1. DENSITY

2. Density: By definition: How heavy something is compared to its size
In math:
d=m/V
m=mass
V=volume
Example: The density of gold is 19.3 g/mL this means that every 1 mL of gold weighs 19.3 grams.

3. What is volume? Volume: the amount of space an object occupies.
Formula:
Cube = l·w·h
Sphere = 4/3πr3
Cylinder = πr2 * h
How could you determine the volume of an irregular object?
Water displacement

4. Calculating Volume Try this one… Q: What is the volume of the cube?
V = 288 in3
Make sure to correctly label your answer!

5. Things you should know:
Density of water: 1 g/mL
An object will float in water if the density is less than 1 g/mL (ie d=.97 g/mL)
An object will sink in water if the density is greater than 1 g/mL (ie d=1.1 g/mL)

6. Try this one
If this cube has a mass of 36 grams, what is the density of the cube?
Will the cube float?
4 cm
3 cm
6 cm
Volume = 4cm * 6cm * 3cm = 72 cm3
Density = 36 grams / 72 cm3 = 0.5 g/cm3
Yes, it will float.

7. A baseball has a mass of 146 grams. If it has a radius of 3
A baseball has a mass of 146 grams. If it has a radius of 3.5 cm, what is
density of a baseball?
Will a baseball float?
First calculate the volume.
V = 4/3π(3.5cm)3 = 180cm3
Density = 0.81g/cm3
IT FLOATS

8. What about the density of a cylinder?
If the cylinder shown has a mass of 18 grams, what is its density?
Volume = cm3
Density = 0.18 g/cm3
2 cm
8 cm

9. What about with an irregular object?
A rock has a mass of 260 grams. In order to determine its volume it is dropped into a graduated cylinder. The water level changes from 40 mL to 120 mL. What is the density of the rock?
Density = 260g / 80mL = 3.25 g/mL
Will it float?

10. Q: What is the density of the Earth in g/mL?
Mass: 5.98×1024 kg
Volume: 1.08×1024 L
5.98×1024 kg
1000 g =
5.98×1027 g
1 kg
1.08×1024 L
1000 mL =
1.08×1027 mL
1 L
A: 5.98×1027 g/ 1.08×1027 mL ≈ g/mL

11. Try this one…
Q: A block of aluminum occupies a volume of 15.0 mL and weighs 40.5 g. What is its density?
d= 40.5g/15mL
A: d= 2.7 g/mL

12. More Practice
Q: What is the weight of the ethyl alcohol that exactly fills a mL container? The density of ethyl alcohol is g/mL.
Use density as a conversion factor
in dimensional analysis
A: g=158 grams
200.0 mL
0.789 g
1 mL

13. Use dimensional analysis
A chunk of aluminum displaces 4 Liters of water. If the density of aluminum is 2.70 grams/mL, what is the mass in kilograms of the sample?
4 L
1000 mL
2.70 g
1 kg
= 10.8 kg
1 L
1 mL
1000 g

14. One More
Q: A piece of metal has a density of 12.6 kg/L. If you have 25 mL of this metal, how many grams is it?
25 mL
1 L
12.6 kg
1000 g
1000 mL
1 L
1 kg
A: 315 grams

15. THE END
Yay for density…