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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