It’s not just about weight anymore…
Relate the arrangement of subatomic particles
in a substance to its density and observable
macroscopic behavior.
 How
close the atoms or molecules are
to each other
 More than “heaviness” - density
includes how much space an object
takes up!!
 All substances have density including
liquids, solids, and gases
Less dense
More dense
Least ‘compact’ of the phases of matter
 Warm gases are less dense than cold
gases – one reason for how weather
works
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Molecules are close together but can move
past each other
Colder liquids are denser than warm liquids
 water at 50oC (120oF): 0.9880 g/mL
 water at 40oC (104oF): 0.9923 g/mL
 water at 30oC (86oF): 0.9956 g/mL
 water at 20oC (68oF): 0.9982 g/mL
 water at 10oC (50oF): 0.9997 g/mL
Cold water in lakes tend to sink (this
creates a constant mixing of water,
nutrients, and other substances)

The more dissolved solids in a solution, the
more dense
 pure water (0% salt) = 1.00 g/mL
 15% salt water = 1.11 g/mL
 25% salt water = 1.19 g/mL
Color added to show layers
Coffee creamer is denser than coffee

The most ‘compact’ of the phases of matter.
Mercury density = 1.3600 g/cm3
 Lead density = 1.1340 g/cm3

Mercury is a liquid metal at room temperature.
Lead is a solid at room temperature. Pool balls
are made of lead. Would lead sink or float in
mercury?
Why do the bubbles
rise out of the
water?
egg
Solid water (ice)
Liquid water
If you combine phases, you can
get interesting densities:
 Styrofoam (solid plastic with air bubbles
inside): 0.35 g/cm3
 Whipped cream (liquid with air
bubbles): 0.50 g/cm3
Match the substance to its picture above:
•NaCl: 2.16 g/cm3
•fluorine: 0.001696 g/cm3
•helium: 0.0001785 g/cm3
•magnesium: 1.74 g/cm3
•water: 1.00 g/cm3
Least to most dense:
helium: 0.0001785 g/cm3
fluorine: 0.001696 g/cm3
•It’s formula is F2!
water: 1.00 g/cm3
magnesium: 1.74 g/cm3
NaCl: 2.16 g/cm3
Using the mathematical definition of density,
compare the densities of regular and irregular
objects using their masses and volumes.
A BIG Idea: Density is an intensive property. It is built into the
substance due to the compactness of the atoms.
Any size, any shape: aluminum is still 2.70 g/cm 3
If an object’s density is 2.70 g/cm3, it MUST be aluminum
Density is the amount of mass in a space. So,
Density = mass / volume
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Jack has a shiny object. It has a mass of
6.35g and a volume of 2.35 cm3. What is the
density of the object? What is it made of?
Jill has a gel pen. The gel pen has a mass of
8.30g and a volume of 2.00cm3. What is the
density of the pen?
Density is the amount of mass in a space. So,
Density = mass / volume
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Jack has a shiny object. It has a mass of 6.35g
and a volume of 2.35 cm3. What is the density of
the object? What is it made of?
2.70 g/cm3, made of aluminum
Jill has a gel pen. The gel pen has a mass of
8.30g and a volume of 2.00cm3. What is the
density of the pen?
4.15 g/cm3
Try one of the videos on the plan to see how to
determine densities in the lab…..
Then try some Ways to Practice and Extend
Your Learning (also on the plan).