ࡱ> =?<q` bjbjqPqP *,::D    0 48u%p p p p p p p p $$$$$$$$+&h(%p p p p p %p p /% p p p $ p $ rX$T$p d -D z $$ E%0u%$c) c)$c)$ p p p p p p p %% p p p u%p p p p 888 888 D,@ Unit 1 Metric system, significant figures, factor label, accuracy And precision Metric system Length - the meter, which is about three feet. Volume - the liter, one tenth of a meter cubed. Or one cubic decimeter Which is a little over a quart. Mass - the kilogram, is the mass of one liter of water at standard temperature. Prefixes Kilo 1000 Hecto 100 Deka 10 Milli 1/1000 Centi 1/100 Deci 1/10 A kilo-gram is 1000 grams and a milli-gram is 1/1000 of a gram. Significant figures Is a method of keeping track of how well or how poorly something was measured. They are very important in good science. When you measure something the last number you record is always an estimated number. Then when you do calculations using these numbers the calculator Assumes they are exact and spits out a number with many more decimal places Than you really measured. It lies. In good science we dont exaggerate the true. Therefore we use the system of Sig Figs to control the exaggeration. Sig Fig Rules Significant figures are all the numbers you know for sure plus one you are unsure of. (Estimated). All non-zero numbers are significant. Zeroes between two non-zero numbers are significant The (0) is significant Zeroes to the right of a non-zero number and to the left of an understood Decimal are not significant. In the number 2000 with no decimal actually written, the three zeroes are only placeholders to show the magnitude of the number. Zeroes to the right of a decimal and to the left of a non-zero number are Not significant. In .0046 the two zeroes are not significant. They are only place holders. Zeroes to the right of a decimal and to the right of a non-zero number Are significant. In 31.00 the zeroes are significant, because the number was Measured to the hundredth place. Math with Sig Figs When multiplying ,your answer can only have the same number of Sig figs as the least significant factor multiplied. 2.46 x 3.8 = 9.348 which becomes 9.3 2.46 is 3 SIG figs and 3.8 is only 2 sig figs, so you round the answer to two sig figs, which is 9.3. The calculator implies that you measured better than you really did. Same rule applies to division When adding ,you may keep your answer to the last decimal place that You know all the added numbers to. 21.765 3.45 + 2.842 28.057 The calculator assumes the digit after the 5 in 3.45 is a zero. But it could be any thing from 1 to 9, therefore the seven in Thousands place of the answer is bogus. And is only used to Round the final answer to 28.06 4.Subtracting, follow the same rule as addition. Factor label problem solving Your in Europe and need to buy a new belt, your waist is 32 inches, but all the belts are labeled in centimeters. What size do you buy? 32.0 inches x 2.54 centimeters = 81.3 centimeters 1.0 inches Note that the inches in the equation cancel out and you are left with centimeters. .50 cups is how many milliliters? .50 cups x 1 pint x 1 qt x 946 ml = 118.25 ml or 120ml at 2sig figs 2 cups 2 pt 1 qt Again note that cups pints and quarts all cancel out leaving only milliliters. We will do most of our math this way! And you must show the work on paper or you Get no credit, even if the answer is correct! We are developing our communication skills. Accuracy how close you come to an accepted value. Also called percent error Percent error = Observed value - Accepted value Accepted value Or % error = O - A A Precision how reproducible your work is, are you consistent? Trial average deviation 1. 3.40 ( 3.45 = .05 absolute deviation of trial # 1 2. 3.45 ( 3.45 = .00 absolute deviation of trail #2 3. 3.50 ( 3.45 = .05 absolute deviation of trial #3 3 (3.45 3(.033 .033 is the averge deviation for the three trials This tells your boss how good you are when there is no accepted value to work with. CUc( 0 T ` 1@.4STVWjkp{Ydmtbv5WgmuyNqP(MNP j-h*CJ h*CJ hRoot Entry F'D@1Table)WordDocument*,SummaryInformation(,DocumentSummaryInformation84CompObjq  FMicrosoft Office Word Document MSWordDocWord.Document.89q