Modern Chemistry Chapter 2 Measurements and Calculations Sections 1 - 3 Scientific Method Units of Measurement Using Scientific Measurements

Chapter 2 Section 1 Scientific Method pages 29-32 System Hypothesis Model Theory Quantity SI Weight Derived unit Volume Density Conversion Factor Dimensional analysis Accuracy Precision Percentage error Significant figures Scientific notation Directly proportional Inversely proportional Chapter Vocabulary Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 1 Scientific Method pages 29-32 A logical approach to solving problems by OBSERVING AND COLLECTING DATA FORMULATING HYPOTHESIS TESTING HYPOTHESIS FORMULATING THEORIES that are supported by data. Not a fixed series of steps. Chapter 2 Section 1 Scientific Method pages 29-32

Scientific Method Image p. 31 Chapter 2 Section 1 Scientific Method pages 29-32

Scientific Method Animation Chapter 2 Section 1 Scientific Method pages 29-32

Observation and Collecting Data What are we studying? A system is a specific portion of matter in a given region of space that has been selected for study during an experiment or observation. Chapter 2 Section 1 Scientific Method pages 29-32

Observation and Collecting Data use of senses to obtain information Qualitative – descriptive Quantitative – numeric Organize data and observations into tables and/or graphs. Chapter 2 Section 1 Scientific Method pages 29-32

Organizing Data into a Graph Chapter 2 Section 1 Scientific Method pages 29-32

Qualitative and Quantitative Observation Animation Chapter 2 Section 1 Scientific Method pages 29-32

Formulating Hypothesis Generalizations about data or observations can be used to make a hypothesis A hypothesis is a testable statement Often in an if-then statement A prediction that is the basis for testing by experiment Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 1 Scientific Method pages 29-32 Hypothesis Animation Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 1 Scientific Method pages 29-32 Testing Hypothesis Controls – conditions that remain constant (controlled variables) Variable – any condition that changes Driven by the hypothesis Test only one variable at a time Identify variables to be held constant Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 1 Scientific Method pages 29-32 Theorizing When data from experiments support a hypothesis a theory and model are constructed A model in science is more than a physical object. It is often an explanation of how phenomena occur and how data or events are related Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 1 Scientific Method pages 29-32 Model Animation Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 1 Scientific Method pages 29-32 Theorizing Models are a part of a theory. A theory is a broad generalization that explains a body of facts or phenomena. not a fact; explains facts modified with new discoveries Chapter 2 Section 1 Scientific Method pages 29-32

Reading Notes #7-15 pages 33-43 Section 1 Homework Reading Notes #7-15 pages 33-43 Chapter 2 Section 1 Scientific Method pages 29-32

Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 QUANTITY UNIT STANDARD Length Foot The king’s foot Mass Kilogram Kg prototype a.m.u. 1/12th of a carbon-12 atom Something that has magnitude, size or amount Objects or natural phenomena that are of constant value, easy to preserve and reproduce Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Common SI Units Table p. 33* Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 SI Measurements Le Systeme’ International d’Unites 75 000 not 75,000 use spaces not commas Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Base SI Units Table p. 34 Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 SI Base Units Comparing Mass and Weight Mass is the measure of the amount of mater in an object. Unit = kg Weight is the measure of the gravitational pull on matter Unit = N (newtons) Dependant on gravity Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 SI Prefixes giga G 1 Gm = 1 x 109 m mega M 1 Mm = 1 x 106 m kilo k 1 km = 1000 m hecto h 1 hm = 100 m deka da 1 dam = 10 m 1 m = 1 meter deci d 1 dm = 0.1 m centi c 1 cm = 0.01m milli m 1 mm = 0.001m micro μ 1 μm = 1 x 10-6 m nano n 1 nm = 1 x 10 -9 m Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 SI Conversions Image p. 40* Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Derived SI Units Derived Units – a combination of SI units Example 1 kg/m∙sec2 = 1 pascal (Pa) Volume – the amount of space occupied by an object L x W x H = 1m x 1m x 1m = 1m3 1dm x 1dm x 1dm = 1dm3 = 1 liter 1cm x 1cm x 1cm = 1cm3 = 1 mL Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Derived Units Table p. 36 Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Density The ratio of mass to volume D = M / V Unit = kg/m3 or g/cm3 = g/mL A characteristic physical property Can be used to identify a substance Varies with temperature Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Density Table p. 38 Chapter 2 Section 2 Units of Measurements pages 33-43

Density Formula Animation Chapter x Section x Section title pages xx-xx

Chapter 2 Section 2 Units of Measurements pages 33-43 Density What is the density of a block of marble that occupies 310 cm3 and has a mass of 853 g? Diamond has a density of 3.26g/cm3. What is the mass of a diamond that has a volume of 0.351 cm3? What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given the density of mercury is 13.6 g/mL? p. 40 1. 2.75 g/cm3 2. 1.14 g 3. 5.60 mL Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Conversion Factors A ratio derived from the equality between two different units that can be used to convert from one unit to another Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Conversion Factors Conversion factors always equal 1. The numerator is equal to the denominator. 4 quarters 1 dollar = 1 1 kilogram 1000 grams = 1 12 inches 1 foot = 1 Chapter 2 Section 2 Units of Measurements pages 33-43

Conversion Factors Animation Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Dimensional Analysis A mathematical technique that allows you to use units to solve a problem involving measurements Chapter 2 Section 2 Units of Measurements pages 33-43

Dimensional Analysis wanted unit # given unit = # wanted unit x Put in numbers to make the numerator equal to the denominator = # wanted unit x given unit Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Dimensional Analysis x x x x = Arrange the units so that all cancel out except the last one, which should be the one you want. Chapter 2 Section 2 Units of Measurements pages 33-43

Using Conversion Factors Image p. 40* Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Dimensional Analysis How many seconds in one week? Chapter 2 Section 2 Units of Measurements pages 33-43

Chapter 2 Section 2 Units of Measurements pages 33-43 Dimensional Analysis Express a length of 16.45 m in centimeters and in kilometers. Express a mass of 0.014 mg in grams. p. 40 1. 1645 cm and 0.01645 km 2. 0.000 014 g Chapter 2 Section 2 Units of Measurements pages 33-43

Using Scientific Measurements Section 3 Using Scientific Measurements Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Accuracy and Precision Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured Precision refers to the closeness of a set of measurements of the same quantity made the same way. Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Accuracy & Precision Darts Animation Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Accuracy and Precision Image Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Chapter 2 Section 3 Using Scientific Measur. pages 44-57 Percent Error High percent error = low accuracy Negative? Experimental is too low Positive? Experimental is too high Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Percent Error Formula Animation Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Chapter 2 Section 3 Using Scientific Measur. pages 44-57 Percent Error Express a length of 16.45 m in centimeters and in kilometers. Express a mass of 0.014 mg in grams. p. 40 1. 1645 cm and 0.01645 km 2. 0.000 014 g Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Chapter 2 Section 3 Using Scientific Measur. pages 44-57 Errors in Measurement Skill of the measurer Limitation of instruments Estimation Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Measuring Liquids & Meniscus Animation Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Chapter 2 Section 3 Using Scientific Measur. pages 44-57 certain estimated Plus or minus one of the estimated decimal places p. 46 Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Affectionately called “sig. figs.” SIGNIFICANT FIGURES SIGNIFICANT FIGURES Affectionately called “sig. figs.”

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Nonzero integers always count as significant figures!

All the certain number in a measurement plus one estimated figure. Significant Figures All the certain number in a measurement plus one estimated figure.

There are three classes of zeros. http://www.youtube.com/watch?v=Nvc2PPTlW7k There are three classes of zeros. LEADING TRAILING CAPTIVE

as significant figures. LEADING ZEROS These do not count as significant figures. 0.0025 2.5 x 10-3

as significant figures. CAPTIVE ZEROS These count as significant figures. 1.008

100 vs. 100. 1.00 x 102 TRAILING ZEROS These do not count as significant figures… unless there is a decimal point. 100 vs. 100. 1.00 x 102

2 atoms of H in H2O EXACT NUMBERS These are determined by counting. These have infinite significant figures. 2 atoms of H in H2O

These answer the question, “What do we round to?” SIG FIGS IN CALCULATIONS These answer the question, “What do we round to?” There are two different rules: Multiplication & Division Addition & Subtraction

A team is only as good as its…. PRECISION A team is only as good as its…. worst player Practice! Your answer can only be as precise as your least precise (worst) piece of data!

MULTIPLICATION & DIVISION The number of sig figs in the result is the same as the least precise measurement used in the calculation. 13.54g /0.40ml = 34 g/ml 33.85 g/ml

ADDITION & SUBTRACTION The result has the same number of decimal places as the least precise measurement used in the calculation. 13.85 + 0.0087 = 13.8587 13.86 +

In a series of calculations, round at the very end. Rounding In a series of calculations, round at the very end. LESS THAN The preceding digit stays the same. 5 & GREATER The preceding digit is increased by 1. 5

Significant Figures Rules Table p. 47 Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Rules for Significant Zeros Animation Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Rounding Rules Animation Chapter 2 Section 3 Using Scientific Measur. pages 44-57

M x 10n Scientific Notation Greater than or equal to 1 but less than 10 A whole number A negative exponent means the number is small A positive exponent means the number is large Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Chapter 2 Section 3 Using Scientific Measur. pages 44-57 Scientific Notation What is the volume, in milliliters, of a sample of helium that has a mass of 1.73 x 10-3 g, given that the density is 0.178 47 g/L? What is the density of a piece of metal that has a mass of 6.25 x 105 g and is 92.5cm x 47.3 cm x 85.4 cm? p. 54 1. 9.69 mL 2. 1.67 g/cm3 Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Chapter 2 Section 3 Using Scientific Measur. pages 44-57 Scientific Notation How many millimeters are there in 5.12 x 105 kilometers? A clock gains 0.020 second per minutes. How many seconds will the clock gain in exactly six months, assuming exactly 30 days per month? p. 54 1. 5.12 x 1011 mm 2. 5.2 x 103 sec Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Direct Proportions Two quantities are directly proportional to each other if dividing on by the other gives a constant value As Y increases; X increases Y X = k Y = k X The equation for a line! k is the slope. Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Directly Proportional Graph The line must go through the origin to be directly proportional p. 55 Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Chapter 2 Section 3 Using Scientific Measur. pages 44-57 Inverse Proportions Two quantities are inversely proportional to each other if their product is constant. As X increases; Y decreases X Y = k produces a curve – a hyperbola Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Inversely Proportional Graph Chapter 2 Section 3 Using Scientific Measur. pages 44-57

Directly Proportional & Inversely Proportional Graph Animation Chapter 2 Section 3 Using Scientific Measur. pages 44-57