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Scientific Measurements

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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  1. Scientific Measurements

  2. 3.1Measurements andTheir UncertaintyEssential Question • How do scientists accurately and precisely report measured quantities?

  3. Scientific Notation • Form M x 10n • Rules for Addition & Subtraction • Rules for Multiplication • Rules for Division

  4. Measurements and Uncertainty • Accuracy and Precision • Significant Figures • Direct Proportions • Indirect Proportions

  5. Accuracy & Precision • Accuracy = closeness to actual value • Precision = consistency between measurements • Percent Error

  6. 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%

  7. Accuracy & Precision • Accuracy = closeness to actual value • Precision = consistency between measurements • Percent Error • Uncertainty in Measurement

  8. Significant Figures in Reporting Measurements • Include one estimated digit • Applies to use of graduated cylinders, thermometers, quad-beam balances, etc.

  9. Determining Whether Digits in a Reported Value are Significant • See Rules on Page 66-67

  10. Determining Whether Digits are Significant • See Rules on Page 66-67 • OR follow my Atlantic/Pacific memory aid.

  11. Atlantic-Pacific Memory Aid

  12. 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

  13. Significant Figures In Math Operations • Addition & Subtraction

  14. 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)

  15. Significant Figures In Math Operations • Addition & Subtraction • Multiplication & Division • The rules are different!

  16. 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!

  17. Significant Figures In Math Operations • Addition & Subtraction • Multiplication & Division • Effect of Conversion Factors…or • Of Defined or counted quantities

  18. 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

  19. Direct Proportions • y is proportional to x • y  x • Dividing one by the other gives a constant

  20. Inverse Proportions • y is proportional to the inverse of x • y  1 ÷ x • Multiplying them gives a constant

  21. 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?

  22. Units of Measurement • Measuring with SI Units • Units and Quantities • SI Derived Units

  23. SI Measurement • Seven Base Units

  24. Units of Length • Base unit = meter (m) • Other units include centimeter, decimeter and kilometer.

  25. Units of Volume • Liter (L) – also called the dm3 • Milliliter – also called the cm3

  26. Units of Mass • Base unit = kilogram (kg) • Common units include the kilogram, gram, milligram and microgram.

  27. Mass vs Weight • Mass is a measure of the amount of substance. • Weight is a measurement of the force of gravity pulling on something.

  28. Units of Temperature • A measure of average kinetic energy. • Two Common Units of Temperature: • Degree Celsius • Kelvin • How do these two compare?

  29. 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

  30. SI Derived Units • Combinations of Base Units • Volume = cm3 or dm3 • Density = m/V

  31. 3.3Conversion Problems • How is dimensional analysis useful in conversion problems?

  32. Conversion Factors • Any number times 1 • Any number ÷ by itself • CF Don’t change VALUE, only the UNIT

  33. Conversion FactorsSee Figure 3.11Page 81

  34. SI Prefixes

  35. SI Prefixes • 1 Millionth of Mouth Wash • 1 Million Phones •  10 cards • 2000 Mocking Birds •  Time from “slip to hit”

  36. 3.4DensityEssential Question: • What determines the density of a substance, and how does temperature affect density?

  37. Density • Determining Density • Density and Temperature

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