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##### Chem 140 Section A Instructor: Ken Marr

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**Chem 140 Section AInstructor: Ken Marr**Weekly Schedule “Lecture” 9 -10, MWF in STB-2 “Lab” 8 -10 , Tu in STB-2 8 -10 , Th in STB-5**Chem 140 Section CInstructor: Ken Marr**Weekly Schedule “Lecture” 10 –11, MWF in STB-2 “Lab” 10-12 , Tu in STB-2 10-12 , Th in STB-5**Chem 140 Section EInstructor: Ken Marr**Weekly Schedule “Lecture” 1 - 2, MWF in STB-2 “Lab” 1 - 3 , Tu in STB-2 1 - 3 , Th in STB-5**Day 1 Activities**• Introduction to Course • Briefly Review Course Outline/Syllabus • Homework Assignments • Reading: See Chem 140 schedule • Lab: Do Prelab assignment for the “Measurement and Density” Lab • Stamped Assignment #1: Chapter 1 HW • due Tues. 10/01/02 ……But start now!!! • Note: 10/2 is a very special day for your instructor!! • Begin Chapter 1 • Alice 1 and 2**CHEMISTRY**The Study of Matter and the Changes that Matter Undergoes and The Energy Associated with The Changes**Chemistry as the Central Science**Engineering Physics Atmospheric Sciences Oceanography Medicine Economics Governments Chemistry People Geology Biology Politics Astronomy Anthropology**Chapter# 1 : Keys to the Study of Chemistry**1.1 Some Fundamental Definitions 1.2 Chemical Arts and the Origins of Modern Chemistry 1.3 The Scientific Approach: Developing a Model 1.4 Chemical Problem Solving 1.5 Measurement in Scientific Study 1.6 Uncertainty in Measurement: Significant Figures**Measurement and Significant Figures**• Measured Numbers are Never Exact...Why? • Which Graduated Cylinder is the most precise? • How is precision indicated when we record a measurement?**The Number of Significant Figures in a**Measurement Depends Upon the Measuring Device Fig 1.14 3e**Significant Figures**• We use significant figures to indicate the maximum precision of a measurement • Significant Figures • The number of digits that are known with certainty, plus one that is uncertain • Significant figures are used only with measured quantities. • Some numbers are exact and do not have any uncertainty......e.g...’s??**More Examples**• Record the exact length in centimeters, cm (T2c) • Record the exact amounts for numbers 1-11 (T2d)**Sig. Fig. Rules to memorize.....(See page 27-30 Silberberg**3e) • All nonzero numbers are significant e.g. 23.8 g, 2345 km, 11 mL, 5 inches • Zeros between nonzero digits are significant i.e. Sandwiched zeros are significant e.g. 509 m, 2001 mL, 2050.1 L • Zeros preceding the 1st nonzero digit are not significant.......they serve only to locate the decimal point e.g. 0.083 m, 0.000306 L • Try converting these numbers to Scientific Notation to prove this!**More Sig. Fig. Rules Involving Zeros**• Zeros at the end of number that include a decimal point are significant • 0.800, 11.40, 10.00, 400. • Zeros at the end of a number without a decimal point are not significant... The Greenwater Rule! • 40, 8800, 300, • Use of underlining and decimal points**Examples of Significant Digits in Numbers**Number - Sig digits Number - Sig digits 0.0050 L 1.34000 x 107 nm 0.00012 kg 87,000 L 83.0001 L 78,002.3 ng 0.006002 g 0.000007800 g 875,000 oz 1.089 x 10 -6L 30,000 kg 0.0000010048 oz 5.0000 m3 6.67000 kg 23,001.00 lbs 2.70879000 ml 0.000108 g 1.0008000 kg 1,470,000 L 1,000,000,000 g**Rounding off Numbers**• Rounding off is used to drop non-significant numbers • Rule 1 When the 1st digit after those you want to retain is 4 of less, that digit and all others to the right are dropped • Round off the following to 3 sig. figs. • 105.29, 189.49999, 1.003, 100.3, 1001**Rounding off Numbers**• Rule 2 When the 1st digit after those you want to retain is 5 or greater, that digit and all others to the right are dropped and the last digit retained is increased by one • Round off the following to 4 sig. figs. • 10.87519, 13.59800, 99.999, 1042.5**Sig. Figs. in Calculations**• The Central Idea..... • The result of a calculation based on measurements can not be more precise than the least precise measurement! • Some Rules to, yes, memorize......**Sig. Figs. in Multiplication and Division**• “The Chain Rule” • Your answer must contain the same number of sig figs as the measurement with the fewest sig figs.....Some e.g...’s... (3.04) x (2.2) = 6.688 = ??? (2.00) / (0.3 ) = 6.666... = ??? (18.4) x (4.0) = 1.1117824 = ??? (66.2)**Sig. Figs. in Addition and Subtraction**• “The Decimal Rule” • The answer must have the same precision as the least precise measurement...or... • Your answer must be expressed to the same number of decimal places as the measurement with the fewest decimal places. • The number of sig figs are not considered, only the number of decimal places are considered!!! • Some examples..**Sig. Figs. in Addition and Subtraction**• Examples..... • 12.89 + 12.1 + 11.803 + 19 = 55.793 = ? • 1786 - 130 = 1656 = ??? • 7331 + 0.495 = 7331.495 = ???**Scientific Notation**• Scientific Notation • Writing a number as a number between 1 and 10 times a power of 10 • WHY DO IT??? • The Rules...**How to Write Numbers in Scientific Notation**• Move the decimal point in the original number so that it is located after the first nonzero digit • e.g. 5682 ???? • Multiply this number by the proper power of 10 • The power of 10 is equal to the number of places the decimal point was moved. • POSITIVE IF MOVED TO THE LEFT • NEGATIVE IF MOVED TO THE RIGHT**Examples....**• Express the following numbers in scientific notation... • 0.0421 • 150,000 • 5899 • Express the following in “longhand” • 5.30 x 10-4 • 8.000 x 106**Meaning of Powers of 10**• 103 = 10-3 = • 102 = 10-2 = • 101 = 10-1 = • 100 =**Metric System**• System of measure built around standard or base units • Uses factors of 10 to express larger or smaller numbers of these units**Table 1. 2 (p. 17, 3e) SI - Base Units**Physical Quantity Unit Name 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**Metric Base Units and their Abbreviations**• Length • Mass • Volume • Temperature • Prefixes are added to these base units for quantities larger or smaller than the base unit • Prefixes are a multiple of 10**Table 1.3Common Decimal Prefixes Used with SI Units.**Prefix Prefix Number Word Exponential Symbol Notation tera T 1,000,000,000,000 trillion 1012 giga G 1,000,000,000 billion 109 Mega M 1,000,000 million 106 Kilo k 1,000 thousand 103 hecto h 100 hundred 102 deka da 10 ten 101 ----- ---- 1 one 100 deci d 0.1 tenth 10-1 centi c 0.01 hundredth 10-2 milli m 0.001 thousandth 10-3 micro millionth 10-6 nano n 0.000000001 billionth 10-9 pico p 0.000000000001 trillionth 10-12 femto f 0.000000000000001 quadrillionth 10-15**Common Metric Prefixes**• Memorize the Symbol, Numerical Value, and Power of 10 Equivalent for..... • kilo- • centi- • milli- • micro- • nano-**Common Prefix Applications**• Length: • km 1 km = ? m • cm 1 cm = ? m • mm 1 mm = ? m • µm 1 µm = ? m • nm 1 nm = ? m**Common Prefix Applications**• Mass • kg 1 kg = ? g • mg 1 mg = ? g • µg 1 µg = ? g**Common Prefix Applications**• Volume • mL 1 mL = ? L • µL 1 µL = ? L**Important Relationships**• Length • 1 m = ?? cm • 1 m = ?? mm • 1 m = ?? µm • 1 cm = ?? mm**Important Relationships**• Mass • 1 g = ?? mg • 1 kg = ?? g • 1 kg = ?? lb..**Important Relationships**• Volume • 1 L = ?? mL • 1 mL = ?? cm3 • 1 L = ?? cm3 • 1 L = 1.057 qt.**Solving Chemistry ProblemsDevelop a Plan Carryout Plan** Check Answer • Developing a Plan: Read the problem carefully! • Clarify the know and unknown: • What information is given? • What are you trying to find? • Think about how to solve the problem before you start to juggle numbers • Suggest steps from the known to unknown • Determine principles involved and the relationships needed • Use sample problems as a guides • Map out the strategy you will follow**Solving Chemistry Problems (cont.)**• Solve the problem: Carry out your plan • Set up problem in a neat, organized, and logical way! • Unwanted units should cancel to give the desired unit of measure • Make a rough estimate of the answer before using your calculator • Round off to correct number of sig. figs. • Answer must have correct units**Solving Chemistry Problems (cont.)**• Check your answer • Is it reasonable? • Correct nits? • Same “ballpark” as a rough estimate? • Makes chemical sense?**Problem Solving: Some Examples**• How many hours would it take a pump to remove the water from a flooded basement that is about 30 feet wide and 50 feet long with water at a depth of about 2 feet? The pump has a capacity of 80 liters per minute. See Table 1.4, Common SI-English Equivalent Quantities, page 18 Silberberg 3e. 1062 min = 17.7 hours = 20 hours**Metric Conversion Factors**• Be able to do conversions within the metric system involving the common metric prefixes • kilo- • centi- • milli- • micro- • nano- • e.g. #32 on page 43**Metric - English Conversions**• Given metric - English conversion factors, be able to convert between these two systems • You do not have to memorize metric to English conversions factors**Measurement of Temperature**• Heat vs. Temperature • Temperature (SI unit: Kelvin, K) • A measure of how hot or cold an object is relative to another object • Also measured in degrees Celsius, oC • Heat (SI unit: joule, J) • The energy transferred between objects at different temperatures • A form of energy associated with the motion of atoms and molecules (the small particles of matter) • Also measured in calories, cal**Application: Heat vs. Temperature**• Which contains more heat... • 1 mL of water at 90 oC or 1 liter of water at 90 oC ? • 1 burning match or 10 burning matches?**Temperature Conversions**The boiling point of Liquid Nitrogen is - 195.8 oC, what is the temperature in Kelvin and degrees Fahrenheit? T (in K) = T (in oC) + 273.15 T (in K) = -195.8 + 273.15 = 77.35 K = 77.4 K T (in oF) = 9/5 T (in oC) + 32 T (in oF) = 9/5 ( -195.8oC) +32 = -320.4 oF The normal body temperature is 98.6oF, what is it in Kelvin and degrees Celsius? T (in oC) = [ T (in oF) - 32] 5/9 T (in oC) = [ 98.6oF - 32] 5/9 = 37.0 oC T (in K) = T (in oC) + 273.15 T (in K) = 37.0 oC + 273.15 = 310.2**Density**• Density = mass (g) / Volume(mL or cm3 or L) • Physical characteristic of a substance • Aids in identification of a substance • Calculated by..... • divide the mass of a substance by the volume occupied by that mass • Units • mass in grams • volume • Solids and Liquids: mL or cm3 • Gasses: L**Density**• Densities vary with temperature! • Why?? • Would you expect densities to increase or decrease as the temperature increases?**Density**• Immiscible liquids and solids separate into layers according to their densities • List the order from top to bottom when the following are mixed • Hg (13.5525 g/mL) • Carbon Tetrachloride (1.59525 g/mL) • Mg (1.7425 g/mL) • Water (1.004 g/mL) • What do the superscripts mean next to each density listed above?**Calculations Involving Density**• Be able to calculate the density, mass, or volume of a substance • Use the plug and chug method or use density as a conversion factor • Practice makes perfect....**Specific Gravity**• Compares the density of a liquid or solid to that of water... Units??? • Sp. Gravity = dsolid or liquid / dwater • Usually use dwater @ 4oC = 1.000g/mL • Compares the density of a gas to that of air...... Units??? • Sp. Gravity = dgas/ dair