Topic 4-6 Test Review – Grade 8
How is the thickness or a thinness of a fluid measured and what is it called? (p. 40)
The thickness or thinness of a fluid is measured by calculating the FLOW RATE; it is called VISCOSITY
Describe some practical applications (i.e. Industries like Food, Cosmetics, etc.) of viscosity. (p.45)
Viscosity is very important for industries such as:
1) Make-up – want the viscosity of products to be “normal.” Example: Lipstick…want it to be solid and smooth, not runny and misshapen
2) Food Industry – want food to be the proper viscosity. Example: Ice-cream…want it to be cold and thick, not runny and warm.
How is viscosity in different fluids affected by temperature? (p. 48-49)
LIQUIDS: As a liquid is heated, it’s viscosity decreases, as it is cooled, it’s viscosity increases.
GASES: As a gas is heated, it’s viscosity increases, as it is cooled, it’s viscosity decreases.
Calculate density using a formula. (p.57)
REMEMBER!!!! Show your formula and the units please J
# 1: A box has the measurements 1.0cm x 2.0cm x 3.0cm. It has a mass of 350g. What is it’s density?
· V = 6 cm3
· M = 350g
· D = M / V
D = 350 / 6
· D = 58.33 g / cm3
# 2: Aluminum has a density of 2.7g/cm3. What is the volume of an aluminum cube that has a mass of 49g?
· V = ?
· M = 49g
· D = 2.7g/ cm3
V = M / D
· V = 49 / 2.7g/ cm3
· V = 18.15 cm3
# 3: Lead has a density of 11.3 g/cm3. What is the mass of a piece of lead that has a volume of 110cm3?
· M = ?
· V= 110cm3
· D = 11.3 g/cm3
M = D * V
· M = 11.3 g/cm3 * 110cm3
· M = 1243.0 g
What is the relationship between mass and volume when determining density?
To find the density of any object or liquid, you MUST know the mass and the volume. By dividing the mass by the volume, you are able to calculate density.
Describe the density of solids liquids and gases, using the particle model. (p.51)
SOLIDS: Are the most dense of any state. Their particles are extremely crowded together with hardly any space between them.
LIQUIDS: Are less dense than Solids, but more dense than gases. The particles in liquids are sort-of crowded, but are able to slide past one another.
GASES: Are the least dense of any state. The particles are spread out and can easily move past one another. Much space exists between the particles in a gas.
Why can solids support objects more easily than fluids can?
Because solids are so dense (when compared to liquids and gases), their high densities prevent other objects from “sinking” into them. Example – Molasses can be considered a dense liquid, when lighter objects such as paper or cardboard are put on top of molasses, they tend to stay on the surface as the density of molasses prevents them from sinking downwards.
What is buoyancy?
The ability or tendency to float in water or air or some other fluid
If the buoyant force is less than the weight of an object immersed in a fluid…what will happen to that object?
The object will sink into the fluid
Describe 2 ways that would allow a ship (made out of steel) to float.
1) It can spread out it’s volume by increasing the surface area
2) It can include more air within (i.e. large amounts of air fill the hull of a ship)
What is average density and what benefits does it have?
Average density means that an object has become virtually less dense than the fluid it is submerged in (even though the object technically might have a higher density than water)
What is an “Air Bladder” in fish, and what does it have to do with Average Density?
The air bladder in fish contains a mixture of air and water
The fish’s depth in the water depends on how much air is inside the sac.
¡ The more water in the sac the lower the fish sinks.
¡ The more air in the sac the higher the fish rises.
Who was Archimedes, and in 1-2 sentences, explain what he did to come up with “Archimedes Principle”
A long time ago a Greek scientist named Archimedes discovered an important scientific law related to buoyancy. It can be expressed as ‘Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.’
Mrs. Carrick preformed an experiment to determine the density of a button. She obtained the following measurements:
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Calculate the flow rate of the following liquids:
A) Volume = 30 mL, Time = 15 seconds
Flow Rate = 30 mL / 15 seconds = 2 mL/second
B) Volume = 45 mL, Time = 18 seconds
Flow Rate = 45 mL / 18 seconds = 2.5 mL/second
Which of the liquids was more viscous? How do you know?
Liquid A is more viscous (thick) because in one second, you could only get 2 mL of liquid to flow. Liquid B is thinner (less viscous) because in one second you get more liquid to flow, 2.5mL to be exact!
Fill in the blank concerning the viscosity of GASES and LIQUIDS
A) When a liquid is HEATED, its viscosity ___DECREASES_____ (Increases/Decreases). When a liquid is COOLED, its viscosity __INCREASES_____ (Increases/Decreases)
WHY DOES IT DO THAT? (Please take about the particles in liquids gaining or losing energy)
As a liquid heats up, its particles move farther apart from one another, creating fewer interactions between particles and more spaces to exist. This causes the viscosity to decrease.
REAL LIFE EXAMPLE of a liquid who’s viscosity changes with heating or cooling:__MOLASSES or SYRUP
B) When a gas is HEATED, its viscosity __INCREASES_____ (Increases/Decreases). When a gas is COOLED, its viscosity ___DECREASES______(Increases/Decreases)
WHY DOES IT DO THAT? (Please take about the particles in liquids gaining or losing energy)
As gas particles heat up, more energy (from the heat) cause the gas particles to become more excited and move around more. The gas particles begin to collide more and more, cause the gas to become “thicker” or more viscous.
REAL LIFE EXAMPLE of a gas who’s viscosity changes with heating or cooling:__Oxygen
EXTRA PRACTICE
1) What is the volume of a tank that can hold 18 754 Kg of methanol whose density is
0.788g/cm3?
v = 2.38 x 107 cm3
2) What is the density of a board whose dimensions are 5.54 cm x 10.6 cm X 199 cm and
whose mass is 28.6 Kg?
D = 2.45 g
cm3
3) CaCl2 is used as a de-icer on roads in the winter. It has a density of 2.50 g/cm3. What is the
mass of 15.0 L this substance?
m = 3.75 x 104 g
4) In the Macy's Thanksgiving day parade, 2000, there was a new float, the Cheerios' bee,
Buzzbee. The jar of honey it was holding contained 36,763 L of helium. The honey jar was
1/10 of the body size.
What is the volume of the entire float? If the density of helium is 0.000178 g/cm3, what is the
mass of the helium for the entire float in Kg?
v = 367,630 L He
m = 65.4 Kg
5) My gas tank in my car has a total volume of 68 L. The manual says the gas gauge light will
come on when there are only 5 L remaining in the tank and that the car will not be able to
draw on the last 2 L in the tank. Practically speaking, what is the functional volume of the gas
tank? If I ran out of gas, the car won't go, and I put in 5 L of gas, what is the total volume of
gas in my tank? If 5 L of gas has a mass of 450 Kg, what is the mass of the gas in my tank?
What is the density of the gas?
D = m/v
functional volume of tank is 68L - 2 L = 66 L gas
"empty tank" + 5 L = 7 L gas
m = 630 Kg
D = 9.0 x 101 g
cm3
6) The density of paper is 1.20 g/cm3. What is the mass of the paper in a notebook that is 76
mm thick, 215.9 mm wide, and 279.4mm long? Express your answer in significant
digits.
5.5 x 103 g
7) In pottery class, you throw a pot from a lump of wet clay. Your pot's mass is 5.5 Kg. After
the pot is fired, it's mass is 4.9 Kg. The density of wet clay is 1.60 g/cm3 and the density of
fired clay is 1.36 g/cm3. What was the volume of your pot before it was fired? What was
the volume of the pot after it was fired? Express your answer in significant digits.
volume of wet clay is 3.4 x 103 cm3
volume of dry clay is 3.6 x 103 cm3
8) The Italian government is giving Michelangelo's David a bath. In the newspaper, there was a
photo of a person working on the statue. Their hand was half the size of the statue's hand.
If the statue is 4.9m3 and the density of marble is 2.76 g/cm3 what is the mass? Express your
answer in significant digits.
mass of marble = 1.4 x 107 g
9) The volume of the aquarium in our classroom is 1890 L. The density of seawater is
1.03g/cm3. What is the mass of the water in our tank? Express your answer in significant
digits.
mass = 1.95 x 106 g
10) Spanish mahogany is a red, lustrous wood. It is prized over Honduras mahogany, which
does have the characteristic red color and similar grain, but is the wood is not as compact
and has a looser appearance than the Spanish mahogany. A hope chest made of Honduras
mahogany has a volume of .648 m3 and a mass of 349 Kg. An identical hope chest made
of Spanish mahogany has a mass of 550.8 Kg. What is the density of Honduras
mahogany? What is the density of Spanish mahogany? Express your answer in significant
digits.
density of Honduras mahogany is 0.539 g/cm3
density of Spanish mahogany is 0.850 g/cm3