Name:_______________

Unit 2 Review Unit 2: Fluids and Viscosity

Terms:

Fluid:________________________________________________________________________________________________________________________

Viscosity:____________________________________________________________________________________________________________________

Flow rate: ______________________________________________________ ______________________________________________________________

WHMIS: _______________________________________________________ ______________________________________________________________

Force:_______________________________________________________________________________________________________________________

Balanced force: _________________________________________________ ______________________________________________________________

Unbalanced force:_______________________________________________ ______________________________________________________________

Mass: _________________________________________________________ ______________________________________________________________

Weight:______________________________________________________________________________________________________________________

Buoyant force:__________________________________________________ ______________________________________________________________

Average density:_________________________________________________ ______________________________________________________________

Pressure: ______________________________________________________ ______________________________________________________________

Pascal (Pa): ____________________________________________________ ______________________________________________________________

Hydraulic system:________________________________________________ ______________________________________________________________

Pneumatic system:_______________________________________________ ______________________________________________________________

Pascal’s Law: ___________________________________________________ ______________________________________________________________

Unit 2 Outcomes:

At the end of this unit students should be able to:

1. Define fluid.2. Compare solids, liquids and gases in terms of shape and volume, and using

the particle theory of matter. Include:a. Shapeb. Volumec. Particle arrangementd. Particle movement

3. Identify examples of fluids in everyday life. Include:a. Compressed air in tiresb. Waterc. Syrup

4. Define viscosity.5. Relate the viscosity of a liquid to the amount of friction between particles.6. Identify examples of viscosity in everyday life. Include:

a. Motor oilb. Paintsc. Foods

7. Define flow rate.8. Identify examples of liquids with different flow rates. Include:

a. Water

b. Dishwashing liquidc. Corn syrup

9. Identify and relate personal activities and potential applications to fluid dynamics. Include:

a. Pancake batterb. Motor oilc. Compare the viscosity of various liquids.

10. Describe factors that can modify the viscosity of a liquid.11. Explain a liquid’s resistance to flow in terms of the particle theory of

matter. Include:a. Strength of attraction between particlesb. Temperaturec. Concentration

12. Describe the relationship among the mass, volume, and density of solids, liquids and gases using

a. the particleb. modelc. of matter.

13. Describe the relationship between states of matter and density using the particle model of matter.

14. Describe the relationship between mass, volume and density.15. Calculate the density of a material, given mass and volume.16. Calculate the mass of a material, given density and volume.17. Calculate the volume of a material, given density and mass.18. Calculate the density of various objects. Include:

a. Irregular shaped objectsb. Liquidsc. Granular objectsd. Regular shaped objects

19. Explain the effects of changes in temperature on the density of solids, liquids, and gases and relate the result to the particle model of matter.

20. Identify examples of density changes in everyday life. Include:a. Hot air balloonsb. Warm vs.c. cool tire pressured. Water in its three states

21. Describe situations in life where the density of substances naturally changes or is intentionally changed. Include:

a. Drying of wood (seasoning of wood)b. Hot air balloonsc. Salt water being easier to float in

22. Describe the movement of objects in terms of balanced and unbalanced forces.

23. Define force.24. Define balanced and unbalanced forces.25. Describe qualitatively the difference between mass and weight.26. Describe the connection between weight, buoyancy, and sinking or

floating.27. Define buoyant force.28. Apply the concept of balanced and unbalanced forces to the buoyancy

and weight of an object to explain why it sinks or floats.29. List examples of materials that may sink or float, depending on the

application. Include:a. Wooden boats vs. a waterlogged stickb. Metal block vs. metal boatsc. A sealed, empty plastic bottle vs. a plastic bottle full of water

30. Define average density.31. Indicate that an object will float if it is less dense than the fluid in which it

is immersed.32. Indicate that an object will sink if it is denser than the fluid in which it is

immersed.33. Provide examples of technologies that have been developed because of

our understanding of density and buoyancy. Include:a. Personal floatation devicesb. Submarinesc. Hot air balloons

34. Describe quantitatively the relationship between force, area and pressure.

35. Define pressure.36. Define the Pascal (Pa) unit.37. Define atmospheric pressure38. Calculate the pressure, given force and area.39. Calculate the force, given pressure and area.40. Calculate the area, given pressure and force.41. Describe the science underlying hydraulic technologies.42. Define hydraulic system.

43. Identify a liquid as an incompressible fluid (ie. Definite volume)44. Define pneumatic system.45. Identify a gas as a compressible fluid (ie, indefinite volume)46. State Pascal’s Law.47. Identify examples of applications of Pascal’s Law. Include:

a. A car lift or hoistb. An hydraulic jackc. Automobile braking system

48. Explain qualitatively the relationship among pressure, volume, and temperature when liquid and gaseous fluids are compressed or heated.

49. Indicate that increasing the temperature of a gas results in an increase in volume (pressure being held constant).

50. Indicate that increasing the pressure on a gas results in a decrease in volume (temperature being held constant).

51. Indicate that increasing temperature of a gas results in an increase in pressure (volume being held constant).

52. Provide examples illustrating the relationship among pressure, volume and temperature when gaseous fluids are compressed or heated. Include:

a. Propane cylindersb. Heating an aerosol can result in an explosion

Goal • Use the following pages to help you review Unit 2.

1. Complete the concept map for question 8 on page 298 of the textbook using key ideas you learned in Chapter 7.

2. Complete this concept map for the Unit 3 Review on page 380 of your textbook, question 1.

3. Create a list of 10 words or phrases from the descriptions below. Then find the words and phrases in the puzzle.

1. The pull, or force, of gravity acting on an object (6 letters)

2. The upward force on objects submerged in or floating on fluids (8 letters)

3. The total mass of all substances thatmake up the object divided by the totalvolume (7 letters, 7 letters)

4. The force acting on a certain area of asurface (8 letters)

5. The unit for pressure (6 letters)

6. The ability to be squeezed into a smaller volume, or space (15 letters)

7. Anything that causes a change in themotion of an object (5 letters)

8. The amount of matter in an object(4 letters)

9. Systems that use gasses to transmit forces (9 letters, 7 letters)

10. The study of pressure in liquids(10 letters)

Unit 2 Practice QuestionsWhat to Do

Circle the letter of the best answer.

1. Which of the following statements regarding particle theory is false?A. All matter is made up of very small particles.B. All particles are attracted to one another with equal strength.C. Particles that make up matter are always moving.D. There are spaces in between particles.

2. What are you calculating if you divide the mass of a substance by its volume?A. buoyancyB. densityC. pressureD. weight

3. Which of the following statements is true of Archimedes’ principle?A. The buoyant force acting on an object equals the weight of the fluid displaced by the object.B. The buoyant force acting on an object is greater than the weight of the fluid displaced by the object.C. The buoyant force acting on an object is less than the weight of the fluid displaced by the object.D. The buoyant force acting on an object is not equal to the weight of the fluid displaced by the object.

4. Why do objects float more easily in salt water than in fresh water?A. The density of fresh water is greater than that of salt water.B. The density of salt water is 1.00 g/mL.C. The density of salt water is greater than that of fresh water.D. The particles of fresh water are packed together more tightly than those in salt water.

5. Two different tennis balls (one filled with air, one with water) are struck with the same amount of force. The tennis ball filled with air can absorb much more force than

the similar tennis ball filled with water. Which of the following statements is the reason for this result?

A. Air is compressible, while water is not.B. Air is not compressible under ordinary circumstances.C. The force of gravity is greater on the water-filled tennis ball.D. The forces on the air-filled tennis ball are more out of balance.

6. A submarine sinks when which of the following occurs?A. Its weight is equal to the buoyant force.B. Its weight is greater than the buoyant force.C. Its weight is less than the buoyant force.D. Water is released from its ballast tank.

Match the Term on the left with the best Descriptor on the right.Each Descriptor may be used only once.

Term Descriptor

_____ 10. compressibility_____ 11. condensation_____ 12. hydraulic system_____ 13. low viscosity_____ 14. mass_____ 15. pneumatic system_____ 16. pressure_____ 17. sublimation

A. a device that transmits a force through a liquidB. ability to be squeezed into a smaller spaceC. change from gas to liquidD. change from liquid to solidE. change from solid to gasF. force divided by areaG. high flow rateH. low flow rateI. remains the same anywhere in universeJ. vacuum cleaner

Short Answer Questions

1. Explain the differences among a solid, liquid, and gas in terms of shape and volume._______________________________________________________________________________________________________________________________________________________________________________________________________________

2. List the main points of the particle theory of matter._______________________________________________________________________________________________________________________________________________________________________________________________________________

3. A boat travels along the water at a steady speed.(a) Are the forces on the boat balanced or unbalanced? Explain.__________________________________________________________________________________________________________________________________________

(b) Draw a diagram of the boat andlabel all the forces acting on it.

4. A student performs an experiment with three balloons. One is filled with air, one with water, and one with cement that is allowed to harden. The student records the following observations:– When force is applied, the balloon filled with air reduces in volume.– When force is applied, the balloon filled with water can be deformed, but does notreduce in volume.– The balloon filled with cement cannot be deformed or reduced in volume with applied force.Explain why the student observed different results for the three balloons._______________________________________________________________________________________________________________________________________________________________________________________________________________

23. (a) How are pneumatic systems and hydraulic systems similar? __________________________________________________________________________________________________________________________________________

(b) How are they different?__________________________________________________________________________________________________________________________________________

24. Solve the following problems:(a) A 40 cm3 cube of pure nickel is measured by a student to have a mass of 356 g. What isthe density of the nickel?

_____________________________________________________________________

(b) A 200 mL sample of alcohol has a mass of 158 g. What is the density of the alcohol?

_____________________________________________________________________(c) A football player with a weight of 125 kg stands on a 0.5 m by 0.5 m scale. Whatpressure does the platform of the scale exert on the spring below?

_____________________________________________________________________

(d) The bottom of a woman’s shoe heel measures 0.02 m by 0.04 m. If the woman with a weight of 56 kg balances on a single heel, what pressure does she exert on the groundbelow?

_____________________________________________________________________

Extra Review: (Viscosity, Density and Pressure)Complete the following calculations:

a) Calculate the flow rate for each of the following substances:Substance Length of Ramp (cm) Time to Reach End of Ramp

(s)

A 40 2.5

B 40 10

C 40 13

b) Rank the substances from lowest to highest viscosity.

2. You collect 5000 mL of a gas in a balloon. If the gas of the balloon has a mass of 10.0g, what is the density of the gas? Identify the gas with Table 8.1 in page 312.

3. What is the mass of 2000 mL of seawater? (Table 8.1 on page 312)

4. A piece of copper has a density of 8.92g/cm3 and a mass of 15.5g. What is its volume?

5. If you are holding a lead weight in your hand with a weight of 1.2 N and the bottom

of the weight has an area of 0.24 m2, what is the pressure on your hand?

6. An aquarium with a bottom area of 3.5 m2 has a water pressure of 3600 Pa. What force is the water exerting on the bottom of the aquarium?

7. A large stack of wood is sitting at a construction zone with a weight of 36300N. If the average pressure of the wood is 40000 Pa on the ground, what is the area of the stack of wood?

Complete the following questions regarding theory:1. What is Pascal’s Law? Give an everyday example of Pascal’s Law.

2. What is the difference between a hydraulic system and a pneumatics system?

3. What is hydraulic multiplication? Describe a time that we used hydraulic multiplication in class.

4. Would pressure be greater on the ground or at the top of a mountain? Explain.

5. In the ocean where would pressure be the highest and lowest? Explain.

6. You are on a pond during winter and the ice begins to crack, how do you get to safety without falling through the ice?

7. Explain how the swim bladder of a fish works? (hint: think about the Cartesian divers we made in class)

8. Is it better to throw a wet log on a fire or a dry log? Explain using density in your answer.

9. How do we measure the density of an irregular shaped object like a beach rock?

10. When a helium balloon is placed outside in the cold, what happens to its particles? When it is brought back inside in the warm, what happens to its particles?

11. Is you are making pancakes and they are too runny, what can be said about its viscosity? How can you fix the problem?

12. How does a hot air balloon float? (Hint: Think about the teabag demonstration we did in class)

Unit 2 Notes Fluids

Chapter 7

Fluid: A substance that flows.  The particles in the matter can move around.  This includes gases and liquids.

The States of Matter

Solids Liquids GasesDefinite shape Indefinite shape Indefinite shape

Definite volume Definite volume Indefinite volumeParticles close together Particles close together Particles distant

Particles vibrate in place, neighbors always

the same

Particles free flowing, free to move around and have different

Particles move randomly around

neighbors

The Particle Theory of Matter1) All matter is made up of tiny particles2) All particles in a pure substance are the same; but different than particles in other substances.3) There is space between the particles.4) Particles are always moving, the more energy the particle has the faster it moves.5) Particles in a substance are attracted to each other. The strength of the attraction depends on the type of particle.

Viscosity: The term for the resistance to the flow of a liquid.  If a fluid has a low viscosity it will flow quickly and be "runny" like water.  A high viscosity will be slow and thick, like pancake syrup.Factors that Affect Viscosity1) Temperature and viscosity (Liquids): Since the temperature of a substance affects how much a particle moves around, the higher its temperature the faster it moves and the further away the particles are from each other.  So the higher the temperature the lower the viscosity.  Ex: warm molasses flows faster than cool molasses.2) Temperature and viscosity (Gases): Gases have particles that are already very far apart so little friction between them.  As you heat a gas you make more and harder collisions between the particles and the gas actually becomes more viscous.

3) Concentration and viscosity: Concentration is a term for the amount of substance that is dissolved in a volume of another substance. With the KoolAid activity the higher concentration tasted stronger and appeared darker.If you have a larger amount of substance dissolved, there are more particles and more friction between them.  So a higher concentration gives you a higher viscosity.  Ex: Maple syrup from the tree is very runny, when you boil it down you are removing water.  The final product is more concentrated and thicker.4) Attractive force and viscosity:All particles have an attractive force on each other.  This strength is not always the same strength for all substances.  So a substance with large attractive forces will have a high viscosity.5) Particle size and viscosity:The size of the particle also has an effect on the viscosity of a fluid.  Larger particles have a harder time moving around than smaller particles do.  So a fluid with large particles is more viscous than one with smaller particles.  Ex: Margarine that you put

on your toast can be soft or hard.  The softer margarine has smaller particles of the same type as the hard, so they taste the same but not the same viscosity. Motor Oil... A lesson in viscosityMotor oil needs to be a particular viscosity to do its job.  If it is too runny it will not protect the parts of the engine that rub against each other.  If it is too thick then it will not get around the engine and coat all the parts that it is supposed to protect.We know that the temperature affects the viscosity of liquids, so motor oil needs to be a certain type to operate at certain temperatures.In Labrador where it is cooler we need a thinner (less viscous) oil because at the lower temperatures when starting the vehicle the oil will still be runny enough to coat the parts.  On the island we can still use the thicker oil because it does not get as cold.Oil numbers: 5W-30, 10W-30... The lower the number in front of the W means an oil for colder start temperatures which would be a thinner oil.  The second number (30) is the high temperature operating number of the oil for when you are driving around.  The "W" is for WINTER and means that the oil is rated for cold weather. Flow RateThis is the speed at which fluids get from one place to another.  It is used to compare viscosity, since viscosity is hard to measure directly. Flow Rate can be measured in cm/s like we did in our activities and labs. For example: cold molasses might have a flow rate of 1 cm/s but warm molasses might have a flow rate of 3 cm/s. The higher the flow rate the less viscous the fluid.  

Chapter 8We have already talked about density in Unit 1, where we compared the density of fresh and salt water.  Now we will talk about density in greater detail.Density: The amount of mass in an amount of volume for a substance. When we work with mass we use units like grams or kilograms.  We say that something has a mass of 500g or something as a mass of 80kg.  This is the measure of the amount of matter in the substance.When we work with volume we use units like milliliters or liters or even centimeters cubed.  We would say that something takes up a volume of 250ml, or maybe 5L, or maybe 300cm3.  It is important to note that 1ml of water is 1cm3 of water and has a mass of exactly 1g.  This is how we came up with the unit of the gram. Mass vs WeightMass and Weight are not the same thing.  Mass is a measure of how much matter something has and weight is a measure of how much gravity pulls that mass down.When we ask how much a person weighs we are actually asking for their mass.  A person has the same mass anywhere in the universe but has a different weight based

on what planet they are on.  You have the same mass on the moon as on earth but your weight is much less. DensitySomething has a high density if it has a lot of mass in a small volume.  Lead is an example of this; even a small piece will feel heavy to you.  It has a high amount of mass in a small volume.  Something that has a low density like marshmallow will have little mass but take up a lot of space.So how do we calculate density?  If mass and volume are important then we need them to calculate density.  Since it is an amount of mass for a given volume (mass per volume) we have to divide the mass by the volume.

D = m/VDensity = Mass / Volume

Let’s look at an example5kg / 2L = 2.5kg/L

That is to say 2.5 kilograms of mass for every Liter of space taken up by the material. Figuring out volumeAn easy way to determine the volume of something that is not a geometric figure is to use DISPLACEMENT.  This is where you put it in a container filled with water and see how much water it moves out of the way.  The amount of water would be the same as the volume of the object.Density change in everyday lifeIf you can make the particles of a substance move further apart you can have its mass the same and increase its volume.  This will decrease its density.  On the other hand if you can make its particles move closer together you can increase its density.Examples:  Your car tires need more air in them during the winter because the cold makes the air more dense and your tires are more flat.  A hot air balloon uses density too.  Heating the air makes it less dense than the air outside the balloon and the balloon rises.  Another example is when you leave wood out to dry that you are going

to burn.  It loses water which makes it lighter and it also makes it better to burn since it has some of its water removed.One of the most interesting examples of density is water.  As you cool down water it gets more dense like any liquid but when it freezes into ice which is a solid, it is actually less dense than it was as a liquid.  This is why ponds freeze over on the top and your ice cube floats in your glass.  Water is most dense at 4 degrees, after that it gets less dense until it gets to 0 where it actually becomes ice. 

Chapter 9Force:  A force is a push or a pull.  Things can exert a force by touching each other like when you pull on a rope, or they can act over a distance like with magnets or gravity.  A force can make things move or keep them from moving. Newton: Isaac Newton discovered how gravity works and because gravity is a force, the unit for force is called the Newton (N). Balanced and Unbalanced forcesThere is often more than one force acting on an object.  If all the forces in one direction cancel each other out it is balanced and is either stopped or moves at a constant speed.  If the forces do not cancel each other out it will speed up or slow down in that direction. Mass vs. Weight revisitedMass we know is the measure of the amount of matter in a substance and is measured in units like Kilograms.  Weight however, is the pull of gravity on a piece of matter and can be different on different planets for example.  It is measured in Newton’s (N) as we said above. BuoyancyThis is the force that water or any other fluid puts on objects as the fluid is moved out of the way.  For our rubber ducky example the ducky only pushes a little water out of the way as it sinks into the surface of the water.  The volume of water pushed out of the way has the same weight as the weight of the ducky.Anything will float if it can push its weight of water out of the way.  If it can’t do this then the buoyancy force will be smaller than the force of gravity pulling down and you will sink. Buoyancy and DensityBuoyancy and density are related.  If an object is less dense than the fluid that it is in it will always float, no matter what its shape. A piece of wood is a good example of this. However, when the object is denser than the fluid, it has to have a shape that allows it to displace its weight in water and not fill up with the fluid.  A steel ship is a good example of this.The second example brings in an idea of Average Density.  The steel in the ship is denser than water but the ship also has air in it which is much less dense than water.  So the ship on average is less dense than water.  Only when water gets in, pushes air out and makes the ship heavier does its density go above that of water and it sinks.

This concept of average density is used in nature and by humans.  Fish have a swim bladder that they can put air into and out of that changes their density and allows them to swim up and down.  Submarines also use this.  They have tanks that they can pump water into to sink and pump water out of to rise.  Page 341 shows a great diagram of this on the text.Pressure and FluidsPressure: A force applied over an area.  Pressure is measured in Pascals (Pa), however 1Pa is a very small amount so we often use the unit kPa (Kilopascals) which is 1000Pa.How do we get pressure?  We need a force to have pressure, if there was no force then there would be no pressure.  We also need an area to apply that force.  Remember that force is measured in Newtons (N) and area is usually measured in meters squared m2.How do we get a really large pressure?The larger the force the greater the pressure.The smaller the area the greater the pressure, think popping balloons with pins and how it is much easier than popping them with your finger.So, what is our formula for Pressure... how do we get a huge pressure from a force and an area?To get the largest number you need to multiply by the force and then divide by the area since the smaller the area the greater the pressure.Pressure = Force/Area P=F/AWe have done calculations earlier in the unit involving density, the calculations using pressure are handled the same as density with the same power triangle but with different symbols in it.

Pascal's Law

Pascal was a scientist and is who the unit for pressure is named after.  His law states that if you apply a force to a fluid that is enclosed, then that force is applied over the entire container.We use this law in our everyday life to our advantage in 2 main ways, with Hydraulic and Pneumatic systems.1) Hydraulic systems:  These use liquids.  They have a liquid in a container, apply a force at one point in the system and have it move something in another part of the container.  Heavy equipment like  a bulldozer and back end loaders are good examples of these systems.

2) Pneumatic systems:  These use gases.  Just as in above only that we know that gases can be compressed.  These are used in things like the shocks of your car, or all the air tools you can think of like an impact gun. Temperature, Pressure and Volume of GasesTemperature has an effect on volume of gases as we already know.  As you increase the temperature on a gas you make its volume increase and when you decrease the temperature you make the volume decrease.  So increasing temperature will increase the pressure on a gas.  On the other hand decreasing the temperature will decrease the pressure.For example a Helium balloon will be a certain size when it has an amount of gas in it.  This is because the force pressing out is the same as the pressure pushing in.  If you heat the Helium in the balloon the balloon will get bigger because there will be more pressure on the inside and the balloon will grow to spread out the force over a bigger volume.  If you put too much pressure on the sides of the balloon it will POP.