1. Pre-IB/Pre-AP CHEMISTRY
Chapter 2 – Measurements and Calculations

2. Section 1: Scientific Method
_____________ is a process whose goal is to discover facts about the universe.
Most scientific advances result form carefully planned ____________________.
Science relies on observation, experimentation, and experience

3. Section 1: Scientific Method
Science is a process whose goal is to discover facts about the universe.
Most scientific advances result form carefully planned investigations.
Science relies on observation, experimentation, and experience

4. Section 1: Scientific Method
The process researches use to carry out their investigations is called the _________ ________ .
This is a a logical approach to solving problems by ______________ and ______________ _______, ________________ ____________, _______________ hypotheses and formulating ________________ that are supported by data.
The scientific method is ___________________, repeatable and testable.

5. Section 1: Scientific Method
The process researches use to carry out their investigations is called the scientific method.
This is a a logical approach to solving problems by ______________ and ______________ _______, ________________ ____________, _______________ hypotheses and formulating ________________ that are supported by data.
The scientific method is ___________________, repeatable and testable.

6. Section 1: Scientific Method
The process researches use to carry out their investigations is called the scientific method.
This is a a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses and formulating theories that are supported by data.
The scientific method is ___________________, repeatable and testable.

7. Section 1: Scientific Method
The process researches use to carry out their investigations is called the scientific method.
This is a a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses and formulating theories that are supported by data.
The scientific method is systematic, repeatable and testable.

8. Section 1: Scientific Method
I. Observing and Collecting Data
__________________ – the use of the senses to obtain information. Observation involves making measurements and collecting data.
Two types of data:
________________– descriptive in nature; _____- _____________ information (ex. the sky is blue)
_________________ - __________________ in nature; (ex. 5 meters long)

9. Section 1: Scientific Method
I. Observing and Collecting Data
Observing – the use of the senses to obtain information. Observation involves making measurements and collecting data.
Two types of data:
________________– descriptive in nature; _____- _____________ information (ex. the sky is blue)
_________________ - __________________ in nature; (ex. 5 meters long)

10. Section 1: Scientific Method
I. Observing and Collecting Data
Observing – the use of the senses to obtain information. Observation involves making measurements and collecting data.
Two types of data:
Qualitative– descriptive in nature; non-numerical information (ex. the sky is blue)
_________________ - __________________ in nature; (ex. 5 meters long)

11. Section 1: Scientific Method
I. Observing and Collecting Data
Observing – the use of the senses to obtain information. Observation involves making measurements and collecting data.
Two types of data:
Qualitative– descriptive in nature; non-numerical information (ex. the sky is blue)
Quantitative – numerical in nature; (ex. 5 meters long)

12. Section 1: Scientific Method
I. Observing and Collecting Data
Experimenting involves carrying out a procedure under controlled __________________ to make observations and collect data.
Chemists study ________________ – a specific portion of matter in a given region of space that has been selected for ___________ during an experiment or observation.

13. Section 1: Scientific Method
I. Observing and Collecting Data
Experimenting involves carrying out a procedure under controlled conditions to make observations and collect data.
Chemists study ________________ – a specific portion of matter in a given region of space that has been selected for ___________ during an experiment or observation.

14. Section 1: Scientific Method
I. Observing and Collecting Data
Experimenting involves carrying out a procedure under controlled conditions to make observations and collect data.
Chemists study systems – a specific portion of matter in a given region of space that has been selected for study during an experiment or observation.

15. Section 1: Scientific Method
II. Formulating Hypotheses
Scientists examine and compare data from their experiments to attempt to find relationships and ______________ – they try to make generalizations based on the data.
___________________ - statements that apply to a ___________ of information. Data is sometimes organized into tables and analyzed using statistics/mathematical techniques.

16. Section 1: Scientific Method
II. Formulating Hypotheses
Scientists examine and compare data from their experiments to attempt to find relationships and patterns – they try to make generalizations based on the data.
___________________ - statements that apply to a ___________ of information. Data is sometimes organized into tables and analyzed using statistics/mathematical techniques.

17. Section 1: Scientific Method
II. Formulating Hypotheses
Scientists examine and compare data from their experiments to attempt to find relationships and patterns – they try to make generalizations based on the data.
Generalizations- statements that apply to a range of information. Data is sometimes organized into tables and analyzed using statistics/mathematical techniques.

18. Section 1: Scientific Method
II. Formulating Hypotheses
Scientists then use these generalizations to formulate a ________________ – a testable statement; _________________ __________. The hypothesis serves as basis for making ________________ and for carrying out further experiments.
Hypotheses are often “___ - _________” statements – the “then” part is a prediction that is the basis for testing by experiment.

19. Section 1: Scientific Method
II. Formulating Hypotheses
Scientists then use these generalizations to formulate a hypothesis – a testable statement; an educated guess. The hypothesis serves as basis for making predictions and for carrying out further experiments.
Hypotheses are often “___ - _________” statements – the “then” part is a prediction that is the basis for testing by experiment.

20. Section 1: Scientific Method
II. Formulating Hypotheses
Scientists then use these generalizations to formulate a hypothesis – a testable statement; an educated guess. The hypothesis serves as basis for making predictions and for carrying out further experiments.
Hypotheses are often “if - then” statements – the “then” part is a prediction that is the basis for testing by experiment.

21. Section 1: Scientific Method
III. Testing Hypotheses
Testing a hypothesis requires _____________________ that provides data to ____________ or ___________ a hypothesis or theory.
If testing reveals that predictions were NOT correct, the hypothesis must be ______________ or _____________.
Hypotheses can be proven ______________ and they can be supported/proven ______________, but they CANNOT be proven correct.

22. Section 1: Scientific Method
III. Testing Hypotheses
Testing a hypothesis requires experimentation that provides data to support or refute a hypothesis or theory.
If testing reveals that predictions were NOT correct, the hypothesis must be ______________ or _____________.
Hypotheses can be proven ______________ and they can be supported/proven ______________, but they CANNOT be proven correct.

23. Section 1: Scientific Method
III. Testing Hypotheses
Testing a hypothesis requires experimentation that provides data to support or refute a hypothesis or theory.
If testing reveals that predictions were NOT correct, the hypothesis must be discarded or modified.
Hypotheses can be proven ______________ and they can be supported/proven ______________, but they CANNOT be proven correct.

24. Section 1: Scientific Method
III. Testing Hypotheses
Testing a hypothesis requires experimentation that provides data to support or refute a hypothesis or theory.
If testing reveals that predictions were NOT correct, the hypothesis must be discarded or modified.
Hypotheses can be proven incorrect and they can be supported/proven successful, but they CANNOT be proven correct.

25. Section 1: Scientific Method
III. Testing Hypotheses
____________ – Experimental conditions that remain ______________ during testing.
______________ – any conditions that __________ during testing.
Any changes observed are due to the effects of the variable.
Might affect the outcome of the experiment

26. Section 1: Scientific Method
III. Testing Hypotheses
Controls – Experimental conditions that remain constant during testing.
______________ – any conditions that __________ during testing.
Any changes observed are due to the effects of the variable.
Might affect the outcome of the experiment

27. Section 1: Scientific Method
III. Testing Hypotheses
Controls – Experimental conditions that remain constant during testing.
Variables – any conditions that change during testing.
Any changes observed are due to the effects of the variable.
Might affect the outcome of the experiment

28. Section 1: Scientific Method
III. Testing Hypotheses
Two types of variables:
_______________ - the variable that is manipulated by the experimenter. There should only be ______ in an experiment.
_______________ - variable that is studied. It is expected to change as a result of changes in the ________________ variable. There may be more than one dependent variable.

29. Section 1: Scientific Method
III. Testing Hypotheses
Two types of variables:
Independent - the variable that is manipulated by the experimenter. There should only be ONE in an experiment.
_______________ - variable that is studied. It is expected to change as a result of changes in the ________________ variable. There may be more than one dependent variable.

30. Section 1: Scientific Method
III. Testing Hypotheses
Two types of variables:
Independent - the variable that is manipulated by the experimenter. There should only be ONE in an experiment.
Dependent - variable that is studied. It is expected to change as a result of changes in the independent variable. There may be more than one dependent variable.

31. Section 1: Scientific Method
III. Testing Hypotheses
Two groups:
Control group - allows you to observe what is considered “normal” under a specific set of conditions, so comparisons can be made with the experimental group.
Experimental group – this group experiences a change in one variable. Only one variable should be changed at a time

32. Section 1: Scientific Method
IV. Theorizing
When data shows that the predictions of a hypothesis are successful, scientist then typically try to explain the phenomena they are studying by constructing a ___________– more than just a physical object, it is often an ____________________ of how phenomena occur and how data or events are _____________.
Models may be _____________, verbal or _____________________.

33. Section 1: Scientific Method
IV. Theorizing
When data shows that the predictions of a hypothesis are successful, scientist then typically try to explain the phenomena they are studying by constructing a model – more than just a physical object, it is often an explanation of how phenomena occur and how data or events are related.
Models may be _____________, verbal or _____________________.

34. Section 1: Scientific Method
IV. Theorizing
When data shows that the predictions of a hypothesis are successful, scientist then typically try to explain the phenomena they are studying by constructing a model – more than just a physical object, it is often an explanation of how phenomena occur and how data or events are related.
Models may be visual, verbal or mathematical.
Ex. Atomic model of matter – states that matter is composed of tiny particles – atoms

35. Section 1: Scientific Method
IV. Theorizing
______________– a broad generalization that explains a body of facts or phenomena.
If a model successfully explains many phenomena, it may become part of a theory.
Theories are considered successful if they can ___________ the ___________ of many new experiments.

36. Section 1: Scientific Method
IV. Theorizing
Theory– a broad generalization that explains a body of facts or phenomena.
If a model successfully explains many phenomena, it may become part of a theory.
Theories are considered successful if they can ___________ the ___________ of many new experiments.

37. Section 1: Scientific Method
IV. Theorizing
Theory– a broad generalization that explains a body of facts or phenomena.
If a model successfully explains many phenomena, it may become part of a theory.
Theories are considered successful if they can predict the results of many new experiments.

38. Section 1: Scientific Method
IV. Theorizing
Theory– a broad generalization that explains a body of facts or phenomena.
Ex. Kinetic-Molecular Theory – Theory that explains that the behavior of physical systems depends on the combined actions of the molecules constituting the system
Ex. Collision Theory – Theory that states that the number of new compounds formed in a chemical reaction is = to the number of molecules that collide

39. Section 1: Scientific Method
IV. Theorizing
___________________ gives scientists an opportunity to ______________ the work of others and see if they get the _________ _______________.
Others will be able to duplicate valid work.

40. Section 1: Scientific Method
IV. Theorizing
Publication gives scientists an opportunity to repeat the work of others and see if they get the same results.
Others will be able to duplicate valid work.

41. Section 1: Scientific Method
Question
Research
Hypothesis
Experiment
Analysis
Conclusion

42. Section 2 Objectives
Be able to define: quantity, measurement, standard, length, mass, weight, derived unit, volume, density, conversion factor.
Be able to state the units of mass, length, temperature, and time in the SI system.

43. Section 2 Objectives
Be able to explain the difference between mass and weight.
Be able to state the meaning of common prefixes used in the SI system (Deka-, Hecto- , Kilo-, Mega-, Giga-, deci-, centi-, milli-, micro-, nano-.
Be able to convert units within the SI system.

45. Measurement Measurements represent quantities.
A quantity is something that has magnitude, size, or amount.

46. Measurement
Measurements and quantities are not the same. Example: A teaspoon is a unit of measurement for volume (a quantity).

47. Units of Measurement
Units of measurement vary from place to place. Using all of them would lead to confusion in reporting scientific investigations.

48. SI System
In 1960, scientists agreed to use Le Système International d’Unités or the SI system of measurement.

49. SI System
The SI system defines 7 base units for length, mass, time, temperature, amount of a substance, etc.

50. Standards
The SI system defined standards for every base unit that can be replicated (Table 1, Pg. 34).

51. SI Base Units Quantity Quantity Symbol Unit Name Unit abbreviation 1
Length l
Meter m 2
Mass
Kilogram kg 3
Time t
Second s 4
Temperature T
Kelvin K 5
Amount of Substance n
Mole
mol

52. Length
Length is the distance between two points. SI unit =meter

53. Mass
Mass is the amount of matter contained in an object. SI unit = kilogram

54. Weight
Weight is the gravitational pull on a given mass. It is a unit of force not mass.

55. Weight and Mass
Weight will vary according to the position of an object in the universe. The mass of that object is always the same.

56. Derived Units m2 m Example: Area = L x W Area = m x m Area = m2
Derived units are combinations of base SI units. Table 3, Pg. 36
Example:
Area = L x W
Area = m x m
Area = m2 m2 m

57. Volume
Volume is the amount of space occupied by an object. SI unit = Liter (dm3)

58. Density
Density is the ratio of mass to volume. Its units are derived from some unit of mass divided by some unit of volume (g/mL, Kg/m3). (Sample Problem A, pg. 39)

59. Conversions
Making conversions within the SI system is easy since it is based on powers of ten, like our counting system.

60. Conversions
If you understand the meaning of common prefixes, you can convert units by simply moving a decimal point.
The SI sytsem uses Greek words as prefixes for multiples of a unit and Latin words as prefixes for divisions of a unit.

61. Conversions GREEK LATIN 10 Deka- 10 x deci- 1/10 100 Hecto- 100 x
centi-
1/100
1000
Kilo-
milli-
1/1000
Million
Mega-
Million x
micro-
millionth
Billion
Giga-
Billion x
nano-
billionth

63. Conversion Factors 1 m 100 cm 100 cm 1 m
A conversion factor is a ratio derived from the equality between two different units that can be used to convert from one unit to another. (Sample Problem B, pg. 41)
100 cm
1 m
100 cm
1 m

64. Chapter 2-3 Objectives
Be able to define: accuracy, precision, percent error, significant figures, scientific notation, conversion factor, hyperbola.
Be able to distinguish between accuracy and precision.
Be able to determine the number of significant figures in a measurement.

65. Chapter 2-3 Objectives
Be able to perform mathematical operations and express the result in the proper number of significant figures.
Be able to convert measurements into scientific notation.
Be able to distinguish between inversely and directly proportional.

66. Chapter 2-3 Objectives
Be able to perform calculations involving measurements (addition, subtraction, multiplication, division) and express the result in the proper number of significant figures and the proper units.

67. Measurements
Scientists like to deal with precise and accurate measurements.

68. Accuracy
Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured (Does it hit the bull’s eye?).

69. Precision
Precision refers to the closeness of a set of measurements of the same quantity made in the same way.

70. Problem Describe what you see in terms of accuracy and precision.
High Accuracy
High Precision

71. Problem Describe what you see in terms of accuracy and precision.
Low Accuracy
High Precision

72. Problem Describe what you see in terms of accuracy and precision.
Low Accuracy
Low Precision

73. High Accuracy (on average)
Problem
Describe what you see in terms of accuracy and precision.
High Accuracy (on average)
Low Precision

74. Error
Scientists use a number of statistical tests to see how well their data compare to their expected results.

75. Percent Error
Percent error is calculated by subtracting the experimental value from the accepted value, dividing the difference by the accepted value, and then multiplying by 100.
Percent Error =
x 100
Valueexperimental – Valueaccepted
Valueaccepted

76. Percent Error
Percent error may be a positive or a negative number based on the difference between the experimental and accepted values.
Sample Problem C, Pg. 45

77. Measurements
Every measuring device has values marked on it or provides you with a readout.
The only values you know for certainty are those marked on the device or presented in the readout.
(Next Slide)

79. Measurements
In science, measured values are reported in terms of significant figures.
Significant figures in a measurement consist of all the digits known with certainty plus one final digit, which is somewhat uncertain.
The term significant does not mean certain.

80. This is Imperative
You MUST use and recognize significant figures when you work with measured quantities and report your results, and when you evaluate measurements reported by others. So, LEARN THE RULES FOR DETERMINING SIGNIFICANT FIGURES.

81. Rules 1. All nonzero digits are significant.
2. All zeros between two nonzero digits are significant( Km, 40.7 L).
Zeros at the end of a number and to the right of a decimal point are significant.(85.00 g, mm).

82. Rules cont’d
4. Zeros at the end of a number but to the left of a decimal point may or may not be significant. If a zero has not been measured or estimated but is a placeholder, it is not significant. A decimal point placed after zeros indicates that they are significant.
5. Conversion factors have an unlimited number of significant figures (1 Km = 1000 m).

83. How many significant figures?
Problem D, pg. 47
28.6 g
3440. cm
910 m L Kg

84. How many significant figures?
Practice Prob. 1, pg. 48 g Km
1002 m
400 mL cm Kg

85. Problem Practice Prob. 2, pg. 48
Suppose the value “seven thousand centimeters” is reported to you. How should the number be expressed if it is intended to contain the following:
1 sig. fig.
4 sig. figs.
6 sig. figs.
(7000 cm)
(7000. cm)
( cm)

86. Rounding Rules
When doing calculations with measurements, you will need to round to a certain number of significant figures. Learn the rounding rules on pg. 48.

87. Results of Calculations
When performing calculations involving measurements certain rules apply whether you are adding, subtracting, multiplying, or dividing. FOLLOW THOSE RULES.
(Next Slide)

88. Addition and Subtraction
Place all measurements in a column.
Find the rightmost place where there is a digit for each number.
Round all measurements to that place, then add or subtract.

89. Addition and Subtractioncm cm cm
0.006 cm + cm

90. Multiplication and Division
Count the number of significant figures in each measurement.
Round your answer to the number of significant figures in the measurement with the LEAST number of significant figures.
3.05 g
8.47 mL
D =
= g/mL = g/mL

91. Scientific Notation
The numbers we deal with in science can be extremely small or extremely large.
Converting to scientific notation or exponential notation makes handling these numbers much easier.

92. Scientific Notation
In scientific notation, numbers are written in the form of M x 10n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.
Example: 6.02 x 1023 atoms/mole
Incorrect: 60.2 x 1022 or .602 x 1024

93. Addition and Subtraction
Convert all numbers to the same power of 10.
Add or Subtract all the coefficients (M’s).
Convert the sum to proper notation form.

94. Multiplication Multiply coefficients (M’s) Add exponents
Convert to proper notation form

95. Division Divide coefficients (M’s) Subtract exponents
Convert to proper notation form

96. Problem Solving
Analyzing and solving problems is an integral part of Chemistry. You must follow a logical approach to solving problems in Chemsitry.
Analyze the Problem - read the problem at least twice to analyze the information in the problem. If you don’t understand it read it again.

97. Problem Solving Develop a plan for solving the problem.
Substitute the data and necessary conversion factorsinto the plan you have developed.
Examine your answer to determine whether it is reasonable.
(Sample Prob. F, pg. 54)

98. Direct Proportions
Two quantities are directly proportional to each other if dividing one by the other gives a constant value.

99. Inverse Proportions
Two quantities are inversely proportional to each other if their product is constant.

100. Inverse Proportion
A graph of variables that are inversely proportional produces a curve called a hyperbola.

101. THE END