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Published byDorothy Maxwell Modified over 9 years ago
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Data Analysis Applying Mathematical Concepts to Chemistry
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Units of Measure SI Units- scientifically accepted units of measure:
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The Metric System
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Metric Practice 623.19 hL = __________ L 1026 mm = ___________cm 0.025 kg = ___________mg Online Powers of 10 Demonstration: http://micro.magnet.fsu.edu/primer/java/science opticsu/powersof10/
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Derived Quantities- Volume Volume- amount of space an object takes up. V = l x w x h (all in meters) V= m 3 m 3 is too large so cm 3 are used 1 cm 3 = 1 mL by definition
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Temperature Scales
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Temperature Conversions Degrees Celsius to Kelvin T kelvin =T celsius + 273 EX: 25 °C = ? K T kelvin =25 +273=298K Kelvin to Degrees Celsius T celsius =T kelvin - 273 EX: 210 K = ? °C T c = 273–210= -63°C
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Scientific Notation A method of expressing very large or small numbers in a concise manner Requires 2 parts: – Number between 1 and 9.99999999… – Power of ten – EX: 5432.1 meters 5.4321 x 10 3 meters
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Factor Labeling (Dimensional Analysis) Any number divided by itself is equal to 1 – 6/6 = 1 – 6 meters/6 meters = 1 Any number can be multiplied by one without changing its value – 5 x (6/6) = 5 – 5 x (6 meters/6 meters) = 5
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Converting Units Through Dimensional Analysis Equal units divided by one another are equal to 1 1m/100 cm = 1 m/cm 100 cm/1m = 1 cm/m 50 cm x (1m/100cm) = 0.5 m 50 m x (100cm/1m) = 5000 cm
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Practice Problems 12.5 eggs = ? Dozen 13.69 m = ? cm 13.69 km = ? cm 1.25 x 10 3 ft = ? yd
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Multiple Step Factor Labeling 5.2 x10 3 yd = ? In 45 mph = ? ft/min 3.1 g/mL = ? Kg/L
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Derived Quantities- Density Density- how much matter is in the volume an object takes up. Density = mass/volume D= g/mL
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Determining Density Mass- measure in grams with balance Volume- – Regular shaped object: measure sides and use volume formula EX: rectangle V= l x w x h – Irregular shaped object: water displacement
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Density by Water Displacement Fill graduated cylinder to known initial volume Add object Record final volume Subtract initial volume from final volume Record volume of object
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Graphing Data General Rules – Fit page – Even scale – Best fit/trendline – Informative Title – Labeled Axes How Does Volume Impact Temperature?
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Accuracy vs Precision Accuracy- closeness of measurements to the target value Precision- closeness of measurements to each other
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Percent Error %error = (accepted-experimental) x 100 accepted EX: The measured mass is 5.0g. It was predicted that the accepted value should have been 6.0 g. % error = 6.0g-5.0g x 100 = 16.7% 6.0g
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Significant Figures Measurements are limited in their sensitivity by the instrument used to measure
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Estimating Measurements Read one place past the instrument 35.0 mL is saying the actual measurement is between 34.9 and 35.1 mL
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Why Significant Figures? Measurements involve rounding Multiplying/dividing or adding/subtracting measurements can not make them more accurate Provide a way to tell how sensitive a measurement really is… 5 ≠ 5.0 ≠ 5.00 ≠ 5.000
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Recognizing Significant Digits 1. Nonzero digits are always significant – 543.21 meters has 5 significant figures 2. Zeros between nonzeros are significant – 505.05 liters has 5 sig figs 3. Zeros to the right of a decimal and a nonzero are significant – 3.10 has 3 sig figs
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Recognizing Sig Figs 4. Placeholder zeros are not significant – 0.01g has one sig fig – 1000g has one sig fig – 1000.g has four sig figs – 1000.0g has five sig figs 5. Counting numbers and constants have infinite significant figures – 5 people has infinite sig figs
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Practice Identifying Sig Figs A) Clearly circle the significant digits in each of the following numbers: 0.540 30 m 46.93 L 0.004 79 g 56.00 s B) Rewrite each of the following numbers to the number of significant digits which is specified in the parenthesis: 0.012 70 (2)2,190,050 L (2) 0.005 23 g (1)3.079 s (2)
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Rule for Multiplying/Dividing Sig Figs Multiply as usual in calculator Write answer Round answer to same number of sig figs as the lowest original operator EX: 1000 x 123.456 = 123456 = 100000 EX: 1000. x 123.456 = 123456 = 123500
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Practice Multiplying/Dividing 50.20 x 1.500 0.412 x 230 1.2x10 8 / 2.4 x 10 -7 50400 / 61321
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Rule for Adding/Subtracting Only place values where all measurements being added/subtracted have sig figs are utilized EX: 1002 + 1.2345 1003
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Practice Adding/Subtracting 100.23 + 56.1.000954 + 5.0542 1.2 x 10 4 – 5.02 x 10 3 1.0045 + 0.0250
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