CHEM 101 1nd Edition Lecture 3 Outline of Last Lecture I. Classifying Matter - CompoundsII. Physical Properties of MatterIII. Chemical PropertiesIV. Units of MeasurementV. Units of EnergyVI. Precision and AccuracyOutline of Current Lecture I. The 2 Kinds of NumbersII. Rules of Significant FiguresIII. Dimensional AnalysisCurrent LectureIV. The 2 Kinds of Numbersa. Exact:i. There are 12 eggs in a dozenii. You have exactly 10 fingersiii. No more. No less.b. Inexacti. Any measurementV. Rules for significant figuresa. Leading zeros are never significanti. 0.12 has 2 significant figuresb. Imbedded zeros are always significanti. 1.02 has 3 significant figuresc. Trailing zeros are only significant if the decimal point is specifiedi. 120 has 2 significant figures, 120. has 3 sig figsd. Examples, with scientific notationi. 0.00682 3 sf 6.83 x 10-3ii. 300 1 sf 3 x 102iii. 300.0 4 sf 3.000 x 102e. When adding or subtracting, the last digit retained is set by the digit with fewest digits after decimal (doubtful digit)i. 10.5 300 300.0These 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.ii. 10.52 256 256iii. 10.591 130 130. iv. 31.611 = 31.6 686 = 700 686.0 = 686f. Multiplication or division: answer contains no more significant figures than the least accurately known numberi. 2.8723 200 200.0 200.0ii. x 1.6 x6.0 x 6.0 x6.00iii. 4.59586 = 4.6 1200.0 = 1000 1200.00 = 1200 1200.000 = 1.20 x 103g. You have 11 nickels that are worth 5 cents each. How much money in cents do you have (using correct significant figures)?i. 55 centsii. Money represents exact amount, a dollar is always 1 dollar.h. Each of the 11 nickels weighs 5 grams. What is the total weight?i. 60 gi. Really 55, but because of the different significant figures you roundVI. Dimensional Analysisa. This is a problem-solving method that uses the fact that any number or expression can be multiplied by 1 without changing its value.b. Unit factors may be made from any two terms that describe the same or equivalent "amounts" of what we are interested in. c. Do in one continuous calculationd. If 1, just 1, number in a calculation has fewer significant figures than every other number in the problem; the answer must have that few significant figures. e. Conversion factors are exact numbersf. Look and read instructions carefully for whether it asks for scientific notation or not.g. Examplei. How many centimeters are in 6.00 inches?1. (1 in / 2.54 cm) unit factor2. ? cm = 6.00 in x 2.54 cm/ 1 in = 15.2 cm (3 significant
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