Chapter 1 Chemical Foundations - Department of...

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Chapter 1 Chemical Foundations

1.3 Units of Measurement

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Measurement

You make a measurement every time you

• measure your height. • read your watch.• take your temperature.• weigh a cantaloupe.


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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

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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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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

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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 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

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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 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)

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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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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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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

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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

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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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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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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.

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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.

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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. Copyright © 2005 by Pearson Education, Inc.

Publishing as Benjamin Cummings

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Some Powers of Ten

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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

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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

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Solution

Select the correct scientific notation for each.

A. 0.000 0082) 8 x 10-6

B. 72 0001) 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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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

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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

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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

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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

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A megamile is how many times farther than 103 kilomiles?1) 102) 10003) they are the same4) 1005) 0.1

Learning Check

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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

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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

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Measuring Length


33Measuring Volum

e

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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


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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

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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

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Complete each of the following equalities.

A. 1 kg = 1000 g (3)

B. 1 mm = 0.001 m (1)

Solution

Chapter 1 Chemical Foundations - Department of...

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