22 Sept. 2010

22 Sept. 2010

Take out homework: Week 2/3 Homework p. 3 Analysis for graphs

Objective: SWBAT determine the precision and accuracy of data.

Do now: Imagine you are a very accurate shot with a bow and arrow. Draw a picture to show what your target looks like at the end of practice.

Agenda

1. Do now2. Go over HW: Analysis of graphs3. Notes and examples of precision and

accuracyHomework: Week 2/3 Homework p. 3 Conclusions: Fri. Conclusion for Density of Pennies Lab: Fri. Week 3 Homework: Fri. Lab report: Weds.

SWBAT determine the precision and accuracy of data.

Precision and Accuracy

precision: how close a series of measurements are to each other.

accuracy: how close a series of measurements are to the actual or true value.



Volume of a sample of water(Actual volume: 5 mL)

a. 2.0 mL, 2.1 mL, 1.9 mLb. 4.0 mL, 5.0 mL, 6.0 mLc. 1.2 mL, 5.5 mL, 10.6 mLd. 4.9 mL, 5.0 mL, 5.0 mL


Mass of copper cylinder (g)

Danika Josh LarissaMassing 1

47.45 47.95 47.13

Massing 2

47.39 47.91 47.94

Massing 3

47.42 47.89 46.83

Massing 4

47.41 47.93 47.47Three students made multiple weightings of a copper cylinder, each using a different balance. The correct mass of the cylinder had previously been determined to be 47.32 grams. Comment on the accuracy and precision of each student’s measurements.SWBAT determine the precision and accuracy of data.

Comment on the accuracy and precision of these basketball free-throw shooters: a. 99 of 100 shots are made b. 99 of 100 shots hit the front of

the rim and bounce off c. 33 of 100 shots are made, the

rest miss.


Percent Error: a measurement of how accurate your data are

100_

__

valueactual

valueactualvalueyour

1. So, if the actual value is 5.0 grams, but your average mass was 4.6 grams, what is your percent error?

2. What if your average volume was 25.0 mL, but the actual value is 23.9?

Homework

Week 2/3 Homework p. 3 Conclusions: Fri.

Conclusion for Density of Pennies Lab: Fri.

Week 3 Homework: Fri. Lab report: Weds.

24 Sept. 2010

Take out homework: Week 3 HW Objective: SWBAT convert between units

in the SI system and review for a quiz! Do now: My actual mass is 59.1 kilograms.

I weighed myself on three different scales at the gym, and got the following masses: 64.9, 65.0 and 65.2 kg. Are these masses accurate, precise, both

or neither, and WHY?

Agenda

I. Do nowII. Homework Check: Week 3 HWIII. Converting SI unitsIV. Review StationsHomework:Finish Week 2/3 HomeworkQuiz Monday.Bring your book!! (see me after school if

you need a book)

Converting between SI units

notes from the board

SWBAT convert between units in the SI system.

SI Unit Prefixes

Steps to Conversions

1. Identify and write your known and unknown.

2. Choose an equality.3. Make a fraction4. Put units to cancel on the bottom5. Put units to remain on the top6. Cancel units and compute7. Report answer with units!

Practice Problems

1 liter = 1000 milliliters1. How many liters are equal to 550

milliliters?2. How many milliliters are equal to 3.5

liters?3. How many liters are equal to 45,000

milliliters?4. How many milliliters are equal to 354

liters?SWBAT convert between units in the SI system.

1 meter = 100 cm, 1 kilometer = 1000 meters1. How many meters are equal to 500

centimeters?2. How many centimeters are equal to 850

meters?3. How many meters are equal to 37.5

kilometers?4. How many centimeters are equal to 5.8

kilometers?


Homework

Finish Week 2/3 HomeworkQuiz tomorrowBring your book!! (see me after

school if you need a book) Lab report: Weds.


23 Sept. 2010

Take Out: Week 2/3 HomeworkYou need a calculator and your book. Objective: SWBAT show what you

know about Thinking Like a Scientist.

Do now: How many meters are equal to 37.5 kilometers?

(1 kilometer = 1000 meters)

Agenda

I. Do nowII. Homework CheckIII. QuizIV. Physical properties and changes:

textbook readingHomework: Finish Textbook Analysis

Classwork and Homework: Mon.Lab Report: Tues.

Quiz Expectations

Work silently and on your own. Raise your hand if you have

questions. When you finish, flip your quiz over. Begin working on the textbook

analysis classwork.

Homework

Finish Textbook Analysis Classwork and Homework: Mon.

Lab Report: Tues.Please bring a calculator EVERY day!

24 Sept. 2010

Grab your clicker!Take Out Homework: Textbook

AnalysisObjective: SWBAT identify and round

a number to the correct number of significant figures.

Do now: What is the difference between chemical and physical changes?

SWBAT identify and round a number to the correct number of significant figures.

Agenda

I. Do nowII. Homework checkIII. Notes: Significant FiguresIV. Practice ProblemsV. Conversions problems with

significant figuresHomework: Sig. Fig. and Rounding

WorksheetLab report: Tues. (typed)


An engineer was responsible for calculating amount of water that overflowed from a dam. He measured all of the water runoff going into the reservoir (1.2 million cubic feet per year), the rainfall (860 cubic feet per year), and the capacity of the reservoir (3.8 million cubic feet). He did some fancy calculations. He reported to his boss that the overflow from the dam would be 350,246.2544330 cubic feet per year.

What’s wrong here?


SIGNIFICANT FIGURESRules for determining how many digits to round to

I. Significant Figuresaka: Significant Digits

A. Nonzero integers count as significant figures Ex. Any number that is NOT zero (1, 2, 3, 4,

5, 6, 7, 8, 9) 345 597.2 145.456


Zeros B. Leading zeros that come before all the

nonzero digits do NOT count as significant figures

Ex: 0.0025 has two sig. fig. The zeros are “leading” and do not count.

0.23 0.0004 0.03564


C. Captive zeros are between nonzero digits and DO count as sig. fig.

Ex: 1.008 has four sig. fig. The zeros are captive and DO count.

10,004 1.000006 1,000,000,000,000,567


D. Trailing zeros are to the right end of the number and DO count as sig. fig. if the number contains a decimal point.

Ex.: 100 has only one sig. fig. because the trailing zeros DO NOT have a decimal point.

Example: 1.00 has three sig. fig. because the trailing zeros DO have a decimal point.

1.000000 3,000,000 3.00000 30.00 300 300.


E. Exact numbers Any number found by counting has an

infinite number of significant figures. Ex: I have 3 apples. The 3 has an infinite

number of significant figures. 50 people 100 baseballs


Which are exact numbers?

1. The elevation of Breckenridge, Colorado is 9600 feet.

2. There are 12 eggs in a dozen.3. One yard is equal to 0.9144 meters.4. The attendance at a football game was

52,806 people.5. The budget deficit of the US

government in 1990 was $269 billion.6. The beaker held 25.6 mL of water.


How many significant figures? 256

1 2 3 4

6%0%

94%

0%

1. 12. 23. 34. 4


How many significant figures? 647.9

1 2 3 4

0%

100%

0%0%

1. 12. 23. 34. 4



1 2 3 4

0%

83%

17%

0%

1. 12. 23. 34. 4



1 2 3 4

0%

89%

5%5%

1. 22. 33. 44. 5


How many significant figures? 4005

1 2 3 4

0%

95%

0%5%

1. 12. 23. 34. 4


How many significant figures? nine

1 2 3 4

10%

90%

0%0%

1. 12. 23. 34. infinite


How many significant figures? 200.

1 2 3 4

6%0%

94%

0%

1. 12. 23. 34. 4



1 2 3 4

0%

85%

15%

0%

1. 12. 23. 34. 4



1 2 3 4

5%

25%

10%

60%1. 22. 43. 64. 7


How many significant figures? -500

1 2 3 4

74%

0%

26%

0%

1. 12. 23. 34. 4


How many significant figures? -500.

1 2 3 4

5%0%

89%

5%

1. 12. 23. 34. 4


How many significant figures? 1.3x1032

1. 12. 23. 34. 4


How many significant figures?

1. A student’s extraction procedure yields 0.0105 g of caffeine.

2. A chemist records a mass of 0.050080 g in an analysis.

3. In an experiment, a span of time is determined to be 8.050 x 10-3 s.

4. Rewrite 8.050 x 10-3 so it has three significant figures.


So how do we use this new skill?

To determine how many digits to round do after making a calculation.

Ex 1: How many liters are equal to 34,500 milliliters?

Ex 2: How many milligrams are equal to 3,000.0 grams?

Ex 3: How many centimeters are equal to 12.000 meters?


Complete the Sig. Fig. and Rounding Worksheet


Homework

1. Sig. Fig. and Rounding Worksheet2. Lab report: Tues. (typed)


The sample of gold contained 1,200,000,000,000,000,000,000,000,000 atoms.

How do we keep track of ALL those zeros?

In chemistry, some numbers are HUGE!

II. Scientific Notation(aka: Exponential Notation)

8,000,000 = 0.00012 = Integer must be 1≤x<10

Positive exponent: number > 1 Negative exponent: number < 1 (but >

0!)

4,500,000 3,950,000,000 230 230. 0.00000045 -0.002 0.00781

Copy the number and rewrite in scientific notation

a. 100,000b. -5,000,000c. 450,000,000,000d. 1,300e. 0.01f. 0.00 005g. -0.0 045h. 0.00 000 000 000 000 023

Remember…

A negative exponent is a tiny number but is bigger than 0 (NOT a negative number!)

A big exponent is a HUGE number. A negative number can have either a

positive exponent or a negative exponent.

Round to three sig. fig. and express in exponential notation.

1. 745,0002. 0.000540003. 540,321,3244. 0.143589

Homework

Handout: Significant Figures and Scientific Notation

III. Rules for Sig. Fig. in Mathematical Operations

A. Multiplication and Division The number of sig. fig. in the results should

be the same as the number of sig. fig. in the least precise measurement used in the calculation.

Example: 4.56 x 1.4 = 6.38 6.4

B. Addition and Subtraction The result should have the same number of

decimal places as the least precise measurement used in the calculation.

Example: 12.11 + 18.0 + 1.013 = 31.123 31.1 (one decimal place)

13 x 1.000 = 13.000 = 23.45 x 400 = 9380 = 5000 / 3.12 = 1602.56410256…

14 + 3.567 = 17.567

56.2 + 23.988 = 80.188

100 – 1.9995 = 98.0005

IV. Rounding

Calculate first, then round Example: round 4.348 to two sig. fig.

4.3 Never round until your final answer!

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22 Sept. 2010