Lesson 1 -
(2-3)
1. density - the mass of a known volume of a
substance; measured in g/cm3
2. mass - the amount of matter in an object; measured
in g or kg.
3. volume - the amount of space occupied by matter;
measured in L, mL, cm3, or m3.
DENSITY
Read the article titled “Archimedes' Crowning
Moment” on page 20 in the Properties of Matter
lab workbook.
Archimedes
(287 - 212 B.C.)
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
•
•
The mass and volume of
matter determine its
density.
Density affects buoyancy.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
How to Determine Density
•
•
•
Density is defined as the ratio of
an object's mass to its volume:
d=m/v
Density is usually expressed as the
number of grams in one cubic
centimeter (cm3)
The density of water at room
temperature is one gram per cubic
centimeter (1 g/cm3).
How to Determine Density
•
•
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This means that every gram of
water has a volume of 1 cm3.
The word per is replaced by the
fraction bar. (1 g/cm3)
The bar tells you that you can
calculate the density of matter by
dividing its mass by its volume.
Sink or Float?
•
•
Objects with densities
greater than water will sink in
water.
Objects with densities less
than water will float in water.
Skittles, Starbursts, and
Gummi Bears … Oh My!
 Students
must find another student
who has the same color/flavor and type
of candy.
 Once students find their match, they
must share three things with each other
that they did not know.
Using Density
•
•
Density is a physical property of
matter.
Since it is rare to find two
different substances with identical
densities, density can be used in
helping scientists identify
materials.
An example to determine
the density of a golf ball.
The greater the mass within a
given volume, the greater the
density. Have you ever held a
gold ring and a silver ring of the
same size?
If you have two objects of
the same size (volume),
the heavier object will
have the greater density.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
Archimedes Principle
Archimedes’ principle states
that a body immersed in a fluid
is buoyed up by a force equal
to the weight of the displaced
fluid.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
Archimedes’ Principle
• A completely submerged object
displaces, or takes the place of, a
volume of fluid equal to its own
volume.
• A partially submerged object
displaces a volume of fluid equal to
the volume of its submerged
portion only.
– This is why a ship made of very
heavy materials is able to float.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
Buoyant Force
• Water and other fluids exert an
upward force on submerged objects
called the buoyant force.
• Buoyant force acts in the direction
opposite of gravity, so it makes the
object feel lighter.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
Density Affects Buoyancy
Objects with higher densities will
sink below those with lower densities.
The density of pure
water is 1 g/cm3.
The density of ice
is .92 g/cm3 and a
brick is 1.84 g/cm3
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
To determine whether a given body
will float in a given fluid, both
weight and volume must be
considered.
That is, the relative density of the
body compared to the fluid
determines the buoyant force.
Discussion on buoyancy
How steel ships float
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
You Can Do This!
Observe how displacement
works using a soda can and
containers of water.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
Different Types of Buoyancy
Positive
• Negative
• Neutral
COS 7 : Describe the states of matter based on kinetic energy
•
of particles in matter.
An object with positive buoyancy
has density which is less than
the surrounding fluid, and will
float in that fluid.
An object with negative
buoyancy has density which is
greater than the surrounding
fluid, and will sink in that fluid.
An object with neutral buoyancy
has equal density to the
surrounding liquid.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
Changing Density
• An object can be made to sink or
float in a fluid by changing its
density.
• If the mass of an object is
decreased while the volume remains
the same, the density will decrease
and the object will float.
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
Submersibles and Buoyancy
Divers and submarines must
alter their density to attain
different kinds of buoyancy so
they can navigate under water.
How might they do that?
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.
COS 7 : Describe the states of matter based on
kinetic energy of particles in matter.
Fish Control Their Own Buoyancy
The swim bladder is a small sac
in the fish’s anterior abdomen
which is responsible for
maintaining buoyancy. When a fish
has Swim Bladder Disease, it can’t
control its buoyancy and will
either sink or float.
Oh
Nooooo!
Lesson 4 29. vacuum - space without matter.
30. **density - the mass of a known volume
of a substance; usually measured in
g/cm3. (m/v)
31. gas - a state or phase of matter in
which a substance has no definite
shape or volume……………
Lesson 4 – Do Gases Have Density
You will determine the mass, volume,
and density of a bottle of air.
Lesson 4 -
Does air have density?
Lesson 4
If air is…… then air has ….. because air has …..
Getting Started
Observe the apparatus that the teacher has set up at
the front of the class room. Watch the
demonstration and discuss what you observed with
your lab group. Complete the following assignment
using complete sentences.
1. Describe what happens when colored water is
poured into each funnel.
2. Explain why water behaves differently in each
funnel.
Getting Started
Observe the syringe apparatus that is being passed
around the class. Complete the following assignment
using complete sentences.
1. Explain what you observe when one syringe is pushed
in and draw a picture of your observations.
2. What do the funneled test tube and syringe
apparatus tell you about air?
Lesson 4
Procedure
Inquiry 4.1
1.What will you need to measure in order to calculate
the density of air?
2. Discuss with your group how to use the materials
provided to find the density of air. Try to agree on a
procedure that you think will work.
3. Write a paragraph explaining your procedure.
Finding the Density of Air
Record the following procedure in your lab report.
1.
2.
3.
4.
5.
6.
Lesson 4
Results
Finding the Density of Air
Volume of
bottle
Mass of bottle, Mass of bottle, Mass of air
washer, &
washer, &
(g)
rubber valve rubber valve
after
(g)
removing air
(g)
Density of air
(m/v)
(g/cm3)
Reflecting On What You've Done
Answer the following questions using complete
sentences.
1. How does the density of air compare with the
density of solids and liquids?
2. Are all the group results the same?
Lesson 4 –
Gases have mass, volume, and density.
Air is less dense than liquids and
solids.
You Can Do This
Use the materials at your work station to make a
Cartesian Diver to demonstrate changes in
density affecting buoyancy. Your model should
allow you to control the sinking and floating of
your diver. Explain how and why your model
allows you to control your diver.
The first team to figure it
out, wins a treat!
COS 7 : Describe the states of matter based on kinetic energy
of particles in matter.