Chapter 1 Chemical Foundations 1.3 Units of Measurement

Transcription

1 Chapter 1 Chemical Foundations 1.3 Units of Measurement Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 1

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 2

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 3

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 4

5 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

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. 6

7 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

8 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 (m 3 ) Mass gram (g) kilogram (kg) Time second (s) second (s) Temperature Celsius ( C) Kelvin (K) 8

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 9

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 10

11 Volume Measurement Volume is the space occupied by a substance. uses the unit liter (L) in metric system. 1 L = qt uses the unit m 3 (cubic meter) in the SI system. is measured using a graduated cylinder. Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 11

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 12

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 13

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 14

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 in 1) 19.6 s. 2) 14.2 min. 3) 3.5 hr. C. The mass of a lemon is 1) 12 oz. 2) kg. 3) 0.6 lb. D. The temperature is 1) 85 C. 2) 255 K. 3) 45 F. 15

16 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) kg. D. The temperature is 2) 255 K. 16

17 Scientific Notation Scientific notation is used to write very large or very small numbers. for the width of a human hair of m is written 8 x 10-6 m. of a large number such as s is written 4.5 x 10 6 Copyright 2005 by Pearson Education, Inc. s. Publishing as Benjamin Cummings 17

18 Some Powers of Ten 18

19 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 m 1.28 x 10 7 m Mass of a human 68 kg 6.8 x 10 1 kg Length of a pox virus cm 3 x 10-5 cm 19

20 Learning Check Select the correct scientific notation for each. A ) 8 x ) 8 x ) 0.8 x 10-5 B ) 7.2 x ) 72 x ) 7.2 x

21 Solution Select the correct scientific notation for each. A ) 8 x 10-6 B ) 7.2 x

22 Learning Check Write each as a standard number. A. 2.0 x ) 200 2) ) B. 1.8 x ) ) )

23 Solution Write each as a standard number. A. 2.0 x ) B. 1.8 x )

24 Metric and SI Prefixes 24

25 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

26 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

27 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

28 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

29 Learning Check A megamile is how many times farther than 10 3 kilomiles? 1) 10 2) ) they are the same 4) 100 5)

30 Solution A megamile is how many times farther than 10 3 kilomiles? 3) they are the same 1000 = 10 3 and kilomiles=1000, so 1000*1000=10 6 = megamile 30

31 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

32 Measuring Length Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 32

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34 Measuring Mass Several equalities can be written for mass in the metric (SI) system 1 kg = 1000 g 1 g = 1000 mg 1 mg = g 1 mg = 1000 µg Copyright 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 34

35 Learning Check Indicate the unit that completes each of the following equalities. A m = 1) 1 mm 2) 1 km 2) 1 dm B g = 1) 1 mg 2) 1 kg 2) 1 dg C. 0.1 s = 1) 1 ms 2) 1 cs 2) 1 ds D m = 1) 1 mm 2) 1 cm 2) 1 dm 35

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37 Learning Check Complete each of the following equalities. A. 1 kg = 1) 10 g 2) 100 g 3) 1000 g B. 1 mm = 1) m 2) 0.01 m 3) 0.1 m 37

38 Solution Complete each of the following equalities. A. 1 kg = 1000 g (3) B. 1 mm = m (1) 38