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Scientific Measurements. 3.1 Measurements and Their Uncertainty Essential Question. How do scientists accurately and precisely report measured quantities?. Scientific Notation. Form M x 10 n Rules for Addition & Subtraction Rules for Multiplication Rules for Division.
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3.1Measurements andTheir UncertaintyEssential Question • How do scientists accurately and precisely report measured quantities?
Scientific Notation • Form M x 10n • Rules for Addition & Subtraction • Rules for Multiplication • Rules for Division
Measurements and Uncertainty • Accuracy and Precision • Significant Figures • Direct Proportions • Indirect Proportions
Accuracy & Precision • Accuracy = closeness to actual value • Precision = consistency between measurements • Percent Error
How Do You CalculateAny Percentage? • The part divided by the whole times 100% • The part (your error) divided by the whole (the actual value) times 100%
Accuracy & Precision • Accuracy = closeness to actual value • Precision = consistency between measurements • Percent Error • Uncertainty in Measurement
Significant Figures in Reporting Measurements • Include one estimated digit • Applies to use of graduated cylinders, thermometers, quad-beam balances, etc.
Determining Whether Digits in a Reported Value are Significant • See Rules on Page 66-67
Determining Whether Digits are Significant • See Rules on Page 66-67 • OR follow my Atlantic/Pacific memory aid.
Determining Whether Digits are Significant • See Rules on Page 66-67 (or Atlantic-Pacific memory aid) • See Rules on rounding, pg 68. • Sig Figs in Calculations
Significant Figures In Math Operations • Addition & Subtraction
Addition and Subtraction • I weigh 74 kg (74,000 grams) • How much would I weight after eating an M&M that weighed .9687 grams? • I would still weigh 74 kg (74,000 grams)
Significant Figures In Math Operations • Addition & Subtraction • Multiplication & Division • The rules are different!
Multiplication and Division (98.34) * (62.3) * (18) = what value? 110278.476 according to my calculator – What is the correctly reported value? 110,000 is what should be reported!
Significant Figures In Math Operations • Addition & Subtraction • Multiplication & Division • Effect of Conversion Factors…or • Of Defined or counted quantities
Defined Quantities andCounted Quantities • These are considered to have an infinite number of significant digits • They therefore do not effect the number of significant digits in a calculation
Direct Proportions • y is proportional to x • y x • Dividing one by the other gives a constant
Inverse Proportions • y is proportional to the inverse of x • y 1 ÷ x • Multiplying them gives a constant
3.2The International System of UnitsEssential Question • What are the base units of the SI system, and how are they used with prefixes used to express measurements of length, volume, mass, temperature and energy?
Units of Measurement • Measuring with SI Units • Units and Quantities • SI Derived Units
SI Measurement • Seven Base Units
Units of Length • Base unit = meter (m) • Other units include centimeter, decimeter and kilometer.
Units of Volume • Liter (L) – also called the dm3 • Milliliter – also called the cm3
Units of Mass • Base unit = kilogram (kg) • Common units include the kilogram, gram, milligram and microgram.
Mass vs Weight • Mass is a measure of the amount of substance. • Weight is a measurement of the force of gravity pulling on something.
Units of Temperature • A measure of average kinetic energy. • Two Common Units of Temperature: • Degree Celsius • Kelvin • How do these two compare?
Units of Energy • The Joule (J) • The calorie (cal) and Calorie (kcal) • How do they compare? • 1 J = 0.2390 cal • 1 cal = 4.184 J
SI Derived Units • Combinations of Base Units • Volume = cm3 or dm3 • Density = m/V
3.3Conversion Problems • How is dimensional analysis useful in conversion problems?
Conversion Factors • Any number times 1 • Any number ÷ by itself • CF Don’t change VALUE, only the UNIT
SI Prefixes • 1 Millionth of Mouth Wash • 1 Million Phones • 10 cards • 2000 Mocking Birds • Time from “slip to hit”
3.4DensityEssential Question: • What determines the density of a substance, and how does temperature affect density?
Density • Determining Density • Density and Temperature