1. What is Density

2. What does it mean to be dense?
Example: Think about Population Density.
Two Countries have the same number of people living them.
Which one is more densely populated?

3. Country “A” vs. Country “B”

4. What does it mean to be dense?
Example:
Two Countries are the exact same size.
Which one is more densely populated?

5. Country “A” vs. Country “B”

6. Population Density vs. Density
Population Density is a measure of the amount of people in an amount of land.
Density is a measure of the amount of matter in an amount of space.

7. Density is a Derived Unit Which means it is:
A Calculated measurement (NOT a Pure measurement) that depends on…
The amount of matter in an object, which is called MASS.
The Amount of Space occupied by an object, which is called VOLUME.

8. So what is density?
A material's density is defined as its mass per unit volume.
It is, essentially, a measurement of how much mass would be in EACH cm3 or ml of the object.

9. The object to the below has a MASS of 8.25 ounces
Now remove the RED block from the object.
The object to the right has a VOLUME of 11 Blocks
That means the DENSITY of the object is 0.75 ounces per block
What’s the MASS of the RED block?
What if we took a BLUE one instead? What would be the MASS of the BLUE block?
0.75 ounces
0.75 ounces

10. Every object around us is made of Molecules.
Different types of molecules can have different masses and different sizes
There is little or no space between the molecules of objects. (The molecules are always touching)
By changing the number or type of molecules in an object you can change the density of the object.

11. Imagine that a Beach ball represents a molecule
Imagine that a Beach ball represents a molecule. The size of the beach ball can change depending on how much force is applied to it.
To understand what is happening inside an object: imagine that we fill the entire classroom with beach balls (from wall to wall – floor to ceiling)
Is it possible to make this “object” more dense by adding another beach ball?

12. YES. Since the walls give a little, we can force one or two more beach balls into the same space. This is also true of molecules
Is there another way to make this more dense?

13. To calculate Density:
MASS of the Object
D =
Volume of the Object

14. Notice that neither label will cancel out. So both must be kept.
To calculate Density:
Example:
1) Mass = 4.50 g
2) Volume = 80.0 ml
STEP 1 = Mass
Volume
Notice that neither label will cancel out. So both must be kept.
4.50 g
Step 2 = =
0.056 g/ml
80.0 ml

15. 1 ml of Liquid will fit into a cube 1cm x 1cm x 1cm (1 ml = 1 cm3)
Density’s Label
Mass is always measured in grams
Volume of Liquids and Gases are measured in Milliliters
Volume of Solids are measured in cm3
This means:
1 ml of Liquid will fit into a cube 1cm x 1cm x 1cm (1 ml = 1 cm3)

16. Density’s Label Density of Liquids or Gases: g/ml Density of Solids:
g/cm3

17. Use the Scale How to measure Mass?
For Liquids and Gases you will need to subtract the mass of the container

18. How to measure Volume? Cubes: V = L x W x H Cylinders: V = x r2 x H π
Liquids:
Use the GRADUATED CYLINDER.
Solids:
Use Displacement (Direct or Overflow)
Use volume formulas
Cubes: V = L x W x H
Cylinders: V = x r2 x H π

19. Example 1 What is the Density of the following Solid Object? MASScm
MASS g
W = 2.00 cm
L = 2.45 cm

20. Answer (Example #1) V = 13.48 cm3 M d = = = 11.13 g/cm3 V
STEP ONE
Mass = g
Volume = L x W x H
STEP TWO
V =
(2.45 cm) x
(2.00 cm) x
(2.75 cm)
STEP THREE
V = cm3 g M
d = =
= g/cm3 V
13.48 cm3

21. Example 2
What is the Density of the following Solid Object?
D = 6.00 cm
H = 8.00 cm
r = ½ of D
MASS
175 g

22. Answer (Example #2) V = 226.08 cm3 M d = = = 0.774 g/cm3 V
STEP ONE
Mass = 175 g
Volume = π x r2 x H
STEP TWO
V =
(3.14)x
(3.00) x cm
(3.00) x cm
(8.00) cm
STEP THREE
V = cm3
175 g M
d = =
= g/cm3 V
cm3

23. Example 3 What is the Density of the following Irregular Object?
MASS of Object = g
Volume of Overflowed H2O = 22.7 ml

24. Answer (Example #3) V = 22.7 cm3 M d = = = 2.38 g/cm3 V Mass = 54.00 g
Volume = Volume of Overflowed H2O
One ml = One cm3
Since the OBJECT is SOLID use this Label
V = 22.7 cm3
54.00 g M
d = =
= 2.38 g/cm3 V
22.7 cm3

25. Volume of Displaced H2O = 5.0 ml
Example 4
What is the Density of the following Irregular Object?
MASS of Object = 8.25 g
Volume of Displaced H2O = 5.0 ml
Volume Before =
7.5 ml
Volume After =
12.5 ml

26. Answer (Example #4) V = 5.0 cm3 M d = = = 1.65 g/cm3 V Mass = 8.25 g
Volume = Volume of Displaced H2O
One ml = One cm3
Since the OBJECT is SOLID use this Label
V = 5.0 cm3
8.25 g M
d = =
= 1.65 g/cm3 V
5.0 cm3