1
Chapter 1 Chemical Foundations
1.3 Units of Measurement
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
2
Measurement
You make a measurement every time you
• measure your height. • read your watch.• take your temperature.• weigh a cantaloupe.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
3
Measurement in Chemistry
In chemistry we
• measure quantities.• do experiments.• calculate results. • use numbers to report
measurements.• compare results to
standards.Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
4
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.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
5
Stating a Measurement
In every measurement, a number is followed by a unit.
Observe the following examples of measurements:
Number and Unit35 m
0.25 L225 lb3.4 hr
6
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.
7
The 7 Basic Fundamental SI Units
Physical Quantity Name of Unit AbbreviationMass kilogram kg
Length meter m
Time second s
Temperature kelvin K
Electric current ampere A
Amount of substance mole mol
Luminous intensity candela cd
8
Units in the Metric System
In the metric and SI systems, one unit is used for each type of measurement:
Measurement Metric SILength meter (m) meter (m)Volume liter (L) cubic meter (m3)Mass gram (g) kilogram (kg)Time second (s) second (s)Temperature Celsius (°C) Kelvin (K)
9
Length Measurement
Length • is measured using a
meter stick.
• uses the unit of meter (m) in both the metric and SI systems.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
10
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
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
11
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.Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
12
Mass Measurement
The mass of an object
• is the quantity of material it 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
13
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.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
14
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.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
15
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 in1) 19.6 s. 2) 14.2 min. 3) 3.5 hr.
C. The mass of a lemon is1) 12 oz. 2) 0.145 kg. 3) 0.6 lb.
D. The temperature is1) 85°C. 2) 255 K. 3) 45°F.
16
Solution
A. John’s height is3) 2.1 m.
B. The race was won in1) 19.6 s.
C. The mass of a lemon is2) 0.145 kg.
D. The temperature is2) 255 K.
17
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. Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
19
Comparing Numbers in Standard and Scientific Notation
Here are some numbers written in standard formatand in scientific notation.
Number in Number in Standard Format Scientific Notation
Diameter of the Earth12 800 000 m 1.28 x 107 m
Mass of a human68 kg 6.8 x 101 kg
Length of a pox virus0.000 03 cm 3 x 10-5 cm
20
Learning Check
Select the correct scientific notation for each.
A. 0.000 0081) 8 x 106 2) 8 x 10-6 3) 0.8 x 10-5
B. 72 0001) 7.2 x 104 2) 72 x 103 3) 7.2 x 10-4
21
Solution
Select the correct scientific notation for each.
A. 0.000 0082) 8 x 10-6
B. 72 0001) 7.2 x 104
22
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
25
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
Learning Check
26
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
Solution
27
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
Learning Check
28
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
Solution
29
A megamile is how many times farther than 103 kilomiles?1) 102) 10003) they are the same4) 1005) 0.1
Learning Check
30
A megamile is how many times farther than 103 kilomiles?
3) they are the same
Solution
1000 = 103 and kilomiles=1000, so 1000*1000=106 = megamile
31
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 cm1 m = 1000 mm
Metric Equalities
34
Measuring Mass
Several equalities can bewritten for mass in themetric (SI) system
1 kg = 1000 g1 g = 1000 mg1 mg = 0.001 g1 mg = 1000 µg
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
35
Indicate the unit that completes each of the followingequalities.
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 = 1) 1 ms 2) 1 cs 2) 1 ds
D. 0.01 m = 1) 1 mm 2) 1 cm 2) 1 dm
Learning Check
37
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
Learning Check