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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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## Scientific Measurements

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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

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