Density Notes
Matter: anything that has mass and
takes up space.
Mass: a measurement of the amount of
matter in an object
SI unit for mass = Kilogram (kg),
mass is measured with a balance
*In class, we’ll use small amounts of
materials so generally mass will be
measured in grams (g).
Volume: a measurement of the amount
of space matter occupies
Derived SI unit = cubic meter (m3),
*In class, we’ll use smaller objects so
the volume of solids is measured in cm3
Fluid (liquids or gases) volume is normally
measured in milliliters (mL), liquid
volume is generally measured in a
graduated cylinder.
Important conversion to remember:
1 cm3 = 1 mL and 1g= 1mL
The volume of regular shaped objects
such as a cube, rectangle, or cylinder can
be calculated using an algebraic formula.
Example:
Volume of a rectangle =
length × width × height (l•w•h)
Irregular shaped objects can be
measured by water displacement.
https://www.youtube.com/watch?v=RoK
Cwl3echA
When an object is immersed in water…it
pushes the water out of the way
(displaces the water).
The amount of displacement = the
volume of the object.
http://www.youtube.com/watch?v=e0geXKxeTn4
So…All matter has mass
and volume…these two measurements
are used to calculate the density of
matter.
Density: the amount of matter within a
given unit of volume.
Density is a basic physical property of all
matter.
We often relate the density of objects to
the density of water. We can easily
observe behavior in water so it is a good
reference point and it’s an easy value to
memorize…Pure water has a density of
1g/cm3 or 1g/mL.
If an object floats on water… density
must be less than 1. Or if it sinks,
density is greater than 1.
To calculate the density of an object you
must have the mass and volume of an
object.
Density = Mass
Volume
D=M
V
Practice Examples:
1. A cup of gold colored metal beads was measured to have a mass of
425 grams. By water displacement, the volume of the beads was calculated to be 48.0
cm3. Given the following densities, identify the metal.
Gold: 19.3 g/mL
Copper: 8.86 g/mL
Bronze: 9.87 g/mL
But wait- I do not see a density measurement. You must use the measurements given to
find it!
You may find your answer is in g/cm3, look back in your notes- what does 1cm3= _____
2. Gasoline is a non-polar liquid that will float on water. 450 grams of gasoline is
spilled into a puddle of water. If the density of gasoline is
0.665 g/mL, what volume of gasoline is spilled?
3. An irregularly shaped stone was lowered into a graduated cylinder holding a volume of
water equal to 20.0mL. The height of the water rose to 30.2mL. If the mass of the stone
was 25.0g, what was its density?
Oh no- we have 2 milliliter measurements- what must we do first?
Remember density of solids is usually measure in g/cm3. How do we go from g/mL to g/cm?
Look back in your notes. **Hint, what does 1mL = ______