Chapter 1, Section

Chapter 1 Chemical Foundations

1.3 Units of Measurement

1 Measurement

You make a measurement every time you

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

2 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

3 Measurement

In a measurement

• a measuring tool is used to compare some dimension of an object to a standard.

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

5 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.

6 The 7 Basic Fundamental SI Units

Physical Quantity Name of Unit Abbreviation Mass kilogram kg Length meter m Time second s Temperature kelvin K Electric current ampere A Amount of substance mole mol Luminous intensity candela cd

7 Units in the Metric System

In the metric and SI systems, one unit is used for each type of measurement: Measurement Metric SI Length 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)

8 Length Measurement

Length • is measured using a meter stick. • uses the unit of meter (m) in both the metric and SI systems.

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

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.

11 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.

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.

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.

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.

15 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.

16 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.

17 Some Powers of Ten

18 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

19 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

20 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

21 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

22 Solution

Write each as a standard number.

A. 2.0 x 10-2 3) 0.020

B. 1.8 x 105 1) 180 000

23 Metric and SI Prefixes

24 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

25 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

26 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

27 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

28 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

29 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

30 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

31 Measuring Length

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

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 = 1) 1 ms 2) 1 cs 2) 1 ds

D. 0.01 m = 1) 1 mm 2) 1 cm 2) 1 dm

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

37 Solution

Complete each of the following equalities.

A. 1 kg = 1000 g (3)

B. 1 mm = 0.001 m (1)