Significant Figures and Scientific Notation HW: read Chapter 5

 KiloHectoDekaBASEdecicenti milli  (King Henry Died By Drinking Chocolate Milk) Quick Metric Conversion Review

Metric Conversion Practice  A) 3.5 DaL = _____ mL  B) 87 Hm = _____ Km  C) 0.61 cL = _____ L  D) 29.5 kg = _____ dg

Temperature Conversions Celsius, Fahrenheit, Kelvin

 YOU TRY!  A) 212 o F = _____ o C?  B) 25 o C = _____ K  C) 37 o C = _____ o F Temperature Conversions

Accuracy and Precision 7 Accuracy: how close a measurement is to its correct value Precision: how closely individual measurements agree with one another

 Percent error is the difference between the measured value and the exact/known value; and given as a percent |accepted value – experimental value| x 100 % accepted value  Example: You are given aluminum and you measure the dimensions of the block and its displacement in a container. You calculate the density of the Al to be 2.67 g/cm3. You look up the density of the Al and find it to actually be 2.70 g/cm3. Calculate the % error of your measurement. Percent Error

 Write a very large number in scientific notation by moving the decimal point to the left until only one digit remains to the left. The number of moves of the decimal point gives you the exponent.  Examples:  3,454,000 = x 10 6  1,200 = 1.2 x 10 3 Scientific Notation

 For very small numbers, you move the decimal point to the right until only one digit remains to the left of the decimal point. The number of moves to the right gives you a negative exponent:  Example:  = 5.43 x 10 7  = 9.2 x 10 3 Scientific Notation

 YOU TRY! Write the following in scientific notation.  A) 908,000,000,000 =  B) =  C) =  D)135,700 =

 1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant.  2) ALL zeroes between non-zero numbers are ALWAYS significant.  3) ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant.  4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant. Sig Fig Rules

 A)  B)  C)  D)780  E)780. How many sig figs??

 F)  G)8.10  H)300,000  I)  J)24.07 More practice???

 In mathematical operations involving significant figures, the answer is reported in such a way that it reflects the reliability of the least precise operation. Math with sig figs

 Addition/Subtraction: (look at decimal place)  1) Count the number of sig figs in the decimal portion of each number in the problem.  2) Add or subtract in the normal fashion.  3) Round the answer to the LEAST number of places in the decimal portion of any number in the problem.  Multiplication/Division (look at sig figs)  1) Count the number of sig figs  2) The LEAST number of sig determines the number of sig figs in the answer Math with sig figs

 A) =  B) =  C)64.61 x 0.5 =  D)200 / 7.65 =  E)( x 10 7 ) ÷ (5.61 x 10¯ 4 ) = Math Computation Examples

 A) How many seconds are in a day?  B) If you are going 50 miles per hour, how many feet per second are you traveling?  C) Your car's gas tank holds 18.6 gallons and is one quarter full. Your car gets 16 miles/gal. You see a sign saying, "Next gas 73 miles." Do you have enough gas? Dimensional Analysis