What is Density?
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Transcript What is Density?
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What is happening? Why?
Why do these float?
Density
What is density?
Density is a ratio of how much
matter there is in a certain amount
of space.
A measure of how many particles
are packed into a certain area.
More dense = more particles in a space
Less dense = less particles in a space
How do I find density?
I need to find out how much stuff (mass) is in
a certain amount of space (volume)
What instruments do I need?
To find the mass of
an object
Triple Beam
Balance
Units are g
To find the volume
of the object
Ruler or graduated
cylinder
Units are cm3 or mL
How do I calculate density?
Density = mass
OR
volume
mass ÷ volume.
Units for density:
or
g
cm3
g
ml
ALWAYS
REMEMBER
UNITS!
Does the sample size affect the
density of an object?
In other words, if I
break off a piece of
this cube, will it have
a different density
than the whole
piece?
NO!!!
Density is based on total mass
divided by total volume.
When one changes, the other also
changes, so the density (which is
a ratio) stays the same!!!
Which one is more dense?
Which table group is most dense in the
classroom?
How about this: Which square is more dense?
Density of Water
Water has a density of 1g/mL
If an object has a density greater than 1g/mL, it
will sink in water
If an object has a density of less than 1g/mL, it
will float in water.
What do we know about the
density of diet coke vs. coke vs.
water?
Do liquids have different
densities?
Yes! So what happens when you mix
them?
They form layers with the highest density
falling to the bottom.
Alcohol = .80 g/ml
Vegetable Oil = .90 g/ml
Water = 1.0 g/ml
Salt Water = 1.2 g/ml
The density of the liquid
affects how you float too!
Denser liquids help you float more easily.
That is why it is easier to float in the
ocean, than in a freshwater lake.
Illustrating Density
Metals have different densities
Lead 11.3 g/cm3
Aluminum 2.7 g/cm3
These are all over 1.0 g/ml and most ships
are made of metal. So how do boats float?
Explain why one bowling ball
floats and one sinks
http://www.youtube.com/watch?v=NqNGW0oOXE4
Density affects many of Earth’s
processes
Density helps create ocean currents
Density helps move melted rocks
under Earth’s crust
crust
mantle
core
Hot material rises, cooler material sinks,
creating a current, called a Convection
Current
Solid Land has different densities
Continental Plates – lighter, thicker, made of
granite
Oceanic Plates – heavier, thinner, made of
basalt
Convergent Boundary
Plates move toward each other
The more dense oceanic plate subducts under the
less dense continental plate
Normal and Low bone densities
Low density bones break more easily.
Temperature can affect
density
Remember. . . Warm air rises.
So this means warm air is less dense than
cold air and it rises
Density causes your attic to be hot in
the summer