1. Chapter 1: Scientists’ Tools

2. Chemistry is an Experimental Science This chapter will introduce the following tools that scientists use to “do chemistry”  Section 1.1: Observations & Measurements  Section 1.2: Converting Units  Section 1.3: Significant Digits  Section 1.4: Scientific Notation

3. Section 1.1—Observations & Measurements

4. Collecting Data by Making Observations

5. Qualitative Data: Common Mistake: Clear vs Colorless Clear See-through Cloudy Parts are see- through with solid “cloud” in it Opaque Cannot be seen through at all Colorless does not describe transparency Words to describe transparency  You can be clear & colored  You can be cloudy & colored

6. Clear versus Colorless Cherry Kool-ade Example: Describe the following in terms of transparency words & colors Whole Milk Water

7. Clear versus Colorless Cherry Kool-adeClear & red Example: Describe using the terms of transparency & color Whole Milk Water Opaque & white Clear & Colorless

8. Types of Quantitative Data Quantity Mass (how much stuff is there) Common Unit gram (g) Instrument used Balance Volume (how much space it takes up) milliLiters (mL) Graduated cylinder Temperature (how fast the particles are moving) Celsius (°C) Thermometer Length Meters (m) Meter stick Time Seconds (sec) stopwatch Energy Joules (J) (Measured indirectly calorimeter)

9. Measuring Volume Each instrument has different calibrations. Beaker A: 10 ml calibrations Volume = 28 mL Graduated Cylinder B: 1 ml calibrations Volume = 28.3 mL Buret C: 0.1 calibrations Volume = 28.32 mL The more lines, the more precise the instrument. Always record the numbers you definitely can read off the instrument, plus an estimated digit.

10. Use the bottom of the meniscus to record the volume of the liquid. 36.5 ml

11. Uncertainty in Measurement Every measurement has a degree of uncertainty The last decimal you write down is an estimate  Write down a “5” if it’s in-between lines  Write down a “0” if it’s on the line 5 mL 10 15 20 25 mL 5 mL 10 15 20 25 mL Remember: Always read liquid levels from the bottom of the meniscus Example: Read the measurements

12. Uncertainty in Measurement Every measurement has a degree of uncertainty The last decimal you write down is an estimate  Write down a “5” if it’s in-between lines  Write down a “0” if it’s on the line 5 mL 10 15 20 25 mL 5 mL 10 15 20 25 mL Example: Read the measurements It’s in- between the 10 & 11 line 10.5 mL It’s on the 12 line 12.0 mL

13. Measuring Length

14. Measurement Tool for Length 1.5 cm 1.95 cm

15. Uncertainty in Measurement Example: Read the measurements 1234567812345678

16. Uncertainty in Measurement Example: Read the measurements 1234567812345678 It’s right on the 6.9 line 6.90 It’s between the 3.8 & 3.9 line 3.85

17. Measurement Tool for Temperature What is the measurement of thermometer B seen to the right?

18. Measurement Tool for Mass Always read exactly what the balance says Do not add any additional numbers!

19. HINT:Uncertainty in Measurement Choose the right instrument  If you need to measure out 5 mL, don’t choose the graduated cylinder that can hold 100 mL. Use the 10 or 25 mL cylinder The smaller the measurement, the more an error matters—use extra caution with small quantities  If you’re measuring 5 mL & you’re off by 1 mL, that’s a 20% error  If you’re measuring 100 mL & you’re off by 1 mL, that’s only a 1% error

20. Section 1.2—Accuracy, Precision & Significant Digits

21. Gathering Data Multiple trials help ensure that you’re results weren’t a one-time fluke! Precise—getting consistent data (close to one another) Accurate—getting the “correct” or “accepted” answer consistently Example: Describe each group’s data as not precise, precise or accurate Correct value

22. Precise & Accurate Data Example: Describe each group’s data as not precise, precise or accurate Correct value Precise, but not accurate Precise & Accurate Not precise

23. Can you be accurate without precise? Correct value This group had one value that was almost right on…but can we say they were accurate? No…they weren’t consistently correct. It was by random chance that they had a result close to the correct answer.

24. Can you be accurate without precise? Correct value This group had one value that was almost right on…but can we say they were accurate?

25. You Try! Accepted Value = bulls-eye *not accurate but precise *accurate & precise *not precise nor accurate

26. Example: Below is a data table produced by three groups of students who were measuring the mass of a paper clip which had a known mass of 1.0004g. Group 1Group 2Group 3Group 4 1.01 g2.863287 g10.13251 g2.05 g 1.03 g2.754158 g10.13258 g0.23 g 0.99 g2.186357 g10.13255 g0.75 g Average1.01 g2.601267 g10.13255 g1.01 g Group 1 has the most precise (all 3 measurements are consistent with each other) & accurate (the average value of the 3 trials are closest to the accepted value of 1.0004g) data.

27. Percent Error A calculation designed to determine accuracy % Error = |Accepted - Experimental| x 100 |Accepted|

28. You Try! A student measured an unknown metal to be 1.50 grams. The accepted value is 1.87 grams. What is the percent error? % Error = |1.87 –1.50| x 100 1.87 = 20% error

29. Significant Digits A significant digit is anything that you measured in the lab—it has physical meaning The real purpose of “significant digits” is to know how many places to record in an answer from a calculation But before we can do this, we need to learn how to count significant digits in a measurement

30. Taking & Using Measurements You learned in Section 1.2 how to take careful measurements Most of the time, you will need to complete calculations with those measurements to understand your results 1.00 g 3.0 mL = 0.3333333333333333333 g/mL If the actual measurements were only taken to 2 or 3 decimal places… how can the answer be known to and infinite number of decimal places? It can’t!

31. Significant Digit Rules 1 All measured numbers are significant 2 All non-zero numbers are significant 3 Middle zeros are always significant 4 Trailing zeros are significant if there’s a decimal place 5 Leading zeros are never significant

32. All the fuss about zeros 102.5 g Middle zeros are important…we know that’s a zero (as opposed to being 112.5)…it was measured to be a zero 125.0 mL The convention is that if there are ending zeros with a decimal place, the zeros were measured and it’s indicating how precise the measurement was. 125.0 is between 124.9 and 125.1 125 is between 124 and 126 0.0127 m The leading zeros will dissapear if the units are changed without affecting the physical meaning or precision…therefore they are not significant 0.0127 m is the same as 127 mm

33. Sum it up into 2 Rules: Oversimplification Rule 1 If there is no decimal point in the number, count from the first non-zero number to the last non-zero number 2 If there is a decimal point (anywhere in the number), count from the first non-zero number to the very end The 4 earlier rules can be summed up into 2 general rules

34. Examples of Summary Rule 1 Example: Count the number of significant figures in each number 124 20570 200 150 1 If there is no decimal point in the number, count from the first non-zero number to the last non-zero number

35. Examples of Summary Rule 1 Example: Count the number of significant figures in each number 124 20570 200 150 1 If there is no decimal point in the number, count from the first non-zero number to the last non-zero number 3 significant digits 4 significant digits 1 significant digit 2 significant digits

36. Examples of Summary Rule 2 Example: Count the number of significant figures in each number 0.00240 240. 370.0 0.02020 2 If there is a decimal point (anywhere in the number), count from the first non-zero number to the very end

37. Examples of Summary Rule 2 Example: Count the number of significant figures in each number 0.00240 240. 370.0 0.02020 3 significant digits 4 significant digits 2 If there is a decimal point (anywhere in the number), count from the first non-zero number to the very end

38. Importance of Trailing Zeros Just because the zero isn’t “significant” doesn’t mean it’s not important and you don’t have to write it! “250 m” is not the same thing as “25 m” just because the zero isn’t significant The zero not being significant just tells us that it’s a broader range…the real value of “250 m” is between 240 m & 260 m. “250. m” with the zero being significant tells us the range is from 249 m to 251 m

39. Let’s Practice Example: Count the number of significant figures in each number 1020 m 0.00205 g 100.0 m 10240 mL 10.320 g

40. Let’s Practice Example: Count the number of significant figures in each number 1020 m 0.00205 g 100.0 m 10240 mL 10.320 g 3 significant digits 4 significant digits 5 significant digits

41. Rounding Example: Round each number to number of sig figs in the parentheses 1320 m (2) 0.00205 g (2) 752.4 m (3) 7.007 mL (3) 10.350 g (3) 1.Go to the digit you want to round to 2.Look to the right. If the number is less than 5, the digit you want to round to stays the same. Drop the rest of the digits If the number is greater than 5, the digit you want to round to moves up by one. Drop the rest of the digits.

42. Rounding Example: Round each number to number of sig figs in the parentheses 1320 m 0.00205 g 752.4 m 7.007 mL 10.350 g 1300.0021 752 7.01 10.4 1.Go to the digit you want to round to 2.Look to the right. If the number is less than 5, the digit you want to round to stays the same. Drop the rest of the digits If the number is greater than 5, the digit you want to round to moves up by one. Drop the rest of the digits.

43. Performing Calculations with Sig Figs 1 Addition & Subtraction: Answer has least number of decimal places as appears in the problem 2 Multiplication & Division: Answer has least number of significant figures as appears in the problem When recording a calculated answer, you can only be as precise as your least precise measurement Always complete the calculations first, and then round at the end!

44. EXCEPTION: When adding/subtracting and then multiplying/dividing, follow the rules for addition/subtraction first and then apply that number of sig figs to the multiplication/division rules. (6.350- 6.010) / 2.0 = _______.340 / 2.0 = 3 s.f. / 2 s.f. =.17

45. Addition & Subtraction Example #1 Example: Compute & write the answer with the correct number of sig digs 15.502 g + 1.25 g This answer assumes the missing digit in the problem is a zero…but we really don’t have any idea what it is 1 Addition & Subtraction: Answer has least number of decimal places as appears in the problem 16.752 g

46. Addition & Subtraction Example #1 Example: Compute & write the answer with the correct number of sig digs 15.502 g + 1.25 g 1 Addition & Subtraction: Answer has least number of decimal places as appears in the problem 16.752 g 16.75 g 3 decimal places 2 decimal places Lowest is “2” Answer is rounded to 2 decimal places

47. Addition & Subtraction Example #2 Example: Compute & write the answer with the correct number of sig digs 10.25 mL - 2.242 mL This answer assumes the missing digit in the problem is a zero…but we really don’t have any idea what it is 1 Addition & Subtraction: Answer has least number of decimal places as appears in the problem 8.008 mL

48. Addition & Subtraction Example #2 Example: Compute & write the answer with the correct number of sig digs 10.25 mL - 2.242 mL 1 Addition & Subtraction: Answer has least number of decimal places as appears in the problem 8.01 mL 2 decimal places 3 decimal places Lowest is “2” Answer is rounded to 2 decimal places 8.008 mL

49. Multiplication & Division Example #1 Example: Compute & write the answer with the correct number of sig digs 10.25 g 2.7 mL = 3.796296296 g/mL 2 Multiplication & Division: Answer has least number of significant figures as appears in the problem

50. Multiplication & Division Example #1 Example: Compute & write the answer with the correct number of sig digs 3.8 g/mL 4 significant digits 2 significant digits Lowest is “2” Answer is rounded to 2 sig digs 10.25 g 2.7 mL = 3.796296296 g/mL 2 Multiplication & Division: Answer has least number of significant figures as appears in the problem

51. Multiplication & Division Example #2 Example: Compute & write the answer with the correct number of sig digs 1.704 g/mL  2.75 mL 4.686 g 2 Multiplication & Division: Answer has least number of significant figures as appears in the problem

52. Multiplication & Division Example #2 Example: Compute & write the answer with the correct number of sig digs 4.69 g 4 significant dig 3 significant dig Lowest is “3” Answer is rounded to 3 significant digits 2 Multiplication & Division: Answer has least number of significant figures as appears in the problem 1.704 g/mL  2.75 mL 4.686 g

53. Let’s Practice #1 Example: Compute & write the answer with the correct number of sig digs 0.045 g + 1.2 g

54. Let’s Practice #1 Example: Compute & write the answer with the correct number of sig digs 1.2 g 3 decimal places 1 decimal place Lowest is “1” Answer is rounded to 1 decimal place 1.245 g Addition & Subtraction use number of decimal places! 0.045 g + 1.2 g

55. Let’s Practice #2 Example: Compute & write the answer with the correct number of sig digs 2.5 g/mL  23.5 mL

56. Let’s Practice #2 Example: Compute & write the answer with the correct number of sig digs 59 g 2 significant dig 3 significant dig Lowest is “2” Answer is rounded to 2 significant digits 2.5 g/mL  23.5 mL 58.75 g Multiplication & Division use number of significant digits!

57. Let’s Practice #3 Example: Compute & write the answer with the correct number of sig digs 1.000 g 2.34 mL

58. Let’s Practice #3 Example: Compute & write the answer with the correct number of sig digs 0.427 g/mL 4 significant digits 3 significant digits Lowest is “3” Answer is rounded to 3 sig digs 1.000 g 2.34 mL = 0.42735 g/mL Multiplication & Division use number of significant digits!

59. Let’s Practice #4 Example: Compute & write the answer with the correct number of sig digs 1.704 m  2.75 m

60. Let’s Practice #4 Example: Compute & write the answer with the correct number of sig digs 4.69 m 2 4 significant dig 3 significant dig Lowest is “3” Answer is rounded to 3 significant digits 1.704 m  2.75 m 4.686 g Multiplication & Division use number of significant digits!

61. Multi Step Calculations

62. Section 1.3—Metric System & Dimensional Analysis

63. The Metric System Universal system of measurements Based on the powers of ten Only the US and Myanmar do not use this system

64. Metric Prefixes  Used in the metric system to describe smaller or larger amounts of base units The Great Magistrate King Henry Died by drinking chocolate milk Monday near paris T G M K H D b d c m μ n p 1 x 10 12 1 x 10 9 1 x 10 6 1000 100 10 1.1.01.001 1 x 10 -6 1 x 10 -9 1 x 10 -12 Base Units have a value of 1 Examples are: Liters (L) meters (m) grams (g) seconds (s) Place a prefix in front of a base unit to make a larger or smaller numberExample: ks = kilosecond mm = millimeter cg = centigram m = meter

65. Converting with the Metric System Using the Ladder Method 1.Determine the starting point. 2.Count the jumps to your endpoint. 3.Move the decimal the same number of jumps in the same direction 4.If using the other prefixes, remember that there is a difference of 1000 or 3 places between each. T G M K H D b d c m μ n p EXAMPLE: 4 km = ______ m 4000

66. Examples T G M K H D b d c m μ n p Convert 15 cl into ml Convert 6000 mm into Km Convert 1.6 Dag into dg Convert 3.4 nm into m 150 ml.006 Km 160 dg.0000000034 m

67. A Different Way to Convert between Units Dimensional Analysis is another method It uses equivalents called conversion factors to make the exchange

68. Conversion Factors Change the Equivalents to Conversion Factors 1 foot = 12 inches or 4 quarters = 1 dollar What happens if you put one on top of the other? You create a ratio equal to 1 1 foot 12 inches 4 quarters 1 dollar

69. Common Equivalents 1 ft 12 in 1 in 2.54 cm 1 min 60 s 1 hr 3600 s 1 quart (qt) 0.946 L 4 pints 1 quart 1 pound (lb) 454 g = = = = = = =

70. Steps for using Dimensional Analysis 1 Write down your given information 2 Determine what you want. 3 Use or create a conversion factor to compare what you have to what you want 4 Set up the math so that the given unit is on the bottom of the conversion factor… Calculate the answer. Multiply across the top. Multiply across the bottom of the expression. Divide the bottom by the top 5

71. Example #1 Example: How many yards are in 52 feet? 52 ft 1 Write down your given information

72. Example #1 Example: How many yards are in 52 feet? 52 ft 2 Determine what you want. = ________ yds

73. Example #1 Example: How many yards are in 52 feet? 52 ft = ________ yds 3 &4 Use or create a conversion factor to compare what you have to what you want The equivalent with these 2 units is: 3 ft = 1 yd A tip is to arrange the units first and then fill in numbers later!  ft yd Put the unit on bottom that you want to cancel out! 3 1

74. Example #1 Example: How many yards are in 52 feet? 52 ft = ________ yd  ft yd 3 1 5 Calculate the answer. Multiply across the top. Multiply across the bottom of the expression. Divide the bottom by the top Enter into the calculator: 52  1  3 17.33

75. Example #2 Example: How many grams are equal to 127.0 mg? 127.0 mg 1 Write down your given information

76. Example #1 Example: How many grams are equal to 127.0 mg? 127.0 mg 2 Write down an answer blank and the desired unit on the right side of the problem space = ________ g

77. Example #1 Example: How many grams are equal to 127.0 mg? 127.0mg = ________ g 3 &4 Use or create a conversion factor to compare what you have to what you want The equivalent with these 2 units is: 1 g = 1000 mg A tip is to arrange the units first and then fill in numbers later!  mg g Put the unit on bottom that you want to cancel out! 1000 1

78. Example #1 Example: How many grams are equal to 127.0 mg? 127.0 mg = ________ g  mg g 1000 1 5 Calculate the answer. Multiply across the top. Multiply across the bottom of the expression. Divide the bottom by the top Enter into the calculator: 127  1  1000.127

79. Metric Conversion Factors Many students get confused where to put the number shown in the previous chart… 1.Select which unit is greater. 2.Make that unit 1 and then determine how many smaller units are in the bigger unit. 1 kg = 1000 g my way OR.001Kg = 1 g the other way Example: Write a correct equivalent between “kg” and “g”

80. Try More Metric Equivalents There are two options: 1 L = 1000 ml my way 0.001 L = 1 mL the other way Example: Write a correct equivalent between “mL” and “L” There are two options: 1 cm = 10 mm my way.1cm = 1mm the other way Example: Write a correct equivalent between “cm” and “mm”

81. Multi-step problems There isn’t always an equivalent that goes directly from where you are to where you want to go! With multi-step problems, it’s often best to plug in units first, then go back and do numbers.

82. Example #3 Example: How many kilograms are equal to 345 cg? 345 cg = _______ kg There is no direct equivalent between cg & kg With metric units, you can always get to the base unit from any prefix! And you can always get to any prefix from the base unit! You can go from “cg” to “g” Then you can go from “g” to “kg”

83. 345 cg = _______ kg Example #3 Example: How many kilograms are equal to 345 cg?  cg g Go to the base unit  g kg Go from the base unit

84. = _______ kg Example #3 Example: How many kilograms are equal to 345 cg?  cg g 100 1 345 cg  g kg 1000 1 100 cg = 1 g 1000 g = 1 kg Remember—the # goes with the base unit & the “1” with the prefix!

85. = _______ kg Example #3 Example: How many kilograms are equal to 345 cg?  cg g 100 1 Enter into the calculator: (345  1 x 1)  (100 x 1000) 0.00345 345 cg  g kg 1000 1

86. You Try! #1 Example: 0.250 kg is equal to how many grams?

87. 1000 0.250 kg You Try! #1 Example: 0.250 kg is equal to how many grams? = ______ g  kg g 1 1 kg = 1000 g Enter into the calculator: 0.250  1000  1 250.

88. Last One! NOT in YOUR NOTES Example: How many mL is equal to 2.78 L?

89. 1000 2.78 L Example: How many mL is equal to 2.78 L? = ______ mL  L mL 1 1 mL = 0.001 L Enter into the calculator: 2.78  1000  1 2780

90. Metric Volume Units To find the volume of a cube, measure each side and calculate: length  width  height length height width But most chemicals aren’t nice, neat cubes! Therefore, they defined 1 milliliter as equal to 1 cm 3 (the volume of a cube with 1 cm as each side measurement) 1 cm 3 1 mL =

91. You Try! #3 Example: 147 cm 3 is equal to how many liters?

92. You Try! #3 Example: 147 cm 3 is equal to how many liters? Remember—cm 3 is a volume unit, not a length like meters! = _______ L  cm 3 mL 1 1 147 cm 3  mL L 1000 1 There isn’t one direct equivalent 1 cm 3 = 1 mL 1 L = 1000 mL or.001L = 1mL Enter into the calculator: 147  1  0.001  1  1 0.147

93. Section 1.4—Scientific Notation

94. Scientific Notation Scientific Notation is a form of writing very large or very small numbers that you’ve probably used in science or math class before Scientific notation uses powers of 10 to shorten the writing of a number.

95. Writing in Scientific Notation The decimal point is put behind the first non-zero number The power of 10 is the number of times it moved to get there A number that began large (>1) has a positive exponent & a number that began small (<1) has a negative exponent

96. Example #1 Example: Write the following numbers in scientific notation. 240,000 m 0.0000048 g

97. Example #1 Example: Write the following numbers in scientific notation. 240,000 m 0.0000048 2.4  10 m 5 6.5423  10 g -6 The decimal is moved to follow the first non-zero number The power of 10 is the number of times it’s moved

98. Reading Scientific Notation A positive power of ten means you need to make the number bigger and a negative power of ten means you need to make the number smaller Move the decimal place to make the number bigger or smaller the number of times of the power of ten

99. Example #2 Example: Write out the following numbers. 5.3  10 7 m 53000000 m

100. Example #3 Example: Write out the following numbers in scientific notation. 123000000 0.000987 0.000000045 480000000000 0.00000612 1.23 x 10 8 9.87 x 10 -4 4.5 x 10 -8 4.8 x 10 11 6.12 x 10 -6

101. Example #3 Example: Write out the following numbers in ordinary notation. 3.4  10 -9 m 1.12  10 5 m 2.347  10 7 g 8.9  10 -3 g 7.23  10 -12 m.0000000034 112000 23470000.0089.00000000000723

102. HONORS ONLY: Scientific Notation & Significant Digits Scientific Notation is more than just a short hand. Sometimes there isn’t a way to write a number with the needed number of significant digits …unless you use scientific notation!

103. How to enter scientific notation numbers into the calculator 1. Punch the digit number into your calculator. 2. Push EE or EXP button. (Do not use the x(times) button. 3. Enter the exponent number. Use the +/- button to change its sign. Example: Multiply 6.0 x10 5 times 4.0 x10 3 on your calculator. Your answer is: 240000000 or 2.4 x 10 9