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Data Analysis

Data Analysis. Applying Mathematical Concepts to Chemistry. Accuracy- closeness of measurements to the target value Error - difference between measured value and accepted value (absolute value). Precision- closeness of measurements to each other. Accuracy vs Precision. Units of Measure.

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Data Analysis

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  1. Data Analysis Applying Mathematical Concepts to Chemistry

  2. Accuracy- closeness of measurements to the target value Error- difference between measured value and accepted value (absolute value) Precision- closeness of measurements to each other Accuracy vs Precision

  3. Units of Measure • SI Units- scientifically accepted units of measure: • Know: • Length • Volume (m3) • Mass • Density (g/mL) • Temperature • Time

  4. The Metric System

  5. Metric Practice • 623.19 hL = __________ L • 1026 mm = ___________cm • 0.025 kg = ___________mg • Online Powers of 10 Demonstration: http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

  6. Good Info to Know • Volume- amount of space an object takes up (ex: liters) • V = l x w x h • 1 cm3 = 1 mL by definition

  7. More Good Info to Know • Mass is different from weight • Mass ≠ Weight • Mass= measure of the amount of matter in an object • Weight= force caused by the pull of gravity on an object • ***Mass is constant while weight varies depending on the location of an object***

  8. Scientific Notation • concise format for representing extremely large or small numbers • Requires 2 parts: • Number between 1 and 9.99999999… • Power of ten • Examples: • 6.02 x 1023 = 602,000,000,000,000,000,000,000 • 2.0 x 10 -7 m = 0.0000002 m • Use calculator to solve problems on p. 788-789

  9. Significant Figures • Measurements are limited in their sensitivity by the instrument used to measure

  10. Estimating Measurements • Read one place past the instrument • 35.0 mL is saying the actual measurement is between 34.9 and 35.1 mL

  11. Why Significant Figures? • Measurements involve rounding • Multiplying/dividing or adding/subtracting measurements can not make them more accurate • Provide a way to tell how sensitive a measurement really is… • 5 ≠ 5.0 ≠ 5.00 ≠ 5.000

  12. Recognizing Significant Digits • 1. Nonzero digits are always significant • 543.21 meters has 5 significant figures • 2. Zeros between nonzeros are significant • 505.05 liters has 5 sig figs • 3. Zeros to the right of a decimal and a nonzero are significant • 3.10 has 3 sig figs

  13. Recognizing Sig Figs • 4. Placeholder zeros are not significant • 0.01g has one sig fig • 1000g has one sig fig • 1000.g has four sig figs • 1000.0g has five sig figs • 5. Counting numbers and constants have infinite significant figures • 5 people has infinite sig figs

  14. Rule for Multiplying/Dividing Sig Figs • Multiply as usual in calculator • Write answer • Round answer to same number of sig figs as the lowest original operator • EX: 1000 x 123.456 = 123456 = 100000 • EX: 1000. x 123.456 = 123456 = 123500

  15. Practice Multiplying/Dividing • 50.20 x 1.500 • 0.412 x 230 • 1.2x108 / 2.4 x 10-7 • 50400 / 61321

  16. Rule for Adding/Subtracting • Only place values where all measurements being added/subtracted have sig figs are utilized • EX: 1000 + 1.2345 1000

  17. Practice Adding/Subtracting • 100.23 + 56.1 • .000954 + 5.0542 • 1.0 x 103 + 5.02 x 104 • 1.0045 – 0.0250

  18. Derived Quantities- Density • Density- how much matter is in the volume an object takes up. • Density = mass/volume • D= g/mL

  19. Determining Density • Mass- measure in grams with balance • Volume- • Regular shaped object: measure sides and use volume formula • EX: rectangle  V= l x w x h • Irregular shaped object: water displacement

  20. Density by Water Displacement • Fill graduated cylinder to known initial volume • Add object • Record final volume • Subtract initial volume from final volume • Record volume of object

  21. Graphing Data How Does Volume Impact Temperature? • General Rules • Fit page • Even scale • Best fit/trendline • Informative Title • Labeled Axes

  22. Temperature Scales

  23. Degrees Celsius to Kelvin Tkelvin=Tcelsius + 273 EX: 25 °C = ? K Tkelvin=25 +273=298K Kelvin to Degrees Celsius Tcelsius=Tkelvin - 273 EX: 210 K = ? °C Tc= 273–210= -63°C Temperature Conversions

  24. Percent Error • %error = (accepted-experimental) x 100 accepted • EX: The measured mass is 5.0g. It was predicted that the accepted value should have been 6.0 g. • % error = 6.0g-5.0g x 100 = 16.7% 6.0g

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