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CHEMISTRY

CHEMISTRY. July 31 st , 2012. Brain Teaser: Dollar Bill. 2. What do think will happen if I dip a dollar bill in a 50% ethanol solution and light it on fire? Why? Demo Record Observations Was your prediction correct? Explain the science behind this. Agenda. 3. Brain Teaser

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CHEMISTRY

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  1. CHEMISTRY July 31st, 2012

  2. Brain Teaser: Dollar Bill 2 • What do think will happen if I dip a dollar bill in a 50% ethanol solution and light it on fire? Why? • Demo • Record Observations • Was your prediction correct? • Explain the science behind this

  3. Agenda 3 • Brain Teaser • Demo: Dollar Bill • Lecture: • Introduction to Chemistry • SI Units and Base Units • Significant Figures • Homework • Intro to Measurement Worksheet

  4. Unit 1 ObjectivesIntroduction to Chemistry 4 • Define chemistry and matter • Units of measurement • SI Units • Base Units • Accuracy versus Precision • Uncertainty in Measurement • Significant Figures

  5. Chemistry is the science that investigates and explains the structure and properties of matter. • Seeks to explain the submicroscopic events that lead to macroscopic observations Introduction to Chemistry 5 • Chemistry: The Central Science

  6. Branches of Chemistry 6

  7. SI Units (Le Systéme Internationale) Units of measurement 7 • Scientists need to report data that can be reproduced by other scientists. They need standard units of measurement. Base Units • A base unit is a defined unit in a system of measurement • There are seven base units in SI.

  8. Base Units 8

  9. 9

  10. SIGNIFICANT FIGURES 10

  11. Digits in a measurement that have meaning relative to the equipment being used Significant Figures 11 • Significant Figures

  12. What is the increment on the equipment? What you know for sure. Significant Figures 12 • Place

  13. Digits that can be known precisely plus a last digit that must be estimated. Significant Figures 13 • Digits with meaning

  14. 14

  15. Ruler 15 • http://www.funbrain.com/measure/ • What are the units?

  16. Graduated Cylinder 16 • http://www.uwplatt.edu/chemep/chem/chemscape/labdocs/catofp/measurea/volume/gradcyl/gradcyl.htm • What are the units?

  17. Depends on type of equipment being used. Depends on size of equipment used. Significant Figures 17 • What do you notice?

  18. All digits 1-9 are significant. • Zeros between significant digits are always significant. • Trailing 0’s are significant only if the number contains a decimal point • Zeros in the beginning of a number with a decimal point are not significant. • Zeros following a significant number with a decimal are significant. Significant Figures 18 • Raw Data Rules • How do you know how many sig figs?

  19. Pacific = Decimal Present Start from the Pacific (left hand side), every digit beginning with the first 1-9 integer is significant 20.0 = 3 sig digits 0.00320400 = 6 sig digits 1000. = 4 sig digits Significant Figures 19 • Pacific to Atlantic Rule • Examples

  20. Atlantic = Decimal Absent Start from the Atlantic (right hand side), every digit beginning with the first 1-9 integer is significant 100020 = 5 sig digits 1000 = 1 sig digits Significant Figures 20 • Atlantic Rule to Pacific • Examples

  21. Practice 21 • How many significant figures are in • 400.0 • 4000 • 4004 • 0.004

  22. Rally Rows 22 How many significant figures are in • 0.02 • 0.020 • 501 • 501.0 • 5000 • 5000. • 5050 • 01.0050 • 50300 • 5.0300

  23. Review Questions 23 • Determine the number of significant figures in the following: • 1005000 • 1.005 • 0.000125 • 1000. • 0.02002 • 2002 • 200.200

  24. Review Questions 24 Determine the number of significant figures in: • 72.3 g • 60.5 g • 6.20 g • 0.0253 g • 4320 g • 0.00040230 g • 4.05 x 10^5 g • 4500. g

  25. Why do we use the metric system? 25 • Advantages • Simple to use • Easy to convert from one unit to another • Dimensional Analysis • Universal – used worldwide • By all scientists to communicate • By all industrialized nations • Except United States • U.S. loses billions of dollars in trade

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