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August 3-4, 2011
Brain Teaser QuizletOpen Note Quizlet Place Notes (Ch 2.6-2.8) on your desk
Brain TeaserWhat do you think will happen if I
light the bubbles on fire?Why?DemoRecord ObservationsWas your prediction correct?Explain the science behind it
AgendaBrain Teaser QuizletMeasurement TermsNumbers Notes:
SI UnitsIntro to Significant FiguresMeasurement and Significant Figures Mini LabScientific Notation
HomeworkSignificant Figures WorksheetQualitative and Qunatitative WorksheetBlubbenbacher’s Foods Lab Report Due This
Friday
Data TermsQuantitative
Measurements
Examples
Give results in a definite form, usually values
24L, 10 cm, 14 ºC
Data TermsQualitative
Measurements
Examples
Give results in a descriptive, non-numeric form.
The beaker was warm.The density was greater
than that of water.
Data TermsAccuracy
Examples
How close a measurement comes to the actual value of whatever is being measured
Water freezes at 0º C, and boils at 100º C. How close is the measurement to the values.
Data TermsPrecision
Examples
Reproducibility of the measurement
9 out of 10 lab groups report the temperature of boiling water to be 95º C.
A basketball player shoots 20 free throws, 18 of which bounce off the right side of the rim.
Accuracy vs. PrecisionTarget Practice
Accurate Precise Accurate & Precise
Percent errorTheoretical – Experimental x 100 = % error
Theoretical
ClosureGive and example of a qualitative and
quantitative measurement.
SI Units (Le Systéme Internationale)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.
Refer to the handout on SI Units
Units of measurement
Base Units
Significant FiguresSignificant
FiguresDigits in a measurement that
have meaning relative to the equipment being used
Significant FiguresPlace What is the increment on the
equipment?
What you know for sure.
Significant FiguresDigits with
meaning
Examples
Digits that can be known precisely plus a last digit that must be estimated.
Refer to Examples on the board:
1.2.3.4
Scale Reading and UncertaintyUncertainty: Limit of precision of the reading
(based on ability to guess the final digit). Existed in measured quantities versus counted
quantitiesRefer to Example (2 rulers)
Significant Figures: Mini LabEquipment to EvaluateTo what place
(tenths, hundredths, etc.) can these measurement instruments accurately measure? What place is the estimation?
Triple beam balanceAnalytical balanceThermometerGraduated cylindersBeakersRulerBurette
Significant FiguresWhat do you
notice?Depends on type of
equipment being used.Depends on size of
equipment used.
Significant FiguresRaw Data Rules
How do you know how many sig figs?
1. All digits 1-9 are significant.2. Zeros between significant
digits are always significant.3. Trailing 0’s are significant
only if the number contains a decimal point
4. Zeros in the beginning of a number with a decimal point are not significant.
5. Zeros following a significant number with a decimal are significant.
Significant FiguresPacific to
Atlantic Rule
Examples
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 digits0.00320400 = 6 sig digits1000. = 4 sig digits
Significant FiguresAtlantic Rule
to Pacific
Examples
Atlantic = Decimal Absent Start from the Atlantic
(right hand side), every digit beginning with the first 1-9 integer is significant
100020 = 5 sig digits1000 = 1 sig digits
Practice How many significant figures are in1. 400.02. 40003. 40044. 0.004
Rally Rows How many significant figures are in1. 0.022. 0.0203. 5014. 501.05. 50006. 5000.7. 50508. 01.00509. 5030010. 5.0300
SummaryThings to considerWhat do significant figures tell you about the measurement
equipment?
If you wanted to measure the mass of a whale, what scale would you want to use? Would it matter if you know its mass accurately to 1 gram?
If you wanted to measure the mass a grain of sand , what scale would you want to use? Would it matter if you know its mass accurately to 1 gram?
Instrument MeasureNeed to make sure you are measuring and
recording to the correct number of digitsMeasure what you know for sure and then
guess one more digitRulers
Draw a line on your paper and measure it to the correct number of digits
Beaker vs. graduated cylinderElectronic balance vs. triple beam balance
Scientific NotationScientific
Notation
Example
Shorthand way of expressing numbers that make them easier to work with
6.02 x 1023
2.34 x 105
3.78 x 10-3
Scientific NotationAny Patterns?
Scientific NotationRules 1. Base number 1-9
2. Exponent = the number of times the decimal must be moved to bring the base number to 1-9.
3. Numbers greater than 1 have a positive exponent, numbers less than 1 a negative exponent
Scientific NotationExamples
0.0025
1,750,000
2.5 x 10-3
1.75 x 106
Scientific NotationProblems
Express in Scientific Notation
0.0000678
998953000000
0.5768
Scientific NotationProblems
Express in Standard Notation
1.567 x 10-3
6.02 x 1023
3.14 x 102
Sig Figs in Scientific NotationThe numbers expressed in the scientific
notation are significantExamples: 5.02 x 104 5.02 x 104 3 S.F
The number of significant figures in a set of numbers will be the # of sig figs in the scientific notation.
Examples: 50.200 5 SF 5.0200 x 101
Survivor Science Convert the following to exponential
notation or to ordinary notation Tell me how many Sig Figs.
1. 762. 8967453. 8.9 x 103
4. 3.45 x 10-1
5. 0.222
6. 5.38 x 10-3
7. 5 million8. 8.00 x 104
9. 0.0085910. 953.6
Significant Figures in CalculationsWhat are
Significant Digits?
ExamplesTriple
Beam Balance
Graduated Cylinder
All the certain digits plus the estimated digit in a measurement.
How many decimal places can we count
Significant Figures in CalculationsExact
Numbers
ExamplesInfinite #
of sig figs
Do not affect the number of significant digits in the final answer. They are not measurements!!
1000m = 1 km12 in = 1 foot
Significant Figures in CalculationsMultiplication
and Division
Example
The number with the smallest number of significant digits determines how many significant digits are allowed in the final answer.
Volume of a box L x W x H(3.05m)(2.10m)(0.75m)2 sig figs4.8m3
Significant Figures in CalculationsExample
Density of a penny
M = 2.53g V = 0.3mL
D = M / V# significant figures
allowedD = 8g/mL
Significant Figures in CalculationsAddition
and Subtraction
Example
The number of significant digits depends on the number with the largest uncertainty. (you may be using different scales)
Shoes 951.0 gClothes 1407 gRing 23.911 gGlasses 158.18 gTotal 2540. g
Significant Figures in CalculationsExample What is the mass of a penny
if, the weighing paper alone has a mass 0.67 g and weighing paper plus the penny has a mass of 3.2 g.
3.2 g -0.67 g
2.5 g
Significant Figures in CalculationsRemember A calculated number can only
be as precise as the least precise measurement in the calculation.
PracticeCalculate each of the following to the correct
number of significant figures. Include units on your answer.
1. (25 g/mol)(4.0 mol) =2. (3.48 in)(1.28 in)(0.010 in) = 3. 2.06 cm + 1.8 cm + 0.004 cm = 4. If the mass of a lead cube is 176.91 g and it
measures 2.51cm x 2.49 cm x 2.49 cm, what is the density of lead?
PracticeCalculate each of the following to the correct
number of significant figures. Include units on your answer.
1. (25 g/mol)(4.0 mol) =1.0 x 101.0 x 1022
2. (3.48 in)(1.28 in)(0.010 in) = .045 in.045 in33
3. 2.06 cm + 1.8 cm + 0.004 cm = 3.9 cm3.9 cm4. If the mass of a lead cube is 176.91 g and it
measures 2.51cm x 2.49 cm x 2.49 cm, what is the density of lead? 11.3 g/cm11.3 g/cm33
Rally rowsSig figs in Calculations1. 12 cm + 0.031cm + 7.969 cm =2. (41.025 g - 23.38g) ÷ 8.01 mL=3. 17.3 cm x 6.2 cm + 3.28 cm2 = 4. 109.3758 m2 45.813 m =5. What is the mass of Salt (NaCl) if the
sodium has a mass of 22.99 g and the Cl a mass of 35.5g?
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