# Scientific method

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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
Transcript
• Make an observation
• Obtain facts (experiment)
• Explain experiment (conclusion)
• Theory or law
• Measurements – SI unitsMetric prefixesDerived units
• Area
• L x w
• Volume
• L x w h
• For more see appendix p 806Agenda p R-11Reliability
• Precision
• ability to repeat measurement
• Accuracy
• ability to get accepted value
• Bulls eye
• Uncertainty in Measurement
• Measurements involve estimation in last digit
• Remember …..
• 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 sidePracticeHow many significant figures in each?
• .00987
• 98700
• 987.00
• 98700987
• 987.00987
• 33588Calculations
• count least places after the decimal
• Multiplication/division
• count the least number of significant digitPractice 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 -9Problem 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
• Ratios
• Speed
• Distance time
• Density
• mass volumeRatios of equal terms
• 1 m = 10 dm
• 1m10 dm 10 dm 1m
• 1 min = 60 sec
• 1 min60 sec 60 sec 1 minFor more see agenda p R-10Factor label=Dimensional AnalysisUsing units to solve problemsShow work using units1.   How many seconds in 14 days? Show work.2. How many mL in 1.09 kL?3. Convert 3.4 g/ml to dg/cLGraphs
• Create a good data table
• 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
• Print 1 to science dept
• ExcelA- 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
• options tab Check off
• intercept=0
• display equation chart,
• Print to lexchex or sci dept
• SlopeRise = y2-y1 = m2-m1 = mass Run x2-x1 v2-v1 volumePick 2 points on the line. Write the coordinates (x1,y1)(x2,y2)Calculate the density Do this on your graph. Pure MatterElementscannot be broken down by chemical processesCompoundChemical combination of elements (share or transfer of electrons)States of Matter
• Gas
• Liquid
• Solid
• Plasma
• What’s the Difference?Gases are almostrandomSolids are orderedLiquids haveSome orderMatterAnything that has mass and volumedo not copy in notebookDensity PressureContainerSolid High not affected own shape Liquid High not affected takes shapeGas low affected fillsPlasma low affected fillsChanges in Matter
• Physical changes
• Involve no change in compositionPhysical properties:Boiling/melting point, density, color, odor, ductile
• Chemical changes
• Involves a change in composition
• Heat changeColor changeGas evolvedPrecipitate formedChemical properties:combustion, reactivityChanges 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?
• Cooling CurveGasCondense/evaporateLiquidFreeze/meltSolidTemperature 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?
• Related Search
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