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General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 1
Chemistry and
Measurements
1.10
Density
© 2013 Pearson Education, Inc.
Lectures
Density
Density
 compares the mass of an object to its volume.
 is the mass of a substance divided by its volume.
 are measured in g/L for gases.
 are measured in g/cm3 or g/mL for solids and liquids.
Density expression:
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
2
Densities of Common Substances
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
3
Density Calculations
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
4
Calculating Density
If a 0.258-g sample of HDL has a volume of 0.215 cm3,
what is the density, in g/cm3, of the HDL sample?
Step 1 State the given and needed quantities.
Analyze the Problem.
Given
Need
0.258 g HDL
density in g/cm3 of HDL
0.215 cm3 HDL
Step 2 Write the density expression.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
5
Calculating Density
If a 0.258-g sample of HDL has a volume of 0.215 cm3,
what is the density, in g/cm3, of the HDL sample?
Step 3 Express mass in grams and volume in
milliliters (mL) or cm3.
Step 4 Substitute mass and volume into the density
expression and calculate the density.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
6
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?
A. 2.25 g/cm3
B. 22.5 g/cm3
C. 111 g/cm3
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
7
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 State the given and needed quantities.
Analyze the Problem
Given
50.0 g osmium
2.22 cm3
Need
density g/cm3
Step 2 Write the density expression.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
8
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.
Step 4 Substitute into the density expression.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
9
Measuring Density of Solids
Volume displacement is
the volume of a solid
calculated from the volume
of water displaced when it
is submerged.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
10
Measuring Density
Measure the mass of the solid
before submerging it in water to
determine its volume.
The density of this zinc object is
calculated from its mass and
volume.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
11
Learning Check
What is the density (g/cm3) of 48.0 g of a metal if the
level of water in a graduated cylinder rises from 25.0
mL to 33.0 mL after the metal is added?
A. 0.17 g/cm3
B. 6.0 g/cm3
C. 380 g/cm3
33.0 mL
25.0 mL
object
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
12
Solution
What is the density (g/cm3) of 48.0 g of a metal if the level
of water in a graduated cylinder rises from 25.0 mL to 33.0
mL after the metal is added?
Step 1 State the given and needed quantities.
Analyze the Problem.
Step 2
© 2013 Pearson Education, Inc.
Write the density expression.
Chapter 1, Section 10
13
Solution
What is the density (g/cm3) of 48.0 g of a metal if the level
of water in a graduated cylinder rises from 25.0 mL to 33.0
mL after the metal is added?
Step 3 Express mass in grams and volume in cm3.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
14
Solution
What is the density (g/cm3) of 48.0 g of a metal if the level
of water in a graduated cylinder rises from 25.0 mL to 33.0
mL after the metal is added?
Step 4
Substitute mass and volume into density
expression.
Answer: B
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
15
Sink or Float
Ice floats in water because the density of ice is less than
the density of water.
Aluminum sinks in water because its density is greater
than the density of water.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
16
Problem Solving using Density
Density can be written as a conversion factor.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
17
Problem Solving using Density
Density can be used as a conversion factor.
A density of 3.8 g/mL, can be written as an equality,
or written as conversion factors.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
18
Problem: Density as a Conversion
Factor
If the density of milk is 1.04 g/mL, how many grams of
milk are in 0.50 qt of milk?
Step 1 State the given and needed quantities.
Analyze the Problem.
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Chapter 1, Section 10
19
Problem: Density as a Conversion
Factor
If the density of milk is 1.04 g/mL, how many grams of
milk are in 0.50 qt of milk?
Step 2 Write a plan to calculate needed quantity.
volume US–Metric
factor
density
factor
mass
Step 3 Write equalities and conversion factors.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
20
Problem: Density as a
Conversion Factor
If the density of milk is 1.04 g/mL, how many grams of
milk are in 0.50 qt of milk?
Step 4 Set up the problem to calculate the needed
quantity.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
21
Learning Check
The density of octane, a component of gasoline, is
0.702 g/mL. What is the mass, in kg, of 875 mL of
octane?
A. 0.614 kg
B. 614 kg
C. 1.25 kg
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
22
Solution
The density of octane, a component of gasoline, is
0.702 g/mL. What is the mass, in kg, of 875 mL of octane?
Step 1 State the given and needed quantities.
Analyze the Problem
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
23
Solution
The density of octane, a component of gasoline, is 0.702
g/mL. What is the mass, in kg, of 875 mL of octane?
Step 2 Write a plan to convert the given unit to the
needed unit.
Density
mL Factor
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Metric
Factor
Chapter 1, Section 10
kg
24
Solution
The density of octane, a component of gasoline, is 0.702
g/mL. What is the mass, in kg, of 875 mL of octane?
Step 3 State the equalities and conversion factors.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
25
Solution
The density of octane, a component of gasoline, is 0.702
g/mL. What is the mass, in kg, of 875 mL of octane?
Step 4 Set up the problem to cancel units and
calculate the answer.
Answer: B
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
26
Specific Gravity
Specific Gravity (sp gr)
 is the relationship between the density of a
substance and the density of water.
 is determined by dividing the density of the sample
by the density of water.
 is a unitless quantity.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
27
Specific Gravity
Specific Gravity is measured by an instrument called
a hydrometer.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
28
Learning Check
Which of the following samples of metals will displace
the greatest volume of water?
A
25 g of aluminum
2.70 g/mL
© 2013 Pearson Education, Inc.
B
45 g of gold
19.3 g/mL
Chapter 1, Section 10
C
75 g of lead
11.3 g/mL
29
Solution
The correct answer is A.
25 g of aluminum
2.70 g/mL
Plan: Calculate the volume for each metal, and
select the metal sample with the greatest volume.
© 2013 Pearson Education, Inc.
Chapter 1, Section 10
30