2. NOTES—WHAT IS DENSITY?
Density is the amount of mass per unit of volume; it describes how much matter is packed into a space.
Density is determined by its mass and volume

3. NOTES—WHAT IS DENSITY? Density is a characteristic property of matter
A characteristic property does not depend on size (it will not change even if the amount of matter changes); therefore density is not dependent on the shape or amount of the substance
1mL of water has a density of 1g/mL
1000 mL of water has a density of 1 g/mL
It is used to help identify one type of matter from another.
The density of a pure substance is constant (at same temperature and pressure); it never changes.

4. CALCULATING DENSITY You need to measure an object’s mass and volume
Density is calculated using the formula:
Density = mass (g) ÷ Volume (mL or cm3)
The basic unit for density is g/mL (liquid) or g/cm3 (solid or gas)
D= m v

5. CALCULATING DENSITY
When solving math problems, always show all work (even when using a calculator)
STEPS:
Write the formula
Substitute measurements into formula
Solve, label units and circle

6. Calculating density practice MUST SHOW WORK-DO ON LEFT SIDE OF NOTEBOOK
Mass (g)
Volume (cm3)
Density (g/cm3 or g/mL)
200
200 mL
500
10 cm3
700
1000 mL

7. Why do substances either float
or sink in a fluid?
First, compare the density of the object/substance to the fluid it is in.
If an object/substance is more dense than the fluid, it will sink
If an object/substance is less dense than the fluid, it will float
If an object/substance’s density is the same as the fluid, it won’t sink or float to the top; it will move toward the center of the fluid (neutral buoyancy)

8. How can you tell if something will float or sink in a fluid?
The density of water is 1 g/mL.
Do you know why ice floats on water?
The density of ice is .92 g/cm3
For example:
certain types of wood have a density of .8 g/cm3, so they will float in water.
Steel has a density of 7.8 g/cm3, so it will sink in water.
See it in action:

9. Ships and boats are often made of steel. Why do they float on water?

10. How is density of matter effected by heat energy?
As temperature increases, so does the amount of energy
In general, the more energy a substance has:
The more space between its molecules
The less dense it is
That’s why…
Solids are usually the most dense phase of matter
The molecules are tightly packed.
Solids have little energy

11. How is density of matter effected by heat energy, continued?
liquids are less dense than solids
There is more space between the molecules
liquids have more energy than solids
An exception to the rule: Ice (H2O) is less dense than liquid water. Do you know why?
Gases are the least dense state of matter
There is lots of space between the molecules
Gases have more energy than any phase

12. Does the density of a substance change if the amount changes?
The density of a pure substance does not change if the size or amount changes
For example:
Find the density of a wooden block
if mass=8g and
volume= 10cm3
Density= ______
If the block is cut in half
Mass=
Volume=
Density =
Did the density change?
No, because the ratio of mass to volume is all relative

13. STATES OF MATTER AND DENSITY

14. NOTES—WHAT IS DENSITY? Most dense least dense
The more space between the atoms, the less dense the substance is.
In general,
solids are more dense than liquids
liquids are much more dense than
gases, but less dense than solids
gases are the least dense of all