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Scientific method

Scientific method. Method for answering questions Make an observation Ask a question (hypothesis) Obtain facts (experiment) Explain experiment (conclusion) Theory or law. Measurements – SI units. Metric prefixes. Derived units. Area L x w Volume L x w h

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Scientific method

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  1. Scientific method Method for answering questions • Make an observation • Ask a question (hypothesis) • Obtain facts (experiment) • Explain experiment (conclusion) • Theory or law

  2. Measurements – SI units

  3. Metric prefixes

  4. Derived units • Area • L x w • Volume • L x w h For more see appendix p 806 Agenda p R-11

  5. Reliability • Precision ability to repeat measurement • Accuracy ability to get accepted value • Bulls eye

  6. Uncertainty in Measurement • Measurements involve estimation in last digit • Remember …..

  7. Significant digits • The certain and 1 estimated digit of a measurement • Atlantic-Pacific rule if a decimal is Absent, count first non-zero number from Atlantic side if a decimal isPresent, count first non- zero number from the Pacific side

  8. Practice How many significant figures in each? • .00987 • 98700 • 987.00 • 98700987 • 987.00987 3 3 5 8 8

  9. Calculations • Addition/subtraction count least places after the decimal • Multiplication/division count the least number of significant digit

  10. Practice Calculations • 2.3 x 11.0090= • 15.00 = 3.7 • 11 + 2.34 + 900.0560= • (3.2 x 103)(6.003 x 10-2)= • 8.90 x 106 = 5.1 x 10 -9

  11. Problem Solving • 1. Write known and unknown • 2. Write equation • 3. Use factor label method (start with the units of the known) • 4. Calculate • 5. Circle answer with correct significant figures

  12. Ratios • Speed Distance time • Density mass volume

  13. Ratios of equal terms • 1 m = 10 dm 1m10 dm 10 dm 1m • 1 min = 60 sec 1 min60 sec 60 sec 1 min For more see agenda p R-10

  14. Factor label=Dimensional AnalysisUsing units to solve problems Show work using units 1.   How many seconds in 14 days? Show work. 2. How many mL in 1.09 kL? 3. Convert 3.4 g/ml to dg/cL

  15. Graphs • Create a good data table

  16. Computer Graphing • Excel • A- x axis,flask size (ml) • B- Y axis, time (sec) • Highlight all 2columns • Chart Wizard • X,Y scatter middle chart, left column • Title (include your name), label both axis • New sheet • Unshade background • Print 1 to science dept

  17. Excel A- x axis (volume), B- Y axis (mass) • Highlight all 2columns, Chart Wizard • X,Y scatter top chart, left column • Title (include your name), label both axis • New sheet • Chart add trend line Linear • options tab Check off • intercept=0 • display equation chart, • Unshadebackground/format plot area/white box • Print to lexchex or sci dept

  18. Slope Rise = y2-y1 = m2-m1 = mass Run x2-x1 v2-v1 volume Pick 2 points on the line. Write the coordinates (x1,y1)(x2,y2) Calculate the density Do this on your graph.

  19. Pure Matter Elements cannot be broken down by chemical processes Compound Chemical combination of elements (share or transfer of electrons)

  20. States of Matter • Gas • Liquid • Solid • Plasma

  21. What’s the Difference? Gases are almost random Solids are ordered Liquids have Some order

  22. MatterAnything that has mass and volume do not copy in notebook Density PressureContainer Solid High not affected own shape Liquid High not affected takes shape Gas low affected fills Plasma low affected fills

  23. Changes in Matter • Physical changes Involve no change in composition Physical properties: Boiling/melting point, density, color, odor, ductile • Chemical changes • Involves a change in composition Heat change Color change Gas evolved Precipitate formed Chemical properties: combustion, reactivity

  24. Changes of State • What is happening to the molecules as ice heats up? Change from one state to another takes energy • Is the melting point and freezing point the same? • Heat of fusion • Is the evaporation and condensation pt the same? • Heat of evaporation • What is the difference between steamed and boiled?

  25. Cooling Curve Gas Condense/evaporate Liquid Freeze/melt Solid

  26. Temperature Scales • Fahrenheit was a thermometer maker • He was a very good thermometer maker • Why do we still use his scale? • Celsius is based on the melting point and boiling point of water • 0o C = Freezing point of Swiss Alps snow • 100oC = Boiling point at sea level Why does it have to be at sea level? • Why is this better than Fahrenheit?

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