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. © 2014 Pearson Education, Inc.

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 © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

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). © 2014 Pearson Education, Inc.

Density of Common Substances © 2014 Pearson Education, Inc.

Guide to Calculating Density © 2014 Pearson Education, Inc.

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? © 2014 Pearson Education, Inc.

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 50.0 g; 2.22 cm3 Need density, in g/cm3 Step 2 Plan Write the density expression. © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

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? © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

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 © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

Density as a Conversion Factor Density can be used as a conversion factor between a substance’s mass and volume. © 2014 Pearson Education, Inc.

Learning Check If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt? © 2014 Pearson Education, Inc.

Solution If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt? Step 1 Given 0.50 qt milk density of milk is 1.04 g/mL Need grams of milk Step 2 Write a plan. © 2014 Pearson Education, Inc.

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 = 1.057 qt 1 L = 1000 mL 1.04 g = 1 mL © 2014 Pearson Education, Inc.

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. © 2014 Pearson Education, Inc.

Concept Map © 2014 Pearson Education, Inc.