Chapter 1
Chemical Foundations
1.3
Units of Measurement
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Measurement
You make a measurement
every time you
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measure your height.
read your watch.
take your temperature.
weigh a cantaloupe.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Measurement in Chemistry
In chemistry we
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measure quantities.
do experiments.
calculate results.
use numbers to report
measurements.
compare results to
standards.
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3
Measurement
In a measurement
• a measuring tool is used
to compare some
dimension of an object
to a standard.
• of the thickness of the
skin fold at the waist,
calipers are used.
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4
Stating a Measurement
In every measurement, a number is followed by a unit.
Observe the following examples of measurements:
Number and Unit
35
m
0.25
L
225
lb
3.4
hr
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The Metric System (SI)
The metric system or SI (international system) is
• a decimal system based on 10.
• used in most of the world.
• used everywhere by scientists.
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The 7 Basic Fundamental SI Units
Physical Quantity
Mass
Length
Time
Temperature
Electric current
Amount of substance
Luminous intensity
Name of Unit
Abbreviation
kilogram
kg
meter
m
second
s
kelvin
K
ampere
A
mole
mol
candela
cd
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Units in the Metric System
In the metric and SI systems, one unit is used for each
type of measurement:
Measurement
Length
Volume
Mass
Time
Temperature
Metric
meter (m)
liter (L)
gram (g)
second (s)
Celsius (°C)
SI
meter (m)
cubic meter (m3)
kilogram (kg)
second (s)
Kelvin (K)
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Length Measurement
Length
• is measured using a
meter stick.
• uses the unit of meter
(m) in both the metric
and SI systems.
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9
Inches and Centimeters
The unit of an inch is
equal to exactly 2.54
centimeters in the metric
(SI) system.
1 in. = 2.54 cm
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10
Volume Measurement
Volume
• is the space occupied by a
substance.
• uses the unit liter (L) in
metric system.
•
1 L = 1.057 qt
• uses the unit m3(cubic
meter) in the SI system.
• is measured using a
graduated cylinder.
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Publishing as Benjamin Cummings
11
Mass Measurement
The mass of an object
• is the quantity of material it
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contains.
is measured on a balance.
uses the unit gram (g) in the
metric system.
uses the unit kilogram (kg)
in the SI system.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
12
Temperature Measurement
The temperature of a substance
• indicates how hot or cold it is.
• is measured on the Celsius
(°C) scale in the metric
system.
• on this thermometer is 18ºC
or 64ºF.
• in the SI system uses the
Kelvin (K) scale.
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13
Time Measurement
Time measurement
• uses the unit second(s)
in both the metric and SI
systems.
• is based on an atomic
clock that uses a
frequency emitted by
cesium atoms.
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Publishing as Benjamin Cummings
14
Learning Check
Identify the measurement that has an SI unit.
A. John’s height is
1) 1.5 yd.
2) 6 ft .
3) 2.1 m.
B. The race was won in
1) 19.6 s.
2) 14.2 min.
3) 3.5 hr.
C. The mass of a lemon is
1) 12 oz.
2) 0.145 kg.
3) 0.6 lb.
D. The temperature is
1) 85°C.
2) 255 K.
3) 45°F.
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Solution
A. John’s height is
3) 2.1 m.
B. The race was won in
1) 19.6 s.
C. The mass of a lemon is
2) 0.145 kg.
D. The temperature is
2) 255 K.
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Scientific Notation
Scientific notation
• is used to write very large
or very small numbers.
• for the width of a human
hair of 0.000 008 m is
written 8 x 10-6 m.
• of a large number such
as 4 500 000 s is written
4.5 x 106 s.
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17
Some Powers of Ten
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Comparing Numbers in Standard
and Scientific Notation
Here are some numbers written in standard format
and in scientific notation.
Number in
Number in
Standard Format
Scientific Notation
Diameter of the Earth
12 800 000 m
1.28 x 107 m
Mass of a human
68 kg
6.8 x 101 kg
Length of a pox virus
0.000 03 cm
3 x 10-5 cm
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Learning Check
Select the correct scientific notation for each.
A. 0.000 008
1) 8 x 106
2) 8 x 10-6
3) 0.8 x 10-5
B. 72 000
1) 7.2 x 104
2) 72 x 103
3) 7.2 x 10-4
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Solution
Select the correct scientific notation for each.
A. 0.000 008
2) 8 x 10-6
B. 72 000
1) 7.2 x 104
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Learning Check
Write each as a standard number.
A. 2.0 x 10-2
1) 200
2) 0.0020
3) 0.020
B. 1.8 x 105
1) 180 000
2) 0.000 018
3) 18 000
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Solution
Write each as a standard number.
A. 2.0 x 10-2
3) 0.020
B. 1.8 x 105
1) 180 000
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Metric and SI Prefixes
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Learning Check
Indicate the unit that matches the description.
1. A mass that is 1000 times greater than 1 gram.
1) kilogram
2) milligram
3) megagram
2. A length that is 1/100 of 1 meter.
1) decimeter
2) centimeter
3) millimeter
3. A unit of time that is 1/1000 of a second.
1) nanosecond 2) microsecond
3) millisecond
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Solution
Indicate the unit that matches the description.
1. A mass that is 1000 times greater than 1 gram.
1) kilogram
2. A length that is 1/100 of 1 meter.
2) centimeter
3. A unit of time that is 1/1000 of a second.
3) millisecond
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Learning Check
Select the SI unit you would use to measure
A. your height.
1) millimeters 2) meters
3) kilometers
B. your mass.
1) milligrams
2) grams
3) kilograms
C. the distance between two cities.
1) millimeters 2) meters
3) kilometers
D. the width of an artery.
1) millimeters 2) meters
3) kilometers
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Solution
A. your height.
2) meters
B. your mass.
3) kilograms
C. the distance between two cities.
3) kilometers
D. the width of an artery.
1) millimeters
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Learning Check
A megamile is how many times farther
than 103 kilomiles?
1) 10
2) 1000
3) they are the same
4) 100
5) 0.1
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Solution
A megamile is how many times farther
than 103 kilomiles?
3) they are the same
1000 = 103 and kilomiles=1000, so
1000*1000=106 = megamile
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Metric Equalities
An equality
states the same measurement in two different units.
can be written using the relationships between two
metric units.
Example: 1 meter is the same as 100 cm and 1000
mm.
1 m = 100 cm
1 m = 1000 mm
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Measuring Length
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32
Measuring Mass
Several equalities can be
written for mass in the
metric (SI) system
1 kg = 1000 g
1 g = 1000 mg
1 mg = 0.001 g
1 mg = 1000 µg
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
34
Learning Check
Indicate the unit that completes each of the following
equalities.
A.
1000 m = 1) 1 mm
2) 1 km
2) 1 dm
B.
0.001 g = 1) 1 mg
2) 1 kg
2) 1 dg
C.
0.1 s
2) 1 cs
2) 1 ds
D.
0.01 m = 1) 1 mm
2) 1 cm
2) 1 dm
= 1) 1 ms
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Learning Check
Complete each of the following equalities.
A. 1 kg =
1) 10 g
2) 100 g
3) 1000 g
B. 1 mm =
1) 0.001 m
2) 0.01 m
3) 0.1 m
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Solution
Complete each of the following equalities.
A. 1 kg
= 1000 g
B. 1 mm = 0.001 m
(3)
(1)
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