C: 22 September 2011

Take Out Homework: W eek 3 #1-5 and Lab Report

Objective: You will be able to: differentiate between accurate and

precise measurements determine the number of significant

figures in any value Do now: Calculate the mass of a pure

copper penny (density = 8.92 g/cm3) with a volume of 0.20 cm3.

Agenda

I. Do nowII. Track objective masteryIII. Go over homeworkIV. Accuracy vs. precision notes and

examplesV. Practice problemsVI. Significant figures rules and examplesVII. Clicker practice problemsHomework: Week 3 Homework #6-10: Fri.

Track Objective Mastery

Objective 8 (Density) Exit Ticket Unit 1 Pretest B Objectives 5-12

Where have you improved most?!

Density Exit Ticket

II. b. Calculate the volume of a piece of gold (density = 19.32 g/cm3) that has a mass of 5.00 grams.

Expectations

During notes and example problems: silently write them into your notebook Raise your hand to ask questions

or make comments

Reading a graduated cylinder

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)

Larissa Loveng LorrenoMassing 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 weighings 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.

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.

SWBAT determine the precision and accuracy of data.

On Your Own

a. How are accuracy and precision similar?

b. How are accuracy and precision different?

c. Give an example of a data set that is very precise but not accurate. (Hint: You’ll have to write down the “real” answer, too.)

Percent Error: a measurement of how accurate your data are

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?

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 Figures

How to determine how accurate a number is

How to determine how much to round an answer

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

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

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.

More practice: Trailing zeros

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.

Clicker Use

Always pick up and use only your assigned clicker: You are responsible for it!

Remain silent while the question is being read and while you answer – only answer for yourself!

Never laugh at, mock or ridicule the proportion of students answering incorrectly.

Listen carefully as the answer is explained.

How many significant figures? 256

1 2 3 4

1. 12. 23. 34. 4

How many significant figures? 647.9

1 2 3 4

1. 12. 23. 34. 4

1 2 3 4

1. 12. 23. 34. 4

1 2 3 4

1. 22. 33. 44. 5

How many significant figures? 4005

1 2 3 4

1. 12. 23. 34. 4

How many significant figures? nine

1 2 3 4

1. 12. 23. 34. infinite

How many significant figures? 200.

1 2 3 4

1. 12. 23. 34. 4

1 2 3 4

1. 12. 23. 34. 4

1 2 3 4

1. 22. 43. 64. 7

How many significant figures? -500

1 2 3 4

1. 12. 23. 34. 4

How many significant figures? -500.

1 2 3 4

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.

Assignment

In your lab notebook, find the density stations from yesterday.

Next to each value you measured, write the number of significant figures in a circle. Ex: 12.35 cm 4

Exit Ticket

Homework

Week 3 Homework #6-10: Fri.

RoundingTake Out Homework: Week 3 Homework

#1-10 Objective: You will be able to:

round values to the correct number of significant figures

Do now: How many significant figures? a. 0.00045 b. 0.00040 c. 0.0004050

Agenda

I. Do nowII. Go over homeworkIII. Accuracy/Precision, Sig. Fig. “Exit”

TicketIV. Rounding Notes and ExamplesV. Practice ProblemsVI. Exit TicketHomework: Week 3 Homework #11-14:

“Exit” Ticket

Precision/Accuracy Sig. Fig.

Rounding

The answer to a calculation can not be any more accurate than the least accurate value in that calculation.

When multiplying or dividing, round to the least number of significant figures given in the problem.

Example 1

An iron block with side lengths 10.5 cm by 22.6 cm by 2.5 cm has a mass of 4655 grams. Calculate the density of iron.

Example 2

The density of mercury is 13.53 g/cm3. Calculate the volume taken up by 5.0 grams of mercury.

Problems

1. Calculate the mass of a cube of silver with side length 5.0 cm. Silver has a density of 10.49 g/cm3.

2. Calculate the density of a stack of gold coins with mass 1100 grams and volume of 51.76 cm3.

Exit Ticket

Rounding

Homework

Week 3 Homework #11-14: Monday

Objective: You will be able to: round a calculation to the correct

number of sig. fig. plan a procedure and data table

for a lab on the density of pennies Do now: Round to TWO sig. fig:

a. 0.003563725b. 5,723

Agenda

I. Do nowII. Tracking Objectives – RoundingIII. Rounding WorksheetIV. Pennies lab: Plan procedureV. Design a data tableHomework: Quiz Friday: Objectives

Tracking Objectives

Rounding Exit Ticket: Objective 11

Rounding Practice (10 min.)

Quietly, on your own If you have a question, you may

consult your partner or raise your hand to ask me a question.

When you are done, have me check your work.

Then, complete the exit ticket on your own.

With your lab group (20 min.)

In your notebook: Copy the research questions Make two hypotheses (one for

each research question) On the poster paper as a group:

Write your complete and detailed procedure

Gallery Walk (8 min.)

With a marker, read another group’s procedure.

Make constructive comments in writing “How big is the graduated

cylinder?” “I like how you were specific about

what to change in each trial!” Then, visit another group’s poster

and do the same thing.

Together:

Construct the procedure we will all follow from the best elements of everyone’s group posters.

As a lab group

Design your data table for next class!

Homework

Quiz Friday: Objectives 8-11 Finish Procedure

A: 27 September 2011

Objective: You will be able to: determine the relationship between

mass and volume of pennies. compare the density of pre- and

post-1982 pennies. Do now: Round to THREE sig. fig:

a. 0.003549248b. 356,908,256

Agenda

I. Do nowII. Tracking ObjectivesIII. Carry out your procedure and collect

data!IV. Finish calculationsHomework: Finish Unit 1 Pretest B:

tomorrowBe sure all your density calculations are

done.Objectives 8 through 11 quiz tomorrow

Track Quiz and Exit Ticket

Did you get less than a 3 or 4 on Objectives 1 through 4? Come for extra help after school! Re-take a quiz on that objective

after school or next time we have a quiz.

Your goal is to earn a 3 or a 4 for EVERY objective!!

Carry out your procedure

Split up the work to be most efficient. Work carefully. Estimate the last digit on the

graduated cylinder. Neatly record your data in a table in

your notebook. Make sure your station looks as neat

when you are finished as it did when you started!

Equipment

250 mL beaker vinegar 100 mL graduated cylinder electronic balance water

Homework

Be sure all your density calculations are done.

Objectives 8-11 Quiz Thursday (study exit tickets!)

We’ll finish this lab tomorrow!

Objective: You will be able to: show what you know about

objectives 8-11. Do now:

Look at your tracking sheet Quiz grades for objectives 1-4. Write down the number of any objectives you have not yet earned a 3 or 4 on.

Agenda

I. Do nowII. Track Rounding (Obj. 11) exit ticket 2III. Objectives 8-11 Quiz!IV. Make up Objectives 1-4 QuizzesV. Work on lab graph, analysis and

conclusionHomework: Week 4 Homework p. 1: Mon.Lab graph, analysis and conclusion: due

Monday

Properties

Intensive: the property does NOT depend on the amount of stuff you have ex: temperature

Extensive: the property DOES depend on the amount of stuff you have ex: mass

Use your data to determine if density is an intensive property or an extensive property!

Track Rounding (Obj. 11)

You can erase/cross out your first exit ticket score if you earned a higher score!

When you finish your quiz…

Raise your hand and tell me if you need to retake any objective 1-4 quizzes.

Once you are done with quizzes, work on graphing your data, writing an analysis and conclusion Look at the lab handout for all the

details! Work on this silently until everyone

is done with their quizzes.

Need help on the lab?

Need extra help before you retake a quiz?

Work with me after school Monday!

Homework

Lab notebook: Monday Week 4 Homework p. 1: Mon.

Homework: Density of Pennies Procedure

Objective: You will be able to: determine the relationship between

mass and volume of pennies and compare density

Convert between scientific and regular notation.

Do now: Read through your procedure. Write down one question you have about it to share with your lab group.

Agenda

I. Do nowII. Carry out your procedure and collect data!III. Finish calculations and graph dataIV. Graph DataV. Scientific notation notes and practiceHomework: Week 4 Homework page 1: Mon.Pennies lab analysis and conclusion: MondayObjectives 8 through 11 quiz tomorrow

By 9:15…

1. Collect your data and organize it into the nicest table you have ever made

See the lab handout for more details.2. Graph both data sets on one set of

axes – this should be the nicest graph you have ever made

See the lab handout for more details. Complete the analysis and conclusion

in your lab notebook.

Scientific Notation

Homework

Pennies lab analysis and conclusion: Friday

Objectives 8 through 11 quiz tomorrow

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!

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!

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?

SWBAT convert between units in the SI system.

C: 22 September 2011

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