CHM 1210 1st Edition Lecture 3Outline of Last lectureI. Matter and Energy (con)c. Classes of Matterd. Properties of MatterOutline of Current LectureII. Matter and Energy (con)a. Atomic Theoryb. Molecular Viewc. Coastd. Making Measurements e. Unit conversionsf. Temperture scalesCurrent Lecture1.5 Atomic Theory: The Scientific Method in Action Definitions: oScientific method = an approach to acquiring knowledge based on observation of phenomena, development of a testable hypothesis, and additional experiments that test the validity of the hypothesis oScientific law = a concise and generally applicable statement of a fundamental scientific principle oScientific theory = a general explanation of widely observed phenomena that has been extensively tested oHypothesis = a tentative and testable explanation for an observation or a series of observations oLaw of Definite Proportions - Different samples of a pure chemical substance always contain The same proportion of elements by mass_ It is equivalent to the Law of Constant Composition. Joseph Proust (1754-1826) Example: By mass, water (H2O) is: 1 part H = 11.2% and 8 part O= 88.8%H2O: 2g/mol + 16g/mol = 18g/mol : 1004 These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• Law of Multiple Proportions – Elements can combine in different ways to form different substances, whose mass ratios are ___small whole# multiples of each other__. Example: nitric monoxide (NO) nitrogen dioxide (NO2) Five ways to represent the arrangement of atoms in molecules 1.7 COAST: A framework for solving problems • Collect and Organize oIdentify key concepts and key terms used to express the concept(s), sort through the information given in the problem, and assemble any supplemental information that may be needed (equations, definitions, and constants). oAnalyze oEvaluate information and relationships or connections; sometimes units will help identify steps needed to solve the problem. oSolve oPerform calculations, check units, etc. oThink about it oIs the answer reasonable? Are the units correct? 1.8 Making measurements and expressing the results Obs: oMeasurements oEssential for characterizing __the physical and chemical properties of matter__ • Two parts of every measurement: 1.875 lbs Number Unit oStandardization of the units of measurement is essential 1.8 Making MeasurementsObs: All other units of measure are _derived_ from these seven fundamental SI units.Table will not be on test (Memorize this)!!!Practice problems: 1) 1 km = ? Mm Kilo to base= 10^3 + base to meter= 10^3 kilo to meter = 10^6 o1ng= ? GgNano to base= 10^-9 + base to giga= 10^-9 Nano to Giga = 10^-18 *****practice for test***Obs: oAll measurements contain _uncertainty_______. oA digit that must be estimated is called _uncertain (last digit recorded)______. oOne must include all digits known with _certainty__ plus one digit that is __uncertain__. 0 1 2 3 4 1.7 cm < length < 1.8 cm length = _1.75 plus or minus 0.05Definitions: Accuracy = how close a measurement is to the true valuePrecision = how close a 3 of independent measurements agree with each otherPractice Problem: The mass of a tennis ball was measured in triplicates using a bathroom scale, a labbalance and an analytical balance. Describe the accuracy and precision of each measuring device taking into account that the true mass value is 54.44178 g. Poor accuracy fairly accurate accurate Poor precision poor precision precise Definitions: Significant figures (SF) = the total number of _meaningful_ digits in a measured or calculated quantity. Exact number = a number whose value is known with ___complete certainity__. Obs: Exact numbers and relationships such as __7 days a week, 5 fingers on a hand, have a infinite # of Significant Figures_. Rules for counting significant figures (left-to-right) oAll non-zero digits are significant. 1.6 SF= 2oInterior zeros are significant. 1.06 SF=33. Leading zeros are not significant. 0.00106 SF=3 scientific notation 1.06x 10^-3 4. Trailing zeros may or may not be significant a. Trailing zeros after a decimal point are significant. 1.060 SF=4 b. Zeros at the end of a number without a written decimal point are ambiguous and should be avoided by using scientific notation. 160 SF=2 1.6x 10^2Not correct way to write SF=3 1.6x 10^3 Rules for determining significant figures in mathematical operations “Weakest link” Principle: The number of significant figures in the final result cannot be greater than the _weakest link_ used in the calculation.1) Multiplication or division: The final answer cannot have more significant figures than any of the original numbers. Ex. 278.0mi = 2.780x 10^2 mi = 2.375053395 = 2.375x 10^1 mi/gal 11.705 gal 1.1705x 10^1 gal 2) Addition or subtraction: The final answer cannot have more digits to the right of the decimal point than any of the original numbers. 3.18mi+2.01315mi5.19315mi = 5.19miRules for rounding off numbers 1. If the first digit you remove is less than 5, round down by dropping it and all following numbers. 5.664525=5.6652. If the first digit you remove is 6 or greater, round up by adding 1 to the digit on the left. 5.664525 = 5.663. If the first digit you remove is 5 and there are more nonzero digits following, round up. 5.664525=5.6654. If the digit you remove is a 5 with nothing following, round down. 5.664525=5.66452 1.9 Units Conversions and Dimensional Analysis Definitions: oConversion Factor = A fraction in which the numerator and denominator represent __equivalent qualities__, but expressed in _different units___________. o1 km = 0.6214 mi  1km/0.6214mi or 0.6214mi/1km oDimensional Analysis = converting a value from one unit to another: Practice problem: The summit of Mount Washington in New Hampshire is famous for its awful weather: it experiences hurricane-force winds an average of 110 days per year. On April 12, 1934, a wind gust of 231 miles per hour was recorded at the summit. What is this wind speed in meters per second?1.10 Temperature Scales Celsius to Kelvin Kelvin to