Presentation on theme: "Welcome to AP Chemistry. What is AP Chemistry? l It is several things l Equivalent of 1 year college inorganic chemistry class l A class that will prepare."— Presentation transcript:
Welcome to AP Chemistry
What is AP Chemistry? l It is several things l Equivalent of 1 year college inorganic chemistry class l A class that will prepare you for a test –May 2 @ 7:45 l Hard work l Now lets work
Significant figures l Meaningful digits in a MEASUREMENT l Exact numbers are counted, have unlimited significant figures l If it is measured or estimated, it has sig figs. l If not it is exact. l All numbers except zero are significant. l Some zeros are, some arent
Which zeroes count? l In between other sig figs does l Before the first number doesnt l After the last number counts iff l it is after the decimal point l the decimal point is written in l 3200 2 sig figs l 3200. 4 sig figs
Doing the math l Multiplication and division, same number of sig figs in answer as the least in the problem l Addition and subtraction, same number of decimal places in answer as least in problem.
More Preliminaries Scientific Method Metric System Uncertainty
Scientific method. l A way of solving problems l Observation- what is seen or measured l Hypothesis- educated guess of why things behave the way they do. (possible explanation) l Experiment- designed to test hypothesis l leads to new observations, l and the cycle goes on
Scientific method. l After many cycles, a broad, generalizable explanation is developed for why things behave the way they do l Theory l Also regular patterns of how things behave the same in different systems emerges l Law l Laws are summaries of observations
Scientific method. l Theories have predictive value. l The true test of a theory is if it can predict new behaviors. l If the prediction is wrong, the theory must be changed. l Theory- why l Law - how
Observations Hypothesis Experiment Law Theory (Model) Prediction Experiment Modify
Metric System l Every measurement has two parts l Number l Scale (unit) l SI system (le Systeme International) based on the metric system l Prefix + base unit l Prefix tells you the power of 10 to multiply by - decimal system -easy conversions
Metric System l Base Units l Mass - kilogram (kg) l Length- meter (m) l Volume – cubic meter (m 3 ) l Time - second (s) l Temperature- Kelvin (K) l Electric current- ampere (amp, A) l Amount of substance- mole (mol)
Prefixes l giga- G 1,000,000,00010 9 l mega - M 1,000,00010 6 l kilo - k 1,00010 3 l deci-d0.1 10 -1 l centi-c0.01 10 -2 l milli-m0.001 10 -3 l micro-m0.000001 10 -6 l nano-n0.000000001 10 -9
Deriving the Liter l Liter is defined as the volume of 1 dm 3 l gram is the mass of 1 cm 3
Mass and Weight l Mass is measure of resistance to change in motion l Weight is force of gravity. l Sometimes used interchangeably l Mass cant change, weight can
Uncertainty l Basis for significant figures l All measurements are uncertain to some degree l Precision- how repeatable l Accuracy- how correct - closeness to true value. l Random error - equal chance of being high or low- addressed by averaging measurements - expected
Uncertainty l Systematic error- same direction each time l Want to avoid this l Better precision implies better accuracy l you can have precision without accuracy l You cant have accuracy without precision
Dimensional Analysis Using the units to solve problems
Dimensional Analysis l Use conversion factors to change the units l Conversion factors = 1 l 1 foot = 12 inches (equivalence statement) l 12 in = 1 = 1 ft. 1 ft. 12 in l 2 conversion factors l multiply by the one that will give you the correct units in your answer.
Examples l 11 yards = 2 rod l 40 rods = 1 furlong l 8 furlongs = 1 mile l The Kentucky Derby race is 1.25 miles. How long is the race in rods, furlongs, meters, and kilometers? l A marathon race is 26 miles, 385 yards. What is this distance in rods, furlongs, meters, and kilometers?
Examples l Science 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? l Warp 1.71 = 5.00 times the speed of light l speed of light = 3.00 x 10 8 m/s l 1 knot = 2000 yd/h exactly
l Apothecaries (druggists) use the following set of measures in the English system: l 20 grains ap = 1 scruple (exact) l 3 scruples = 1 dram ap (exact) l 8 dram ap = 1 oz. ap (exact) l 1 dram ap = 3.888 g l 1 oz. ap = ? oz. troy l What is the mass of 1 scruple in grams? Examples
l The speed of light is 3.00 x 10 8 m/s. How far will a beam of light travel in 1.00 ns?
Temperature and Density
Temperature l A measure of the average kinetic energy l Different temperature scales, all are talking about the same height of mercury. l Derive a equation for converting ºF toºC