CHEM 105N 1st Edition Lecture 3 Outline of Last Lecture I. Definition of Scientific MethodA. Compare and contrast with Standard NumbersII. Measured vs. Known NumbersOutline of Current Lecture I. Significant Figures- Sandwiched Zeros- Trailing Zeros- Leading ZerosII. Exact NumbersIII. Multiplication and Division of Significant FiguresIV. Addition and Subtraction of Significant FiguresV. Metric EqualitiesCurrent LectureI. Significant Figures (Sig Figs):- Are obtained from a measurement in which all are the known and estimated digits are included- All non-zero numbers are SIGNIFICANT-Ex: 38.15 cm = 4 Sig Figs 1.88 kg = 3 Sig Figs - Sandwiched Zeros are SIGNIFICANT-Ex: 70.2 = 3 Sig Figs 12003 = 5 Sig Figs .0708 = 3 Sig Figs .390602 = 6 Sig Figs- Trailing Zeros (those that follow non-zero numbers without decimal points) are NOT SIGNIFICANT-Ex: 35000 = 2 Sig Figs 700 = 1 Sig Fig 6800500 = 5 Sig Figs 49000. = 5 Sig Figs- Leading Zeros are NEVER SIGNIFICANT-Ex: .004 = 1 Sig FigThese 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..0431 = 3 Sig Figs- In scientific notation, all numbers in the coefficient are significant-Ex: 3 x 10^4 = 1 Sig Fig 3.0 x 10^4 = 2 Sig Figs 3.00 x 10^4 = 3 Sig FigsII. Exact Numbers:- These are numbers you can count (ex: 4 socks) and defined equalities (ex: 1ft = 12 in)- In calculations, there must be the same number of sig figs as measured numbers- Must often ROUND- Exact numbers do not affect the number of sig figs- If a question requires a certain number of sig figs, significant zeros may be added-Ex: Three Sig Figs are allowed: 4 = 4.00 92 = 92.01.1 = 0.100- Extra values may also be rounded and removed:-Ex: Three Sig Figs are allowed:564.71 = 565.223456 = .223III. Multiplication and Division of Significant Figures:- When rounding, use the number with the lowest number of Sig Figs to determine the number of Sig Figs in your answer- Ex: 110.5 (4 Sfs) x .048 (2 Sfs) = 5.304 = 5.3 (rounded with 2 Sig Figs) IV. Addition and Subtraction of Significant Figures:- When rounding, use the number with the fewest decimal places to determine the number of decimal places in your answer-Ex. 25.2 (1 decimal place) + 1.34 (2 decimal places) = 26.54 = 26.5 (rounded with one decimal place)V. Metric Equalities:- An equality states the same measurement in two different units -Ex: 1 m = 100 cm = 10^2 cm 1 cm = 10 mm= 10^1 mm- Measurements of the same units use exact numbers- Measurements of different units (ex. Metric and US) use measured numbers and count as Significant Figures- Equalities are written as a fraction- Are represented with one equality in the numerator and one in the denominator-Ex. 60min/1hr OR 1hr/60min-Ex. The car was traveling at 92 mph = 1hr/92miles OR 92miles/1hr-Ex. One tablet contains 33 g of Potassium= 1 tablet/ 33g of Potassium OR 33g of Potassium/ 1