As You Come In

Get out your unit 1 goal sheet, fill it out and turn it in.

Grab Unit 2 notes booklet and the worksheet packet.

Review symbols cards with your shoulder partner

9/3 & 9/4 What:

You will determine the difference between accuracy & precision; convert using scientific notation & calculate % error

How: Review chemical symbols Take symbols quiz Notes WS #1 Chemical symbols Bingo! Homework: Complete WS #1 – worksheets are completion

points only!

Element Song

http://www.youtube.com/watch?v=GFIvXVMbII0

If they can learn the elements, why can’t you?

http://www.youtube.com/watch?v=GcTqTgBaMQM

http://www.youtube.com/watch?v=nUcy9eb8cYU

Unit 2Chapter 3Scientific

Measurement

Daily Challenge The number 602200000000000000000000 is used so frequently in chemistry that it has its own name; Avogadro’s number. What would be a better way of writing it?

Scientific Notation To write a number in

scientific notation:

1. Move the decimal so that the number is between 1 and 10.

2. The exponent is the number of tens places you moved the decimal

3. Moving the decimal right = - exponent Moving the decimal left = + exponent

Examples

65000 m = 0.0000156 s =

0.24 m/s = 6.7 mm =

6.5 x 104 m

1.56 x 10-5 s2.4 x 10-1 m/s

6.7 x 100 mm

To Write a number in Standard Form

Change it from scientific notation to a standard number by moving the decimal. The exponent becomes the number of spaces you moved the decimal.

Example1.4 x 106 = 1,400,0002.6 x 10-4 = 0.00026

Adding & Subtracting

1. Change the numbers to the same exponent.2. Add or subtract the numbers

Example: 4.1 x 106 + 8.5 x 107

0.41 x 107 + 8.5 x 107 = 8.91 x 107

Multiplication Multiply the numbers Add the exponents

Example: (4 x 106)(2 x 108) 8 x 1014

Division Divide the numbers Subtract the exponents

Example: (9 x 107)/(3 x 104) 3 x 103

Try It Out!

1. 3.5 x 104 + 5.1 x 105

2. (5.7 x 108)(3.5 x 106)3. (6.9 x 106)/(4.5 x 103)

Answers

1. 5.45 x 105

2. 1.995 x 1015

3. 1.53 x 103

Or… Use your scientific calculator. The EE button means x10^

Do the Try it Out problems again using your calculator and see if you get the correct answers!

Accuracy & Precision Accuracy – compare to the CORRECT value

Ex: You should have gotten 1 gram of each material in the separation of mixtures lab

Accuracy & Precision Precision – compare to the values of two or more REPEATED MEASUREMENTS

Ex: Multiple trials

Accurate, Precise, Both, Neither?

Accurate

Accurate, Precise, Both, Neither?

Precise

Accurate, Precise, Both, Neither?

Neither

Accurate, Precise, Both, Neither?

Precise

Accurate, Precise, Both, Neither?

Both

Accurate, Precise, Both, Neither?

Accurate

Percent Error

Percent Error = |experimental - actual| actual value

The absolute value is present so that percent error is always POSITIVE!

X 100

Example Working in the laboratory, a student finds

the density of a piece of pure aluminum to be 2.85 g/cm3.  The accepted value for the density of aluminum is 2.699 g/cm3.  What is the student's percent error?

Percent Error = |2.85 – 2.699| 2.699

5.59%

X 100 =

Try It Out A student takes an object with an accepted

mass of 200.00 grams and masses it on his own balance.  He records the mass of the object as 196.5 g.   What is his percent error?

Percent Error = |196.5 – 200.00| 200.00

1.75%

X 100 =

STOP! Complete Worksheet #1 by

next class Worksheets are…

A completion grade (i.e. You do not get a grade until it is 100% finished)

10 points on time -2.5 points each day it’s late

As You Come In

Get out WS #1 to be checked

Get out U2 notes booklet Questions from Worksheet?

Agenda for 9/5 & 9/6 What:

You will identify and round significant figures

How: Symbols review Symbols quiz #2 Scientific notation quiz Notes: Sig Figs and Measurement Worksheet #2

Homework: Complete WS #2

Units in Chemistry When you add or subtract two numbers, they must

have the same units. The answer then has those units as well. Example: 4 m + 12 m = 16 m When you multiply, you also multiply the units. Examples:

4 m x 5 m = 20 m2

2 g x 3 s = 6g·s When you divide, you also divide the units. Examples:

4 m / 2 s = 2 m/s 8 g / 2 mL = 4g/mL

Think about it!

What does the word “significant” mean?

Significant Figures

The numbers that are known, plus a digit that is estimated

RULES***All nonzero numbers are significant***

125, 689 has 6 significant figures (sig figs)156 has 3 sig figs

1. Zeros between nonzero numbers are significant.

40.7 mL has ______ sig figs

870,009 g has _____ sig figs

3

6

RULES2. Zeros in front of nonzero

numbers are not significant

0.00011 s has _____ sig figs

0.956 g/mL has _____ sig figs

2

3

RULES3. Zeros at the end of a

number and to the right of a decimal are significant

85.0000 kg has _____ sig figs

2.00000000 L has _____ sig figs

6

9

RULES4. Zeros at the end of a

number are NOT significant. If there is a decimal at the end, they ARE.

2000. m/s has _____ sig figs

2000 m/s has _____ sig figs

4

1

EASY RULE!Decimal

NoDecimal

Start at the first nonzero number on the left and count every number right

Start at the first nonzero number on the right and count every number left

Look at these numbers again

2000. m/s has _____ sig figs

2000 m/s has _____ sig figs

Unlimited Significant Figures

Counting – There are 23 students in the classroom Could also be expressed as 23.0 or

23.00000000000000 etc. Conversion Factors – 60 min = 1

hour Exact quantities do not affect the

process of rounding

Try It Out How many sig figs?1. 0.001252. 1.125980003. 3,0004. 0.01001035. 5,500.6. 1.23 x 105

39

1

6

43

Rounding Round the following numbers so

that they have 3 significant figures:1. 1.36579 =2. 120 =3. 145,256,987 =4. 0.0001489651 =

1.37

1.20 x 102 OR 120.145,000,000

0.000149

Stop Here!

You have 10 minutes to work on the front side of WS #2

To Multiply & Divide Sig Figs…

1. Count the number of sig figs in each number

2. Round the answer so that it has the same number of sig figs as the number in the problem with the fewest.

Example 1 16.19 g / 4.2 mL

= 3.8547619 g/mL 16.19 has 4 sig figs 4.2 has 2 sig figs, so the answer

should have 2 sig figs

3.9 g/mL

Example 2 9.3 m x 0.00167 m = 0.015531m2

9.3 m has 2 sig figs, 0.00167 has 3 sig figs

Therefore, the answer must have only 2 sig figs.

0.016 m2

Try It Out!

(1.23)(0.011) =12.63000/100 = (1.23 x 106)(3.5 x 104) =0.0045912/6.570 =

0.0140.1

4.3 x 1010

6.988 x 10-4

Stop

Complete Worksheet #2

Bluff1A. How many sig figs are in 0.001023?1B. Solve 456 x 3.22A. How many sig figs would the answer have if you calculated 2.1 x 0.01? 2B. How many sig figs are in 123,000?3A. Solve 2.7 x 33B. How many sig figs would the answer have if you calculated 1.4/3.789?

Bluff4A. What is 235,489 rounded to 2 sig figs?4B. Solve 1/2365A. Solve 3.7914/9.25B. What is 1,926,560 rounded to 1 sig fig?6A. How could you write 230 with 3 sig figs?6B. What is 0.00056798 rounded to 4 sig figs?

As You Come In

Get out WS #2 and have checked for points

Agenda 9/9

What: You will apply using sig figs in

measurement to a practical lab How:

Sig Figs Race Sig Figs Quiz Notes- sig figs in measurement Practical Lab

Homework: Complete pages 10 & 11 in notes from your book

Sig Figs in Measurements

When doing any measurements in chemistry, it is important that you use the correct precision.

All measurements should be made by writing all units you know and estimating the last unit.

Examples

20 40 60

20 40 60

54

38

4 8 102 6 12 14

13.9

503010

10 30 50 70

70

More Examples!

2 4 6

0.5 1 1.5

20 40 60

3.4

1.16

72

Units of Measurement

Every measurement in chemistry MUST HAVE A UNIT!

Without a unit, the number means nothing!

We will use SI units in class

Wrap Up – Clicker!

2 4 6

0.5 1 1.5

20 40 60

5.3

1.58

43

5

As You Come In

Get out your Unit 2 notes, calculator and pencil.

Music today will play during review time

Agenda 9/10 & 9/11

What: You will calculate conversion problems.

How: Mix/Group Review Conversions Notes Work on WS #3

Homework: Try some of the problems on WS #3

Review Time

Open up your notebooklet to p. 11. Answer questions 1 – 6.

Get up and move around the classroom. When the instructor says “group by the answer to #___” you have to form a group of students that is the same as the answer to the problem!

Mix/Group How many sig figs:

1. 102.325002. 560.3. 0.0012501

What is the exponent?:4. 420= 5. 36,000,0006. 60 =

Review Time

Now answer questions 7 – 11 on your own.

When you are finished, pair up with your face partner and share your answers.

Think-Pair-Share

Round these numbers so that they have 3 sig figs:

7. 103,2508. 567.99. 0.001256110. 10011. Read the measurement below

correctly.

103,000 or 1.03 x 105

568 or 5.68 x 102

0.00126 or 1.26 x 10-3

100. or 1.00 x 102

20 40 60 43

Challenge

Would you be breaking the speed limit in a 40 mi/h zone if you were traveling at 60 km/h?

http://www.youtube.com/watch?v=Qhm7-LEBznk

Challenge

How tall are you in Cheetos?

Cheetos conversion

Conversion Factors

Definition: a ratio of equivalent units

It is always equal to 1 When multiplying by a conversion

factor, the numerical value is changed, but the actual size of the quantity remains the same

Conversion Factors When working with conversion

factors, we use the Factor-Label Method (dimensional analysis)

The factor is the number that explains the relationship between two things

The labels are its’ units

Examples

4 quarters = 1 1 dollar

OR 1 dollar = 1

4 quartersFactor

Label

Examples

12 months = 1

1 year 1 foot = 1

12 inches

Rules for using Conversion Factors

1. Always start by writing what you know from the problem.

2. Multiply by a conversion factor so that the units cancel out (same unit in numerator and denominator)

3. Continue converting until your answer is in the desired units.

Example 1 – your age in minutes

Checklist:

I started by writing what I knew

All units cancel

My answer is in minutes

Example 2 How many dollars do you have if

you have 38 quarters?

9.5 dollars

Example 3 How many nanoseconds are in one week?

600,000,000,000,000 nanoseconds

Example 4 How many milligrams are in 12 g?

12,000 mg

TRY IT OUT! Now try the next three problems in your notes on your own.

Checklist:

I started by writing what I knew

All units cancel

My answer is in desired units

The Answers…

1. 790,000,000 seconds

2. 6.71 x 103 grams3. 5.3 x 103 mL

Still don’t get it?

Watch this factor-label method video!

STOP! Start Worksheet #3. You must show work and you

must use the factor-label method!

Remember worksheets are completion grades- no credit until done completely!

As You Come In

Get out WS #3 and notes Calculate the following problem on

the back of your notes: On my last birthday Mrs. Hammond

turned 1.23 x 109 seconds old. How many years old am I?

Agenda 9/12 & 9/13 What:

You will calculate density problems. How:

Pass the problem review Notes-Density WS #4 Begin Density Lab

Homework: Complete WS 4

Review

Pass the Problem Each student has a problem to solve.

The first student will do step 1 (write what you know) and pass the paper to the next student who will complete the second step. Continue passing the paper until you get the answer.

Example: How many days are in 60 seconds?

Conversion Problem Answers

56996,40081,000,000

Density Review

Density = Mass/VolumeVolume of liquids is measured in liters or milliliters

Volume of solids is length x width x height

Example A bar of silver has a mass of

68.0 g and a volume of 6.48 cm3. What is the density of silver?

10.5 g/cm3

Example A copper penny has a mass of 3.1

g and the density of copper is 8.8571 g/cm3. What is the volume of the penny?

0.35 cm3

Try It Out What is the mass of a pure silver

coin that has a volume of 1.3 cm3? The density of silver is 10.5 g/cm3.

14 g

Using Density as a Conversions Factor

What volume of ethanol (in liters) would you have if you acquire 126.56g of ethanol? The density of ethanol is 0.789 g/cm3.

0.16032 L

Try It Out in your notes!

The density of apples is 0.641 g/cm3. If an apple has a mas of 0.089 kg, what is its volume?

140 cm3

STOP!You have 10 min. to work on WS #4

As You Come In

Get out WS #4 to be checked Complete the Wrap Up on

Density on page 15 of your notes.

Then list the letters in order of how they would layer out if this were put into a graduated cylinder.

Density Review

Density = Mass/VolumeA – 1.23 g/mL

C – 1.28 g/mL

D – 1.71 g/mL

B – 2.1 g/mL

Agenda 9/16

What: You will apply correct measurement

techniques and calculate density. How:

Conversions & Density Quiz Measurement & Density Lab

Homework: Missing Assignments

Wrap Up

What questions do you have on the lab?

As You Come In

Get out your Measurement & Density Lab, a pencil and your calculator and your U2 notes

Pick up the U2 Test Review

Agenda 9/17 & 9/18 What:

You will solve density & conversion problems

How: Which word am I? Review Complete Measurement & Density Lab

Homework: U3 Test Review *U3 Test next block *All missing assignments for when

you take your test!

Review – Which Word Am I (p. 15 Notes)

1. Mass divided by volume2. The numbers that are known in a measurement

plus one estimated digit3. How close your measurements are to the true

value4. How close your measurements are to each other5. Convert 3.69 meters into inches.6. What is the volume of a cube that has a mass of

7.9 g and a density of 9.45 g/cm3?

Answers

1. Density 2. Significant Figures 3. Accuracy 4. Precision 5. 145 inches 6. .84 cm3

As You Come In

Get out your Unit 2 Test Review to be checked

Turn in your Measurement Lab if you haven’t yet!

Agenda 9/19 & 9/20

WHAT: You will be assessed on Unit 2 material

How: WS Race Take Unit 2 Test

Homework: PT Basics Activity (Poster)

After the Test

PT BASICS HELP