Science 8
Fluids Unit
Chapter 4 – The Properties of Fluids
Pages 100 – 139
KEY
Section 4.1 – A Close-Up Look at Fluid Flow (page 101 - 104)
1. Define fluids and state what is considered a fluid: A fluid is a substance that can flow.
Liquids and gases are considered a fluid.
2. Why do fluids flow? Fluids flow because a force is exerted on them.
3. Define flow rate: How quickly a fluid flows in a given amount of time.
4. What are the three states of matter? Solid, liquid, gas
5. State three points of the kinetic molecular theory.
 All matter is composed of particles and there are spaces between those
particles
 Particles are in constant motion
 There are forces of attraction among particles
6. What causes a substance to change its state? A change in temperature (increase or
decrease). Putting more or less energy into a substance.
7. Particles in a solid are packed so close together they can only vibrate and move slowly.
Particles in a liquid can slide past each other and move quickly.
Particles in a gas can also slide past each other/move freely and move very quickly.
8. Melting is the process of a solid changing to a liquid.
Sublimation is the process of a solid changing directly to a gas.
9. Evaporation is the process of a liquid changing to a gas.
Solidification is the process of a liquid changing to a solid.
10. Condensation is the process of a gas changing to a liquid.
Deposition or sublimation is the process of a gas changing to a solid.
11. Explain how the terms evaporation and condensation are related. Both are dealing
with liquids and gases. Evaporation occurs when a liquid is heated and
condensation occurs when a gas is cooled.
12. What is the opposite of each of the following terms:
 Evaporation – condensation
 Solidification – melting
 Sublimation – sublimation/deposition
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13. Use the kinetic molecular theory to explain why solids do not flow. Solids do
not flow because their particles are tightly packed and only vibrate;
therefore, they can not flow past each other.
Section 4.1 – Forces
1. Define force: A force is a push or pull.
2. What units are used to measure forces? Units – Newtons (N)
3. Explain the difference between contact and non-contact forces. In contact forces, two
objects physically touch for the force to occur. In non-contact forces, objects do
not have to touch.
4. Define the several well known forces and state whether they are contact or non-contact
forces.
a) Friction – works to slow down or stop motion due to surfaces rubbing against
b)
c)
d)
e)
each other. CONTACT
Elastic force – is exerted when a spring-like object returns to normal shape
after being compressed or stretched. CONTACT
Gravity – force of attraction between objects because they have mass. NONCONTACT
Magnetic – the push or pull on metals and compounds such as iron, nickel,
and cobalt. NON-CONTACT
Static Electricity – pushing and pulling forces caused by things that are
electrically charged. NON-CONTACT (although, can also be contact)
5. What force slows or restricts movement? Why? Friction. It rubs in the opposite
direction; therefore slows down movement.
Section 4.2 – Fluid Flow around Objects (pages 105 – 106)
1. Describe how laminar flow is different from turbulent flow. In laminar flow, a fluid
travels in straight, or almost straight, lines. In turbulent flow, the fluid has
irregular patterns since the fluid is unable to flow in straight lines.
2. List some examples of laminar flow. A deep river, streamlined or aerodynamic
cars/bikes/planes, dolphins
3. List some examples of turbulent flow. A shallow river, building and trees
4. What is the difference between drag and streamline. Drag is a force that acts to slow a
body through a fluid while streamline are shapes that allow for laminar flow.
Section 4.3 – Viscosity: A Property of Fluids (pages 107 – 108)
1. Define viscosity: resistance of a fluid to flowing and movement.
2. Answer each question to explain the reason for different viscosities.
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a) The property of fluids that makes the particles hold together because they are attracted
to each other is called? cohesion
b) The attraction between particles of a fluid and another substance so that the fluid clings
to it is called? adhesion
c) The water particles at the surface attract each other in a way that makes the surface
act like a skin. This effect is called? Surface tension
3. What is the unit for viscosity? In Science 8, how will you describe viscosity? The unit for
viscosity it Poise. In Science 8, fluids that are resistant to flow will have high
viscosity and fluids that aren’t as resistant to flow will have low viscosity.
4. Make a list of substances that are useful because of their viscosity. Complete Table 1 found
below.
Substance
Vinegar
Ketchup
Syrup
Shampoo
Juice
Table 1
Viscosity
Very thin/ Low V
Thick/ High V
Thick/High V
Thick/High V
Very thin/Low V
Usefulness of the Viscosity
Easy to sprinkle or mix with other substances
Good to put on and keep on food.
Good to keep on pancakes
Good to make a lather
Easy to swallow
5. How does temperature affect viscosity? As the temperature increases, the object
will become less viscous (thinner); therefore, have a low viscosity. As temperature
decreases, the object will become more viscous (thicker); therefore, have a high
viscosity.
6. How does the thickness of a fluid compare with its viscosity? Give an example. The thicker
the fluid, the higher the viscosity. Ketchup is very resistant to flow.
7. What does the viscosity of a substance tell you about its flow rate? The higher the
viscosity, the slower the flow rate.
8. “Molasses has high viscosity”. Explain what this statement means. Molasses is very thick;
therefore, it will have a high viscosity.
9. Television commercials advertising motor oils often use the phrase “our oil resists thermal
viscosity breakdown”.
a) What does the word thermal mean? Heat, adding heat
b) What does breakdown mean? To break apart
c) Explain what they are saying based on what you have learned about viscosity. When
adding heat, the oil will not become thin; therefore, will still have a high
viscosity.
10. Part(s) of each statement below is false. Rewrite each statement to make it true.
a) As the viscosity of a fluid decreases, its flow rate increases.
b) Molasses has the higher viscosity than water.
c) As a liquid is heated, its viscosity decreases.
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d) A thicker fluid is more resistant to flow than a thin fluid. Therefore, it flows slower
than a thinner fluid.
Section 4.5 – Measuring Matter: Mass, Weight, and Volume (pages 113 – 115)
1. Matter is anything which has mass and volume.
2. Define mass and state its units. Mass is the amount of matter in a given object. Its
units are grams or kilograms.
3. Use the following information to answer questions a) and b): 1000 grams (g) = 1 kilograms
(kg)
a) To convert grams to kg, divide the number of g by 1000.
 3000 g = 3 kg
 210 g = 0.21 kg
 52 g = 0.052 kg
b) To convert kilograms to g, multiply the number of kg by 1000
 0.7 kg = 700 g
 13 kg = 13,000 g
4. Explain the difference between mass and weight. Mass is the amount of matter in an
object and weight is the measurement of the force of gravity on an object (that object
will have a certain mass + force of gravity).
5. Explain how you find mass using an indirect measurement. Measure the mass of an
empty beaker, pour a liquid into the beaker, measure the mass of the beaker and
liquid, subtract the beaker amount from the beaker + liquid.
6. Define volume and state its units. The amount of space that an object occupies. It is
measured in mL, L, and cm3.
7. Use the following information to answer questions a) and b): 1000 milliliters (mL) = 1 liter (L)
and 1 mL = 1 cm3
a) To convert mL to L, divide the number of mL by 1000.
 3000 mL = 3 L
 112 cm3 = 112 mL = 0.112 L
 15 cm3 = 15 mL
b) To convert L to mL, multiply the number of L by 1000.
 2 L = 2000 mL = 2000 cm3
 0.15 L = 150 mL = 150 cm3
8. What formula can we use to measure the volume of a rectangular solid object? What type of
measurement is this? L x w x h; direct measurement
9. Calculate the volume of a rectangular solid with the length of 5 cm, a width of 6 cm, and a
height of 3 cm? Show your work. 5 cm x 6 cm x 3 cm = 90 cm3
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10. What is the volume of a textbook that is 10 cm wide x 15 cm long x 3 cm thick? Show your
work. 10 cm x 15 cm x 3 cm = 450 cm3
11. When using a graduated cylinder, the liquid is measured at the bottom of the level of the
liquid. This is a curved surface called the meniscus.
12. What formula is used to calculate the volume of an irregular object? What type of
measurement is this and what is it called?
Volume of object = (volume of water + object) – volume of water
This is an indirect measurement and it is called the displacement of water
13. A graduated cylinder contains 30 mL of water. A stone is carefully slipped into the cylinder.
He level of the water reaches 48 mL. What is the volume of the stone? Show your work. 48
mL – 30 mL = 18 mL The volume of the stone is 18 mL
14. A diamond has the volume of 22 mL. When placed in water, the water had risen to 42 mL.
What level was the water initially in the graduated cylinder? Show your work. 42 mL – 22
mL = 20 mL. The level of the water was initially at 20 mL
Section 4.7 – Density: Another Property of Fluids (pages 119 – 122)
1. Define density and state its units: the mass of a substance per unit volume of the
substance. Its units are grams/mL
2. What is the formula for density? D = m/V; Density = mass/volume
3. What is the density of water and what does it mean? 1.00 g/mL. This means that for
every gram of water fits into 1 mL of space.
4. What is the approximate density of ice? 0.92 g/mL
5. Why does ice float in water? Ice is less dense then water; therefore, it will float on
water.
6. Suppose that alcohol, glycerol, water, and gasoline are placed in a tall container. What order
would you expect to find them starting from the bottom of the container to the top? Glycerol
(1.26 g/mL), water (1.00 g/mL), alcohol (0.79 g/mL), and gasoline (0.69 g/mL)
7. Gold has a density of 19.3 g/cm3. Will it float or sink in water? Why? Gold will sink in
water because it is more dense then water.
8. The volume of a rock was determined by the displacement method to be 550 cm3. It has a
mass of 55 g. Calculate the density of the rock. Show your work.
D = m/V D = 55g/550 cm3 = 0.10 g/cm3
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9. An unknown substance found below is measured and weighed. It has a mass of 200 grams.
What is its density?
a)
Mass = 200 grams
Volume= l x w x h = 8.2 x 2.0 x 4.5
= 73.8 cm3
8.2 cm
b)
Density = mass/volume
= 200 grams/ 73.8 cm3
= 2.71 g/cm3
2.0 cm
c) Will this object sink or float in water?
sink. Why? Its density is more than
waters’.
4.5 cm
It will
Table 2. Some
known densities of
metals
Metal
Density
Aluminum 2.7 g/cm3
Copper
8.9 g/cm3
Titanium
4.5 g/cm3
Mercury
13.8 g/cm3
Brass
8.4 g/cm3
Steel
7.9 g/cm3
d) What might this material be given the list of known densities in Table 1? aluminum
10. A sample of ironwood has a volume of 3500 cm3 and a density of 1.2 g/cm3. What is the mass
of the ironwood? Show your work. m = D x V m = 1.2 g/ cm3 x 3500 cm3 = 4200 grams
11. A titanium bicycle frame has a mass of 3000 grams. What volume of titanium would you need
to pour into the mold to make this frame? Titanium density is 4.5 g/cm3. Show your work. V =
m/D V = 3000 grams/4.5 g/ cm3 = 666.7 cm3
Section 4.10 – The Ups and Downs of Buoyancy (pages 127 – 129)
1. Define buoyancy and give two examples: An upward force that a fluid exerts on
an object. Examples: A person in water; A balloon filled with helium
2. What other force acts on an object in fluid? Force of gravity
3. Explain Archimedes’ principle. The buoyant force on an object immersed in a
fluid is equal to the weight of the fluid that the object displaces. When an object is
immersed in water or another fluid, the volume displaced equals the volume of the
object. Knowing the mass and volume, can calculate the density of an object.
4. How can you modify a dense solid substance to make it float in a less dense fluid?
Design it so that the object contains a larger volume of air, therefore decreasing the
density.
Section 4.11 – How and Why Do Things Float (pages 130 – 132)
1. Explain how positive, neutral, and negative buoyancy occurs in liquids. If an object
rises in a fluid, it has positive buoyancy. The force of gravity acting on the object is less
than the buoyant force. If an object remains level in a fluid, the force of gravity and the
buoyant force are equal and it has neutral buoyancy. If an object sinks in a fluid, then
the force of gravity is greater than the buoyant force.
2. Give examples of real-life situations that have positive, neutral, and negative
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buoyant forces. Positive buoyancy – a balloon rising, paddling in a canoe, swimming in a
wetsuit at the surface of a lake; Neutral buoyancy – fishing swimming in a lake, a
submarine maintaining a desired depth; Negative buoyancy – a rock sinking to the
bottom of a lake, a ship sinking when damaged.
Section 4.12 – How Does Temperature Affect Viscosity and Density? (pages 133 – 135)
1. Fill in the Table 3 by adding increase or decrease to indicate how each property changes with
temperature.
Temperature
Increases
Temperature
Decreases
Table 3
Volume
Increases
Density
Decreases
Decreases
Increases
Viscosity
Decreases
Low viscosity
Increases
High viscosity
Buoyancy
Decreases
Increases
2. Use the terms mass, volume, and density to compare gases, liquids, and solids in terms of the
kinetic molecular theory of matter.
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