1. Chapter 3 Scientific Measurement
Unit 2
Chapter 3
Scientific Measurement

2. Today… Turn in: Nothing Our Plan: Daily Challenge
Scientific Notation, Accuracy, Precision, Error Notes
Worksheet #1
Wrap Up – Rally Robin
Homework (Write in Planner):
Complete WS #1 by next class

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

4. Scientific Notation To write a number in scientific notation:
Move the decimal so that the number is between 1 and 10.
The exponent is the number of tens places you moved the decimal
Moving the decimal right = - exponent
Moving the decimal left = + exponent

5. Examples 65000 m = 0.0000156 s = 0.24 m/s = 6.7 mm = 6.5 x 104 m
1.56 x 10-5 s
2.4 x 10-1 m/s
6.7 x 100 mm

6. To Write a number in Standard Form
Change it from scientific notation to a standard number by moving the decimal.
Example
1.4 x 106 = 1,400,000
2.6 x 10-4 =

7. Adding & Subtracting Change the numbers to the same exponent.
Add or subtract the numbers
Example: 4.1 x x 107
0.41 x x 107 = 8.91 x 107

8. Multiplication Multiply the numbers Add the exponents
Example: (4 x 106)(2 x 108)
8 x 1014

9. Division Divide the numbers Subtract the exponents
Example: (9 x 107)/(3 x 104)
3 x 103

10. Try It Out!
3.5 x x 105
(5.7 x 108)(3.5 x 106)
(6.9 x 106)/(4.5 x 103)

11. Answers
5.45 x 105
1.995 x 1015
1.53 x 103

12. 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!

13. Accuracy & Precision Accuracy – compare to the CORRECT value
Precision – compare to the values of two or more REPEATED MEASUREMENTS

14. Accurate, Precise, Both, Neither?

15. Accurate, Precise, Both, Neither?

16. Accurate, Precise, Both, Neither?

17. Accurate, Precise, Both, Neither?

18. Accurate, Precise, Both, Neither?

19. Accurate, Precise, Both, Neither?

20. Percent Error Percent Error = |experimental - actual| actual value
The absolute value is present so that percent error is always POSITIVE!
X 100

21. Example 5.59% Percent Error = |2.85 – 2.699| 2.699 X 100 =
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 g/cm3.  What is the student's percent error?
Percent Error = |2.85 – 2.699|
2.699
5.59%
X 100 =

22. Try It Out 1.75% Percent Error = |196.5 – 200.00| 200.00 X 100 =
A student takes an object with an accepted mass of grams and masses it on his own balance.  He records the mass of the object as g.   What is his percent error?
Percent Error = |196.5 – |
200.00
1.75%
X 100 =

23. 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

24. Wrap Up
Rally Robin
Pair up with your shoulder partner. Divide a deck of cards in half. Take turns asking each other the questions on the cards.
Be sure to cover the answer with your finger.

25. Today… Turn in: Get out WS#1 to Check Our Plan:
Scientific Notation Clicker Review
Scientific Notation Quiz
Notes – Significant Figures/Units of Measurement
WS #2
Bluff
Homework (Write in Planner):
Complete WS #2 by next class (9/12)
QUIZ OVER SIG FIGS NEXT TIME!

26. 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.
4 m / 2 s = 2 m/s
8 g / 2 mL = 4g/mL

27. What does the word “significant” mean?
Challenge!
What does the word “significant” mean?

28. Significant Figures
The numbers that are known, plus a digit that is estimated

29. RULES 3 6 Zeros between nonzero numbers are significant.
***All nonzero numbers are significant***
125, 689 has 6 significant figures (sig figs)
156 has 3 sig figs
Zeros between nonzero numbers are significant.
40.7 mL has ______ sig figs
870,009 g has _____ sig figs 3 6

30. RULES Zeros in front of nonzero numbers are not significant 2 3
s has _____ sig figs
0.956 g/mL has _____ sig figs 2 3

31. RULES
Zeros at the end of a number and to the right of a decimal are significant
kg has _____ sig figs
L has _____ sig figs 6 9

32. RULES
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

33. Memorize!
EASY RULE!
Decimal No
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

34. Unlimited Significant Figures
Counting – There are 23 students in the classroom
Could also be expressed as 23.0 or etc.
Conversion Factors – 60 min = 1 hour
Exact quantities do not affect the process of rounding

35. Try It Out How many sig figs? 0.00125 1.12598000 3 3,000 0.0100103 9
5,500.
1.23 x 105 3 9 1 6 4 3

36. Rounding
Round the following numbers so that they have 3 significant figures: =
120 =
145,256,987 = =
1.37
1.20 x 102 OR 120.
145,000,000

37. To Multiply & Divide Sig Figs…
Count the number of sig figs in each number
Round the answer so that it has the same number of sig figs as the number in the problem with the fewest.

38. Example 1 16.19 g / 4.2 mL = 3.8547619 g/mL 3.9 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

39. Example 2
9.3 m x m
= m2
9.3 m has 2 sig figs, has 3 sig figs
Therefore, the answer must have only 2 sig figs.
0.016 m2

40. Try It Out!
(1.23)(0.011) =
/100 =
(1.23 x 106)(3.5 x 104) =
/6.570 =
0.014
0.1
4.3 x 1010
6.988 x 10-4

41. Stop
Complete Worksheet #2

42. Bluff
1A. How many sig figs are in ? 1B. Solve 456 x 3.2 2A. 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 3 3B. How many sig figs would the answer have if you calculated 1.4/3.789?

43. Bluff
4A. What is 235,489 rounded to 2 sig figs? 4B. Solve 1/236 5A. Solve /9.2 5B. What is 1,926,560 rounded to 1 sig fig? 6A. How could you write 230 with 3 sig figs? 6B. What is rounded to 4 sig figs?

44. Today… Turn in: Get out WS#2 to Check Our Plan: Sig Fig Race
Sig Fig Quiz
Notes – Significant Figures in Measurement
Practical Lab - Measurement
Wrap Up – Measure Up
Homework (Write in Planner):
Fill out p. 9 – top of 11 using your text by next class!

45. 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.

46. Examples 54 70 10 30 50 20 40 60 38 10 30 50 70 20 40 60
13.9 2 4 6 8 10 12 14

47. More Examples!
3.4 2 4 6
1.16
0.5 1
1.5 72 20 40 60

48. 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

49. Wrap Up – Clicker!
5.3 2 4 5 6
1.58
0.5 1
1.5 43 20 40 60

50. Today Before Class: Get out Note Booklet, Calculator, & Pencil
Our Plan:
Mix/Group Review (#1-11)
Challenge
Notes - Conversions
WS #3
Wrap Up – Practice Problem from the Worksheet
Homework (Write in Planner):
Try out some of the problems on the worksheet

51. 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!

52. Review Time Now answer questions 7 – 11 on your own.
When you are finished pair up with your face partner and share your answers.

53. Mix/Group How many sig figs: 102.32500 560. 0.0012501
What is the exponent?:
420=
36,000,000
60 =

54. Think-Pair-Share
Round these numbers so that they have 3 sig figs:
103,250
567.9
100
Read the measurement below correctly.
103,000 or 1.03 x 105
568 or 5.68 x 102
or 1.26 x 10-3
100. or 1.00 x 102 43 20 40 60

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

57. Challenge
How old are you, in minutes?

58. 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

59. 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

60. Examples 1 dollar = 1 4 quarters = 1 OR 4 quarters 1 dollar Factor
Label

61. Examples
12 months = 1
1 year
1 foot = 1
12 inches

62. Rules for using Conversion Factors
Always start by writing what you know from the problem.
Multiply by a conversion factor so that the units cancel out (same unit in numerator and denominator)
Continue converting until your answer is in the desired units.

63. Example 1 – your age in minutes
Checklist:
I started by writing what I knew
All units cancel
My answer is in minutes

64. Example 1 – your age in minutes
16 years x
365 days
1 year x
24 hours
1 day x
60 minutes
1 hour =
8,409,600 minutes
Checklist:
I started by writing what I knew
All units cancel
My answer is in minutes

65. Mrs. C’s top 4 reasons for NOT using the Factor-Label Method
You’re super-intelligent and enjoy solving relatively simple problems in the most complex manner.
You're tired of always getting the correct answers.

66. Mrs. C’s top 4 reasons for NOT using the Factor-Label Method
You’re artistic, and rather than using Mrs. C’s concrete-sequential method of solving problems you want to use your own random method such that you create abstract patterns and designs on paper that you might be able to sell as artwork.

67. Mrs. C’s top 4 reasons for NOT using the Factor-Label Method
Let's say that you have no interest in going to the prom or making the soccer team, and you don't mind being unpopular, unattractive, ignorant, insecure, uninformed, and unpleasant.
Otherwise,
You Need the Factor-Label Method!

68. Testimonials
"I was a South High School student who dozed off while Mrs. C taught us the Factor-Label method in chemistry. I never quite got the hang of it. It irritated me... all of those fractions. I never really liked fractions. Although my grades had been pretty high, I got a D in chemistry and subsequently did not take any more high school science classes. It was not long before I started on drugs, and then used crime to support my drug habit. I have recently learned the factor-label method and realize how simply it could have solved all of my problems. Alas, it is too late. I won't get out of prison until 2022 and even then, my self image is permanently damaged. I attribute all of my problems to my unwillingness to learn the factor-label method." -Jane

69. Testimonials
"I thought I knew everything and that sports was the only thing that mattered in high school. When Mrs. C taught our class the factor-label method, I didn't care about it at all. I was making plans for the weekend with my girlfriend who loved me because I was a running back and not because of chemistry. While other kids were home solving conversion problems, I was practicing making end sweeps. Then one day I was hit hard. Splat. My knee was gone. I was a total loser. My girl friend deserted me. My parents, who used to brag about my football stats, stopped loving me and started getting on my case about grades. I decided to throw myself into my school work. But I couldn't understand anything. I would get wrong answers all of the time. I now realize that my failure in school came from never having learned the factor-label method. I thought everyone else was smarter than me. After the constant humiliation of failing I finally gave up. I am worthless. I have no friends, no skills, no interests. I have now learned the factor-label method, but it is too late." -Bill

70. Example 2 How many dollars do you have if you have 38 quarters?

71. Example 3
How many nanoseconds are in one week?
600,000,000,000,000 nanoseconds

72. Example 4
How many milligrams are in 12 g?
12,000 mg

73. 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

74. The Answers…
790,000,000 seconds
6.71 x 103 grams
5.3 x 103 mL

75. STOP!
Start Worksheet #3.
You must show work and you must use the factor-label method!

76. Today… Turn in: Get WS #3 out
On Mrs. C’s birthday she will be x 109 seconds old. How many years old will she be?
Our Plan:
Pass the Paper
Work on Worksheet #3
Notes - Density
WS #4
Wrap Up – Density Problem
Homework (Write in Planner):
Complete WS #3 &#4 by next class
QUIZ OVER BOTH WORKSHEETS NEXT TIME!

77. 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?

78. Pass the Paper Answers
569
96,400 8
1,000,000

79. Density Review Density = Mass/Volume
Volume of liquids is measured in liters or milliliters
Volume of solids is length x width x height

80. Do formulas confuse you?
Try this visual approach…

81. 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

82. Example
A copper penny has a mass of 3.1 g and the density of copper is g/cm3. What is the volume of the penny?
0.35 cm3

83. 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

84. STOP!
Complete Worksheet #4

85. Wrap Up - Density Review (p. 15 Notes)
Four graduated cylinders each contain a different liquid: A, B, C, and D.
Liquid A: mass = 18.5 g; volume = 15.0 mL
Liquid B: mass = 16.5 g; volume = 8.0 mL
Liquid C: mass = 12.8 g; volume = 10.0 mL
Liquid D: mass = 20.5 g; volume = 12.0 mL
Examine the information given for each liquid, calculate the density, and predict the layering of the liquids if they were carefully poured into a larger graduated cylinder.

86. Density Review Density = Mass/Volume A – 1.23 g/mL C – 1.28 g/mL
D – 1.71 g/mL
B – 2.1 g/mL

87. Today… Turn in: Get WS #3 & #4 out to be graded Our Plan:
Which Word Am I?
Conversions/Density Quiz
Lab
Wrap Up – High Five
Homework (Write in Planner):
Missing Work

88. Review – Which Word Am I (p. 15 Notes)
Mass divided by volume
The numbers that are known in a measurement plus one estimated digit
How close your measurements are to the true value
How close your measurements are to each other
Convert 3.69 meters into inches.
What is the volume of a cube that has a mass of 7.9 g and a density of 9.45 g/cm3?

89. Wrap Up
What questions do you have on the lab?

90. Today… Turn in: Get Lab Packet Out, Calculator, Pencil Our Plan:
LAB – DUE TODAY
Work Day
Missing Work
Test Review
Homework (Write in Planner):
Test Review due next class
TEST NEXT TIME!

91. Today… Turn in: Get out Test Review to check
Turn in Measurement Lab if you haven’t yet!
Our Plan:
Worksheet Race
Go over Test Review, then turn it in
Unit 3 Test
Periodic Table Basics Activity
Homework (Write in Planner):
PT BASICS DUE NEXT MONDAY!

92. After the Test
PT BASICS HELP