Lorraine – You Are
My…
DENSITY
Density is…
In general – the
amount of stuff in a
given area.
Think population
density
Oklahoma New York
Density
For science… density is equal to the
mass of a thing divided by its volume.
What are mass & volume again?
Mass – amount of matter – measured in
grams (g)
Volume – amount of space something
occupies – measured in cm3 or mL
r=m/v the units for density are g/cm3
(or g/mL for later discussion…..)
Volume
For the easy objects
(length)x(width)x(height)
l x w x h ~ (cm)x (cm)x (cm)=cm3
What about cylinders and cones?
What can we do for the not so easy
objects????
Here is a clue - displacement
Quick density lab
Hypothesize – rank the four
pieces of metal by density –
highest to lowest
Find the density of each
What do you notice???
What is density good for???
Back to odd shapes…
Archimedes?? Do you know him?
Was in his bath tub one morning – he noticed
that as his body went in to the water – the
water rose out of the way. He realized that
the volume of H2O that rose was equal to the
volume of his body.
Legend has it that he ran down the streets of
Greece stark naked yelling “Eureka”. –
meaning – OMG I’ve Got It.
Eureka…
The volume of an object is equal to the
volume of H2O it displaces!
The implications of this discovery were
huge.
After further testing – Archimedes
discovered that 1g H2O = 1mL H2O = 1
cm3 H2O
So - what is the density of water???
So…
If an object has a density 1g/cm3,
what will it do if placed in water?
If an object has a density =1g/cm3,
what will it do if placed in water?
Now then…
If an object has a
density of 6g/cm 3,
and you cut it in half,
what will the density
of each half be?
Intrinsic properties
Intrinsic properties are properties that
can be used to positively identify an
object
Like fingerprints, dental records or DNA for human
ID
Density is an intrinsic property – if you
know the density of a metal – no
matter what size or shape – you can ID
the metal.