PRINCIPLES CHEMSTRY CHEM 120
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This 30 page Class Notes was uploaded by Carmela Kilback on Wednesday September 9, 2015. The Class Notes belongs to CHEM 120 at University of Washington taught by Staff in Fall. Since its upload, it has received 19 views. For similar materials see /class/192608/chem-120-university-of-washington in Chemistry at University of Washington.
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Date Created: 09/09/15
Chapter 1 Chemistry in Our Lives 11 Scientific Method Thinking like a Scientist canynml 2nn1 hy mmquot mummm Inc Pu l 1rl1 as Bm amn Currmngs Scientific Method The scienti c method is the process used by scientists to explain observations in nature Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Scientific Method The scienti c method involves Making Observations Writing a Hypothesis Doing Experiments Proposing a Theory Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Features of the Scientific Method Observations Facts obtained by observing and measuring events in nature Hypothesis A statement that explains the observations Experiments Procedures that test the hypothesis Theory A model that describes how the observations occur using experimental results Summary of the Scientific Method Scienti c Method Theory modified Hypnthesis if addititmal changed if experiments do W a 11 1 a H 3 experiments dun not support it 39 39 V W not support it Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Chapter 1 Measurements 12 Measurement and Scientific Notation Measurement You make a measurement every time you i I Measure your height 3 I Read your watch 39 Take your temperature Weigh a cantaloupe Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Measurement In a measurement I 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 Cnrlynuhl mm by Pezsnn gunman Inc Publishing as 3mmquot Currnlnus Stating 21 Measurement In every measurement a number is followed by a unit Observe the following examples of measurements Number and Unit 35 m 025 L 225 lb 34 hr 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 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 9 kilogram kg Time second s second s Temperature Celsius OC Kelvin K Length Measurement Length Is measured using a Metem gk meter stick a m m39r39sin uim39quotshuninn Uses the unit of meter m in both the metric and SI systems 1 meter 394 imlzm 1 ft 211 Mt Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Inches and Centimeters The unit of an inch I Jilillll lllllllllIlllihlllllll39l l llll lllll lllll centimeters In the Hummers metric SI system it 2 3 4 1 in 254 cm Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Volume Measurement Volume Is the space occupied by a substance Uses the unit liter L in metric system 1L106qt Uses the unit m3cubic meter in the SI system I Is measured using a graduated cylinder 1 L1u57 ql copyrlght 2007 by Pearson Eaucauon Inc Publishing as Eeruamln cummlngs Mass Measurement The mass of an object I Is a measure of the quantity of material it contains I Is measured on a balance I Uses the unit gram g in the metric system I Uses the unit kilogram kg in the SI system Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Temperature Measurement The temperature Indicates how hot or cold a substance is ls measured on the Celsius C scale in the metric system On this thermometer is 18 C or 64 F In the SI system uses the Kelvin K scale Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Time Measurement Time measurement Uses the unit second 3 in both the metric and SI systems Is based on an atomic clock that uses a frequency emitted by cesium atoms Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings Scienti c Notation Scientific notation I Is used to write very large or very small numbers For the width of a human hair 0000 008 m is written 8 x 106 m For a large number such as 4 500 000 s is written cwmmm hypmnmammm 45 X1068 quot 39 quot Writing Numbers in Scientific Notation A number in scientific notation contains a coefficient and a power of 10 coef cient power often coef cient power often 15 x 102 735 x 10394 To write a number in scientific notation the decimal point is placed after the first digit The spaces moved are shown as a power of ten 52 000 52 x 104 000378 378 x103 4 4 spaces left 3 spaces right Some Powers of Ten TABLE 1 392 Some Numbers Written as Powers of Ten Standard Number Multiples of Ten Scienti c Notation 10000 10x10x10gtlt10 1x104 1000 10x10x10 1x103 2 Some posmve 100 10 x 10 1 x 10 powers of ten 10 10 1 x 101 1 0 1 x 100 1 01 7 1 x 10391 10 1 1 1 2 7x x 0 01 10 10 100 l 10 Some negative 1 1 1 l 3 powers of ten 7x 7x x 0 001 10 10 10 1 000 1 10 1 1 1 1 1 4 7 7x 7x 7 7 x 0 000 1 10 10 10 10 10 000 1 10 Copyright 2007 by Pearson Education Inc Publishing as Benjamin Cummings 20 Comparing Numbers in Standard and Scientific Notation Here are some numbers written in standard format and in scientific notation Number in Standard Format Scientific Notation Diameter of the Earth 12800000m 128x107m Mass of a human 68 kg 68 x 101 kg Length of a virus 0000 03 cm 3 x105 cm 21 Learning Check Select the correct scientific notation for each A 0000 008 1 8x106 28x10396 308x10395 B 72000 1 72x104 272x103 372x104 22 Solution Select the correct scientific notation for each A 0000 008 2 8 x 10396 B 72 000 1 72x 104 23 Learning Check Write each as a standard number A 20x102 1 200 2 00020 B 18x 105 1 180 000 2 0000 018 3 0020 3 18 000 24 Solution Write each as a standard number A 20x 102 3 0020 B 18x105 1 180 000 25 Chapter 1 Measurements 13 Measured Numbers and Significant Figures l liiililllllllliIIlllllll lil llllil lllllll li39lllllll 1 2 3 4 5 cm Copyright 2007 by P eeee on Education Inc Publishing as Benjamin Cummings 26 Measured Numbers A measuring tool Is used to determine a quantity such as height or the mass of an object Provides numbers for a measuremen called measured numbers 247Mme 2am I dPam mmnn Inc Pmlimng s newquot anynun Reading 21 Meter Stick IZ34 cm The markings on the meter stick at the end of the blue line are read as The first digit 2 plus the second digit 27 The last digit is obtained by estimating The end of the line might be estimated between 27 28 as halfway 05 or a little more 06 which gives a reported length of 275 cm or 276 cm 28 Known Estimated Digits In the length reported as 276 cm The digits 2 and 7 are certain known The final digit 6 was estimated uncertain All three digits 276 are significant including the estimated digit 29
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