2 What is AP Chemistry? It is several things Equivalent of 1 year college inorganic chemistry classA class that will prepare you for a testMay 7:45Hard workNow let’s work
3 Significant figures Meaningful digits in a MEASUREMENT Exact numbers are counted, have unlimited significant figuresIf it is measured or estimated, it has sig figs.If not it is exact.All numbers except zero are significant.Some zeros are, some aren’t
4 Which zeroes count? In between other sig figs does Before the first number doesn’tAfter the last number counts iffit is after the decimal pointthe decimal point is written insig figssig figs
5 Doing the mathMultiplication and division, same number of sig figs in answer as the least in the problemAddition and subtraction, same number of decimal places in answer as least in problem.
6 Scientific Method Metric System Uncertainty More PreliminariesScientific MethodMetric SystemUncertainty
7 Scientific method. A way of solving problems Observation- what is seen or measuredHypothesis- educated guess of why things behave the way they do. (possible explanation)Experiment- designed to test hypothesisleads to new observations,and the cycle goes on
8 Scientific method.After many cycles, a broad, generalizable explanation is developed for why things behave the way they doTheoryAlso regular patterns of how things behave the same in different systems emergesLawLaws are summaries of observations
9 Scientific method. Theories have predictive value. The true test of a theory is if it can predict new behaviors.If the prediction is wrong, the theory must be changed.Theory- whyLaw - how
10 Law Observations Theory (Model) Hypothesis Modify Experiment PredictionLawExperiment
11 Metric System Every measurement has two parts Number Scale (unit) SI system (le Systeme International) based on the metric systemPrefix + base unitPrefix tells you the power of 10 to multiply by - decimal system -easy conversions
12 Metric System Base Units Mass - kilogram (kg) Length- meter (m) Volume – cubic meter (m3)Time - second (s)Temperature- Kelvin (K)Electric current- ampere (amp, A)Amount of substance- mole (mol)
13 Prefixes giga- G 1,000,000,000 109 mega - M 1,000,000 106 kilo - k 1,deci- dcenti- cmilli- mmicro- mnano- n
14 Deriving the Liter gram is the mass of 1 cm3 Liter is defined as the volume of 1 dm3gram is the mass of 1 cm3
15 Mass and Weight Mass is measure of resistance to change in motion Weight is force of gravity.Sometimes used interchangeablyMass can’t change, weight can
16 Uncertainty Basis for significant figures All measurements are uncertain to some degreePrecision- how repeatableAccuracy- how correct - closeness to true value.Random error - equal chance of being high or low- addressed by averaging measurements - expected
17 Uncertainty Systematic error- same direction each time Want to avoid thisBetter precision implies better accuracyyou can have precision without accuracyYou can’t have accuracy without precision
18 Using the units to solve problems Dimensional AnalysisUsing the units to solve problems
19 Dimensional Analysis Use conversion factors to change the units 1 foot = 12 inches (equivalence statement)12 in = = 1 ft ft in2 conversion factorsmultiply by the one that will give you the correct units in your answer.
20 Examples 11 yards = 2 rod 40 rods = 1 furlong 8 furlongs = 1 mile The Kentucky Derby race is 1.25 miles. How long is the race in rods, furlongs, meters, and kilometers?A marathon race is 26 miles, 385 yards. What is this distance in rods, furlongs, meters, and kilometers?
21 ExamplesScience fiction often uses nautical analogies to describe space travel. If the starship U.S.S. Enterprise is traveling at warp factor 1.71, what is its speed in knots?Warp 1.71 = 5.00 times the speed of lightspeed of light = 3.00 x 108 m/s1 knot = 2000 yd/h exactly
22 ExamplesApothecaries (druggists) use the following set of measures in the English system:20 grains ap = 1 scruple (exact)3 scruples = 1 dram ap (exact)8 dram ap = 1 oz. ap (exact)1 dram ap = g1 oz. ap = ? oz. troyWhat is the mass of 1 scruple in grams?
23 ExamplesThe speed of light is 3.00 x 108 m/s. How far will a beam of light travel in 1.00 ns?