Solution
Chapter 2: Measurement and Problem Solving
The SI System
• All units in the SI system are related to the standard unit by a power of 10
• The power of 10 is indicated by a prefix
• The prefixes are always the same, regardless of the standard unit
Prefix megakilodecicentimillimicronano-
Symbol d c m
M k m or mc n
Common Prefixes in the SI System
Decimal
Equivalent
1,000,000
1,000
0.1
0.01
0.001
0.000 001
0.000 000 001
Power of 10
Base x 10 6
Base x 10 3
Base x 10 -1
Base x 10 -2
Base x 10 -3
Base x 10 -6
Base x 10 -9
Length
• = Measure of the two-dimensional distance an object covers
• SI unit = meter
About 3½ inches longer than a yard
• 1 meter = one ten-millionth the distance from the North Pole to the
Equator = distance between marks on standard metal rod in a Paris vault = distance covered by a certain number of wavelengths of a special color of light
• Commonly use centimeters (cm)
1 m = 100 cm
1 cm = 0.01 m = 10 mm
1 inch = 2.54 cm (exactly)
Mass
• = Measure of the amount of matter present in an object
• SI unit = kilogram (kg)
about 2 lbs. 3 oz.
• Commonly measure mass in grams (g) or milligrams
(mg)
1 kg = 2.2046 pounds, 1 lbs. = 453.59 g
1 kg = 1000 g = 10 3 g,
1 g = 1000 mg = 10 3 mg
1 g = 0.001 kg = 10 -3 kg,
1 mg = 0.001 g = 10 -3 g
Volume
• = Measure of the amount of three-dimensional space occupied
• SI unit = cubic meter (m 3 )
a Derived Unit
• Commonly measure solid volume in cubic centimeters (cm 3 )
1 m 3 = 10 6 cm 3
1 cm 3 = 10 -6 m 3 = 0.000001 m 3
• Commonly measure liquid or gas volume in milliliters (mL)
1 L is slightly larger than 1 quart
1 L = 1 dL 3 = 1000 mL = 10 3 mL
1 mL = 0.001 L = 10 -3 L
1 mL = 1 cm 3
Length
Common Units and Their Equivalents
1 kilometer (km) = 0.6214 mile (mi)
1 meter (m) = 39.37 inches (in.)
1 meter (m) = 1.094 yards (yd)
1 foot (ft) = 30.48 centimeters (cm)
1 inch (in.) = 2.54 centimeters (cm) exactly
Mass
1 kilogram (kg) = 2.205 pounds (lb)
1 pound (lb) = 453.59 grams (g)
1 ounce (oz) = 28.35 (g)
Common Units and Their Equivalents
Volume
1 liter (L) = 1000 milliliters (mL)
1 liter (L) = 1000 cubic centimeters (cm 3 )
1 liter (L) = 1.057 quarts (qt)
1 U.S. gallon (gal) = 3.785 liters (L)
Problem Solving and Dimensional Analysis
• Arrange conversion factors so starting unit cancels
Arrange conversion factor so starting unit is on the bottom of the conversion factor
• May string conversion factors
So we do not need to know every relationship, as long as we can find something else the beginning and ending units are related to unit 1 x unit 2 unit 1
= unit 2
1.
Dimensional Analysis Exercise 1: Convert 7.8 km to miles
Write down the Given quantity and its unit
2.
Write down the quantity you want to Find and unit
3.
Write down the appropriate
Conversion Factors
4.
Write a Solution Map
5.
Follow the Solution Map to
Solve the problem
6.
Sig. Figs. and Round
Given:
Find:
Conversion
Factors:
Solution
Map:
Solution:
Round: km
0 .
6214 mi
1 km mi
7.8
km
0 .
6214 mi
1 km
4.84692
mi
4.
1 km = 0.6214 mi
8
7.8 km
? miles
4692 mi = 4.8 mi
7.
Check Check: Units & Magnitude are correct
1.
Dimensional Analysis Exercise 2: Convert 20.0 lbs to kg
Write down the Given quantity and its unit
2.
Write down the quantity you want to Find and unit
3.
Write down the appropriate
Conversion Factors
4.
Write a Solution Map
5.
Follow the Solution Map to
Solve the problem
6.
Sig. Figs. and Round
Given:
Find:
Conversion
Factors:
Solution
Map:
Solution:
Round:
1 kg = 2.205 pounds lbs kg
2 .
205 lb
1 kg
20 lbs
1 kg
2.205
lbs
9.07029
kg
9.
0
20.0 lbs
? kg
7029 kg = 9.1 kg
7.
Check Check: Units & Magnitude are correct
1.
Dimensional Analysis Exercise 3: How many cups of cream is 0.75 L?
Write down the Given quantity and its unit
2.
Write down the quantity you want to Find and unit
3.
Write down the appropriate
Conversion Factors
4.
Write a Solution Map
Given:
Find:
Conversio n Factors:
Solution
Map:
0.75 L
? cu
1 L = 1.057 qt
1 qt = 4 cu
5.
6.
Follow the Solution Map to
Solve the problem
Sig. Figs. and Round
Solution:
Round:
L
1 .057
qt
1 L qt cu
4 cu
1 qt
0 .
75 L
1 .057
qt
1 L
4 cu
1 qt
3 .
171 cu
3.
1 71 cu = 3.2 cu
7.
Check Check: Units & Magnitude are correct
Converting Quantities Involving Units Raised to a Power
Convert Cubic Inches into Cubic Centimeters
1) Find Relationship Equivalence: 1 in = 2.54 cm
2) Write Solution Map in 3 cm 3
3) Change Equivalence into Conversion Factors with Starting
Units on the Bottom
2.54
cm
1 in
3
2.54
3 cm
3
1
3 in
3
16.4
cm
3
1 in
3
1.
2.
Write down the quantity you want to Find and unit
3.
Write down the appropriate
Conversion Factors
4.
Write a Solution Map
5.
6.
Convert 2,659 cm 2 into square meters
Write down the Given quantity and its unit
Follow the Solution Map to
Solve the problem
Sig. Figs. and Round
Given:
Find:
Conversion
Factors:
Solution
Map:
Solution:
Round:
2,659 cm
? m 2
2
1 cm = 0.01 m cm 2
0 .01
m
1 cm
2 m 2
2,659 cm
2
1
10
4 m
1 cm
2
2
0 .
2659 m
2
0.2659 m 2
7.
Check Check: Units & Magnitude are correct
Volume vs Mass of Brass y = 8.38x
160
140
120
100
80
60
40
20
0
0.0
2.0
4.0
6.0
8.0
10.0
Volume, cm3
12.0
14.0
16.0
18.0
Density
Ratio of mass:volume
Solids = g/cm 3
1 cm 3 = 1 mL
Liquids = g/mL
Gases = g/L
Density
Mass
Volume
Volume of a solid can be determined by water displacement – Archimedes
Principle
Density : solids > liquids >>> gases except ice is less dense than liquid water!
Density
• For equal volumes, denser object has larger mass
• For equal masses, denser object has smaller volume
• Heating objects causes objects to expand
does not effect their mass!!
How would heating an object effect its density?
• In a heterogeneous mixture, the denser object sinks
Why do hot air balloons rise?
Density
Volume
Mass
Volume
Density
Mass
Density m, V
Solution Maps:
D m, D V
Mass
Density
Volume
V, D m
Density as a Conversion Factor
• The gasoline in an automobile gas tank has a mass of 60.0 kg and a density of 0.752 g/cm 3 . What is the volume?
• Given: 60.0 kg
• Find: Volume in L
• Conversion Factors:
0.752 grams/cm 3
1000 grams = 1 kg
Density as a Conversion Factor
Exercise:
• A 55.9 kg person displaces 57.2 L of water when submerged in a water tank. What is the density of the person in g/cm 3 ?
