1. Density

2. What is density?
Density is a comparison of how much matter there is in a certain amount of space.

3. Density INTENSIVE property of matter. EXTENSIVE - does NOT depend
Density is an
INTENSIVE property
of matter.
- does NOT depend
on quantity of
matter.
Brick
Styrofoam
Contrast with
EXTENSIVE
- depends on
quantity of matter.
- mass and volume

4. Density M V
D = M
M = D x V
ass D V M D
V =
ensity
olume

5. What is density? Density = mass OR mass ÷ volume. volume
Units for density: g/cm3 or g/mL or g/L
(solids) (liquids) (gas)
ALWAYS REMEMBER UNITS!

6. Mass Mass is the amount of matter an object contains
We find mass by using a balance
Mass is usually measured in grams (g)

7. Volume Volume: the amount of space an object occupies
Volume of a regular solid (squares and rectangles):
length x width x height
cm x cm x cm = cm3
Metric Units for volume
1 liter (L) = 1000 milliliters (mL)
1 milliliter (mL) = 1 cm3 (or ft3) = 1 gram*

8. Volume cont. Volume of an irregular solid (like a rock)
Water Displacement Method
Subtract (final volume – initial volume) to find the volume of the object
How could we do this??
The volume can be expressed in cm3 since 1mL of water = 1 cm3
Volume of a liquid
Measured using a graduated cylinder

9. Measuring Volume
We will be using graduated cylinders to find the volume of liquids and other objects. WHY?
Read the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water.
What is the volume of water in the cylinder? _____mL
What causes the meniscus?
A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides.
Top Image: Bottom Image:

10. Measuring Liquid Volume
What is the volume of water in each cylinder?
Images created at A B C
Pay attention to the scales for each cylinder.

11. Liquid Layers
Check out this picture. Which layer has the highest density?
Which layer has the lowest density?
Imagine that the liquids have the following densities:
10g/cm3. 3g/cm3.
6g/cm3. 5g/cm3.
Which number would go with which layer?

12. Liquid Layers – Try with your neighbor
Which liquid has the highest density?
Which liquid has the lowest density?
Which liquid has the middle density?

13. Consider Equal Volumes
Mass
Density =
Volume
Equal volumes…
…but unequal masses
The more massive object
(the gold cube) has the
_________ density.
Question: Which weighs more a ton of feathers or a ton of bricks?
(They weigh the same)
Question: Which occupies a larger volume; a ton of feathers or a ton of bricks?
(the feathers will occupy a larger volume)
GREATER
aluminum
gold
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 71

14. Consider Equal Masses Equal masses… …but unequal volumes.
The object with the
larger volume
(aluminum cube) has
the smaller density.
gold
aluminum
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 71

15. Density V = 825 cm3 M = DV D = 13.6 g/cm3 M = (13.6 g/cm3)(825cm3)
An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass.
GIVEN:
V = 825 cm3
D = 13.6 g/cm3
M = ?
WORK:
M = DV
M = (13.6 g/cm3)(825cm3)
M = 11,200 g

16. Density D = 0.87 g/mL V = M V = ? M = 25 g V = 25 g 0.87 g/mL
A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid?
GIVEN:
D = 0.87 g/mL
V = ?
M = 25 g
WORK:
V = M D
V = g
0.87 g/mL
V = 29 mL