solids will float in which liquids by looking at their density
- An object that has a higher density than the liquid it floats in will sink
- An object that has a lower density than the liquid it floats in will float.
- With the same density as the liquid, it will stay put depending on where you put it in the liquid, but if another object is put inside, it will move.
Lesson 5: Calculating Density
* Know how to calculate density (review the student note and your density quiz)
* Know the definition of density and its formula.
Def: Density is the degree of compactness of a substance.
* Review what units can be used to measure density
Mass: (g) (kg)
Volume : (L) (mL) (㎤) (㎥)
Lesson 6: Buoyancy and Displacement
* Definition and example of buoyancy
Def: Buoyancy is the upward supportive force on an object in a fluid.
Exp: ship
* Understand how heavy ships float
A heavy ship is able to float on a less dense substance when the ship displaces lots of water using a large, hollow shell, increasing the buoyant force. The hollow shell makes the ship less dense, allowing for it to float.
* Positive, negative, and neutral buoyancy
Positive - If an object is less dense than the fluid, it will float.
Negative - if it's more dense, it will sink.
Neutral - If an object has the same density as the fluid it is in, it will remain suspended in the fluid.
* This is because the buoyant force is determined by the volume of the displaced fluid.
* Define and explain Archimedes’ Principle
Archimedes’ Principle states that the buoyant force is equal to the weight of the fluid that the object displaces.
Lesson 7: Fluids Under Pressure
* What are confined fluids? Definition and example.
Def: Confined fluids are any fluids in a closed system that can move around within the system, but cannot enter or leave it.
Exp: blood in the circulatory system
* Explain confined fluids with the particle theory (the difference between liquids and gases in terms of their ability to compress).
* In a gas, the particles are far apart.
* When a force is applied to the particles in a gas, they are pushed closer together, reducing the volume.
* Gases are very compressible.
* In a liquid, the particles are closer together
* When a force is applied to the particles in a liquid it reduces the volume slightly.
* Liquids are almost incompressible.
* How do car brakes work?
* Pneumatics: Definition and real-life examples
Def: A Pneumatic system uses gases under pressure
Exp: Dentist drills and bicycle pumps.
* Hydraulics: Definition and real-life examples.
Def: A hydraulic system uses liquids under pressure
Exp: The Car braking system and the human circulatory system.
* What makes up a hydraulic system?
A hydraulic system is made up of pumps and conductors.
* What components make up a heart pressure gauge?
* A pump
* (forces fluids through a system)
* Conductors
* (provide a pathway to carry the fluid)
* Valves
* (Keep the fluid moving in the desired direction at the desired time)
* A pressure gauge
* (monitors pressure within the system)
* Arm cuff
* (inflates temporarily to stop blood flow)
* Know the term compressibility
Def: Compressibility is the ability to be squeezed into a smaller volume.
Lesson 8: Fluids in Real Life
* Know how temperature and pressure affect the volume of a gas when compressed
* The particles in gases are far apart, so they can be easily compressed.
* When a gas is compressed, its volume decreases.
* When the temperature of the gas increases, the particles will spread out.
* If a gas is compressed to its limit, it may become a liquid.
* Exp: Propane Gas.
* Explain why heating an aerosol can is dangerous (hint: all about the particles).
1. Heating a can of aerosol increases the speed of the particles.
2. As the particles move faster, they hit the inside walls of the can with increased force, causing the pressure on the walls to build up.
3. If the pressure is strong enough, the walls of the container can explode.
* What is the role of valves in the human circulatory system?
Valves ensure blood flows in the correct direction within the heart and throughout the body, preventing backflow.
* What is one result of a valve that does not work properly in the human circulatory system?
Blood backs up and pools in certain veins. The veins become large and swollen. These are called varicose veins.