1. Chapter 2 Measurements 2.8 Density
Learning Goal Calculate the density of a substance; use the density to calculate the mass or volume of a substance.
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2. compares the mass of an object to its volume
Density
Density
compares the mass of an object to its volume
is the mass of a substance divided by its volume
is defined as
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3. higher densities contain particles that are closely packed together
Density
Substances that have
higher densities contain particles that are closely packed together
lower densities contain particles that are farther apart
Metals such as gold and lead have higher densities because their atoms are packed closely together.
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4. The density of a solid or liquid is usually given in
Density, Units
In the metric system, densities of solids, liquids, and gases are expressed with different units.
The density of a solid or liquid is usually given in
grams per cubic centimeter (g/cm3)
grams per milliliter (g/mL)
The density of a gas is usually given in grams per liter (g/L).
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5. Density of Common Substances
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6. Guide to Calculating Density
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7. Learning Check
Osmium is a very dense metal. What is its density, in g/cm3, if 50.0 g of osmium has a volume of 2.22 cm3?
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8. Step 2 Plan Write the density expression.
Solution
Osmium is a very dense metal. What is its density, in g/cm3, if 50.0 g of osmium has a volume of 2.22 cm3?
Step 1 Given g; cm3
Need density, in g/cm3
Step 2 Plan Write the density expression.
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9. Step 4 Set up problem, calculate.
Solution
Osmium is a very dense metal. What is its density, in g/cm3, if 50.0 g of osmium has a volume of 2.22 cm3? Step 3 Express mass in grams and volume in cm3.
mass = 50.0 g volume = 2.22 cm3
Step 4 Set up problem, calculate.
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10. Link to the Environment
The oil pumped out of the ground is called crude oil, or petroleum. It is mostly made of hydrocarbons, or compounds that contain only carbon and hydrogen.
In April 2010, an oil rig in the Gulf of Mexico exploded, causing the largest oil spill in U.S. history.
It leaked a maximum of 10 million liters a day into the Gulf of Mexico.
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11. Link to the Environment
Because the density of this oil, 0.8 g/mL, was less than that of water, which is 1.00 g/mL, it floated on the surface, spreading a thin layer of oil over a very large surface.
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12. The density of a solid is calculated from its mass and volume.
Density of Solids
The density of a solid is calculated from its mass and volume.
When a solid is submerged, it displaces a volume of water equal to the volume of the solid.
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13. Density of Solids
In the figure below, the water level rises from 35.5 mL to 45.0 mL after the zinc object is added.
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14. Learning Check
Scuba divers use lead weights to counteract their buoyancy in water. What is the density of a lead weight that has a mass of 226 g and displaces 20.0 cm3 of water when submerged?
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15. Need density (g/cm3) of lead
Solution
What is the density of a lead weight that has a mass of 226 g and displaces 20.0 cm3 of water when submerged?
Step 1 Given 226 g lead
20.0 cm3 water displaced
Need density (g/cm3) of lead
Step 2 Plan. Write the density expression.
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16. Step 3 Express mass in grams and volume in cm3.
Solution
What is the density of a lead weight that has a mass of 226 g and displaces 20.0 cm3 of water when submerged?
Step 3 Express mass in grams and volume
in cm3.
mass of lead weight = 226 g
volume of water displaced = 20.0 cm3
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17. Step 4 Set up problem, calculate.
Solution
What is the density of a lead weight that has a mass of 226 g and displaces 20.0 cm3 of water when submerged?
Step 4 Set up problem, calculate.
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18. Density as a Conversion Factor
Density can be used as a conversion factor between a substance’s mass and volume.
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19. Learning Check
If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt?
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20. Solution
If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt?
Step 1 Given qt milk
density of milk is 1.04 g/mL
Need grams of milk
Step 2 Write a plan.
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21. Step 3 Write equalities, conversion factors.
Solution
If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt?
Step 3 Write equalities, conversion factors.
1 L = qt L = 1000 mL
1.04 g = 1 mL
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22. Step 4 Set up problem, calculate.
Solution
If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt?
Step 4 Set up problem, calculate.
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23. Concept Map
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