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Chapter 2-1 Method, Measurement & Problem Solving Notesheets Name _________________________ Period _____ Date_______________ I. What is Chemistry? A. Chemistry is the study of all ______________ and the _________________ it can undergo. B. Chemistry has been called the ______________ science because it overlaps so many sciences. C. Chemical – any substance with a __________________ composition. II. The Scientific Method: (2.2) A. A ___________________ approach to gather knowledge. B. Steps to the Scientific Method: 1. _______________________ 2. ________________________ 3. ________________________ 4. ________________________ 5. ________________________ *Note: All hypotheses must be able to be ______________ in order to be a true hypothesis. C. Many Experiments ( Natural Law ) ( Theory ) III. Scientific Notation: Shorthand way of expressing very _____________ or very ___________ numbers. (2.3) A. Power of 10 Equivalent # Reason 100 101 102 103 105 10-1 10-3 10-5 _________ _________ _________ _________ _________ _________ _________ _________ ______________________________ ______________________________ ______________________________ ______________________________ ______________________________ ______________________________ ______________________________ ______________________________ B. Express Numbers in Scientific Notation – move the decimal point so that there is only ____ nonzero digit to the left of the decimal point. Moving the decimal point left the power will be ____, right the power will be ___. 1 1) 2700 ________________ 2) 0.0035 ________________________ 3) 2,640,000,000 ________________ 4) 0.010 ________________________ C. Express Numbers in regular form – reverse the process. 5) 8.65 x 106 ______________________ 6) 9.73 x 10-8 ________________________ D. Know how to use scientific notation in your calculator – different for graphing + scientific! Ex. #7) 8.08 x 10-5 – 2.07 x 10-6 = Ex. #8) 3.7 x 102 Ex. #9) x 5.1 x 103 = 2.3 x 10-3 = 4.6 x 10-7 IV. Metric System: (1.2) A. International System of Measurements (SI): standard system used by all scientists. It is based upon multiples of ______. B. Metric Units used in chemistry: Measurement Equation Derived Unit mass ---------- --------- length ---------- --------- time ---------- --------- temperature ---------- --------- ---------- --------- quantity Unit Instrument -------------------- area volume density -------------------- pressure energy ---------2 C. Prefixes Prefix teragigamegakilohectodekaBASE UNIT decicentimillimicronanopico- Abbreviation Meaning -------------- 1 Scientific Notation D. Metric Conversions using the Factor-Label Method (Dimensional Analysis) Ex. #1) Convert $72 to quarters: 4 quarters 72 dollars 1 dollar Ex. #2) Convert 15 g to kg Ex. #3) Convert 20 mL to kL Ex. #4) Convert 0.071 m3 to Liters Ex. #5) Convert 25 L to m3 Ex. #6) The wavelength of blue light is 450 nm convert to pm 3 V. Uncertainty in Measurement: (2.3) A. Measurements are uncertain because: 1. Instruments are not free from __________________. 2. Measuring always involves some _____________________. B. Estimating with a scale 1. Estimate ______ digit more than the instrument measures 2. is used to show _____________________which is the last ____________________digit. C. Precision: When the instrument gives you about the ____________ results under similar conditions. D. Accuracy: When the experimental value is close to the ____________ value. The____________ the increments of measurement an instrument has, the more accurate it can be. E. An instrument is ________________ (numbers repeatable to a certain number of places) the operator makes it _____________________ (close to the right answer by using it correctly). Ex. Precise, Accurate, Both or Neither (Accepted Value = 15g) 1. 200g, 1g, 40g _____________________________ 2. 78g, 80.g, 79g _____________________________ 3. 16g, 14g, 17g _____________________________ F. Dartboard Analogy: VI. Significant Digits A. Significant Digits include ___________________ digits and ___________________ digits. Use Atlantic-Pacific Rule for determining number of significant digits – see map handout. B. Addition and Subtraction 1. Add or Subtract numbers. 2. Round answer to the least precise piece of equipment (look at __________ places.) Ex. 951.0 g 1407 g 23.911g 158.18 g + 4 B. Multiplication and Division 1. Multiply or Divide numbers. 2. Round answer to the least _________________ of significant digits. Ex. #1) 7.079 cm = 0.535 cm Ex. #2) V = L x W x H V= 3.05 m x 2.10 m x 0.75 m = Ex. #3) A = L x W A= 3200 cm x 2500 cm = VII. Important Formulas: A. Percent Error: Comparing a measurement obtained experimentally with an _________________ value. It is always expressed as a __________________ %. % error = measured value - accepted value x 100% = accepted value Ex.) If a student calculates the density of aluminum to be 2.5 g/cm3, and the accepted value is 2.702 g/cm3, what was her % error? B. Density = Mass Volume M= V= Ex.) If a metal block has a mass of 75.355 g and a volume of 22 cm3, what is the density? Ex.) Determine the volume of 23.249 g of nail polish remover (acetone - density of 0.791 g/mL) 5 VIII. Dimensional Analysis (The Factor-Label Method): A. Uses unit equalities to convert between ________________. A unit equality is an equation that _______________ 2 units. Ex.) 12in = 1 ft 60sec = 1 min 1kg = 1000 g B. Unit equalities are used to write __________________ ________________ which are always equal to “1.” Ex) 1000 m =1 1 km or 1 km =1 1000 m C. The conversion factor is a definition, and therefore infinitely precise, so the number of significant digits in the answer is equal to the number in the ___________which is the _____________ value. Useful Chemistry Conversion Factors 1 in. = 2.54 cm 1 atm = 760 mm Hg 1 ft. = 12 in. 1 atm = 101,325 Pa 1 mile = 5280 ft. 1 cal. = 4.184 J 1 min. = 60 s 1 Cal = 1000 cal 1 hr. = 60 min. 1 gal. = 3.785 L Ex. #1) How many seconds are in 22 hours? Ex. #2) How many years are 3 x 108 seconds? Ex. #3) If there are 9 dibs in 1 sob, 3 sobs in 1 tog, 1 tog in 6 pons, and 12 pons in 1 gob. How many gobs are in 27 dibs? Ex. #4) Calculate the number of feet in a 5.00 km race. (1 inch = 2.54 cm) 6