1. Density

2. Story of Archimedes
Archimedes was a wise man who lived in ancient Greece. One day Archimedes was approached by the King to determine if the King’s crown was really made of gold. The king feared that he had been swindled and that the crown was made of some cheaper metal that just looked like gold.
Archimedes knew the density of gold. He also knew how much the crown weighed. He needed to find the volume of the crown. This would allow him to determine the density of the metal in the crown. Only then could he compare the density of the crown to that of gold. But, alas, the crown had a very irregular shape which made it impossible to measure with a ruler. He feared that he could not solve the King’s problem and would be banned from society.

3. Story of Archimedes
That night upon arriving home, Archimedes decided to take a bath. Upon getting into his bathtub, he noticed that as he sank into the tub, the level of the water rose. He then realized that if he could measure the amount of water that his body displaced, he could find the volume of his body.
He was so excited with his water displacement discovery, that he jumped out of the bathtub and ran down the street. As he did so he shouted, “Eureka, Eureka!”
Archimedes knew that he could apply his idea to accurately determine the volume of the King’s crown. Then with both the mass and volume of the crown he could determine the density. The King’s problem was solved!
Do you think the crown was real gold?

4. Density Mass Volume Density = Units: g/mL or g/L
Density is an intensive property of matter. This means that no matter how much or how little of a material you have the density will remain the same.
Mass and Volume are both extensive properties of matter. They depend on the amount of material
mass = amount of matter.
Volume = amount of space an object occupies.

5. Example Problems Using the Density Equation
Ex 1: A sample of Fe has a mass of 2.55g and a volume of 0.324mL. What is the density ? m V
2.55g
0.324mL
d = =
= 7.87g/mL

6. Ex 2: The density of Pb is 11. 4g/mL. What is the volume of 1
Ex 2: The density of Pb is 11.4g/mL. What is the volume of 1.20x103g of Pb?
V =
Mass
density
1.20x103g
11.4g/mL =
105 mL

7. Ex 3: Limestone has a density of 2. 72 g/cm3. What is the mass of 24
Ex 3: Limestone has a density of 2.72 g/cm3. What is the mass of 24.9 cm3 of limestone?
m =
d x V =
2.72 g/cm3 x 24.9 cm3
= 67.7 g

8. How do you find the density of a solid object?
Find mass on balance
(object shape does not matter)
Find volume
Regular object measure with a meter stick (V=lwh)
Irregular object measure by water displacement (remember Archimedes)
V = water level with object - water level without object
Calculate density
Divide mass by volume
Eureka, you have done it!