density chapter 4 physical science. tuesday, october 2, 2011 supplies: a pencil and science...
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![Page 1: Density Chapter 4 Physical Science. Tuesday, October 2, 2011 Supplies: A pencil and science notebook Standards: 8a) Density is mass per unit volume](https://reader036.vdocuments.site/reader036/viewer/2022062805/5697bfc21a28abf838ca4ce4/html5/thumbnails/1.jpg)
DensityChapter 4
Physical Science
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Tuesday, October 2, 2011
Supplies: A pencil and science notebook
Standards: 8a) Density is mass per unit volume 8b) Calculate the density of substances from
measurements of mass and volume 9f) Apply simple mathematic relationships to
determine a missing quantity
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Warm-up
Given what you know about energy in solids, liquids, and gases, how and why do you think a lava lamp works.
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Agenda
Pass back homework
Density Lecture
Ticket-out
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What is density
Population density?
Forest density?
Density of stars?
Air quality?
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Density in Physics
Density is a property of matter, like color or size.
Density is mass per unit volume.
Given a cubic centimeter of Steel Water Air
Which has more mass?
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Write it
D=m/v
Solve for m
Solve for v
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Solve it
A stainless steel sphere has a mass of 25 grams and a volume of 3.2 cm3. What is the density of the sphere?
A cube has a mass of 7.8 grams. The length of the sides of the cube is 1.2 cm. What is the density of the cube?
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Density is a ratio
Units are g/cm3
Ratio means
1 g/cm3 = 1000 kg/m3
Steel at 8.7 g/cm3 is 8,700 kg/m3 (multiply by 1000 and change units.)
Oak at 600 kg/m3 is 0.60 g/cm3 (divide by 1000 and change units.)
How does the density of oak compare to the density of water?
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Solve it, them compare
Honey’s density is 1.4 g/cm3
Write this as kg/m3
Sandstone’s density is 20,280 kg/m3
Write this as g/cm3
Compare answers with with someone nearby.
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Density Samples
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Determining Density
Use a balance to find the mass
Use a graduated cylinder to find the volume (not a beaker – why?)
D = mass/volume
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Using a graduated cylinder
Read the mark at eye level
Read volume at center of meniscus (ask your teacher!)
1 mL = 1 cm3
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Volume of solids
Length X width X heights gives cubic centimeters
What is the volume of a box that is 10” long, 5” wide, and 3” high?
What is the volume of a box that is 2’ long, 1’ wide, and 9” high?
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More volumes, use 3.14 for π
Sphere: V=(4/3)πr3
What is the volume of a sphere with a radius of 2 cm?
Cylinder: V=πr3h
What is the volume of a cylinder that is 10 cm tall and has a radius of 3 cm?
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Irregular shapes
Volume by displacement of fluid
Remember: 1 mL = 1 cm3
Fill graduates cylinder with fluid to known level (50 mL)
Carefully slide object down the side of the cylinder
Compute the increase in the fluid height
82 mL - 50 mL = 32 mL
32 mL = 32 cm3
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Compute this
I fill a graduated cylinder with 50 mL of water.
I slip a stone into the cylinder and the water raises to 62 mL.
What is the volume of the stone?
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Why density varies
Mass of each atom or molecule that that makes up the substance – a calcium atom has more ‘stuff’ in it than an oxygen atom.
How tightly the atoms are packed -- the atoms are closer together in diamond that in graphite, but both are carbon.
(Except for water) solids are more dense than liquids
Liquids are more dense than gases
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Ticket Out: Answer this
Which has more mass, a pound of bricks or a pound of feathers?
Which is more dense, a pound of bricks or a pound of feathers.