Using Scientific Measurements - PowerPoint Presentation

1. Using Scientific Measurements

2. Significant FiguresSignificant Figures: Consist of all the digits known with certainty plus one final digit (This digit is estimated by you)The larger markings are labeled every 10 milliliters (mL). In between the larger labeled markings are short marks every 1 mL. The reading for this would be 35.0mL with the .0 being the uncertain #.6.30 cm6.35 cm6.40 cm

3. Reading Measurements for sig FigsWhen reading an Electric Scale there is no need to add on a number. All numbers available are to be used and considered significant.

4. Rules for Determining Sig Figs1) ALL numbers that aren’t zero (1,2,3,4,5,6,7,8,9) are significant. Ex-83765 (5) 2) ALL zeroes between non-zero numbers are significant. Ex- 404 (3) 3) ALL zeroes which are at the end of a number and to the right of the decimal point are significant. Ex-1.5600 (5)4) Zeros appearing in front of all non-zero digits are NOT significant. Ex-0.0012 (2) 10.0090 (6)5)Zeros at the end of a number but to the left of a decimal point are significant only if a decimal point has been placed to the right of that zero. If there is no decimal point then they are NOT significant. Ex-5000 (1) 5000. (4) 750 (2)

5. Rounding RulesFind the number you want to keep and look at the next number: If it is…..Examples:(rounded to 3 sig figs)Greater than 5, increase the last digit by 1.56.87g …..56.9gLess than 5, do not change the last digit.12.02 L ….12.0 LEqual to 5, followed by a number other than zero, increase the last digit by 1.3.7851 s …. 3.79sEqual to 5, followed by nothing or a zero If the number you are keeping is odd, increase the odd digit by 1.2.835 m ….2.84 m (because 3 is odd)Equal to 5, followed by nothing or a zeroIf the number you are keeping is even, do not change the even digit.2.645 mL …. 2.64 mL (because 4 is even)

6. Sig Fig PracticeDetermine the number of Sig Figs4932.20 cm0.0400 L804.5 g0.0144030 km1002 m400 mL30000. cm0.0000625000 kgSuppose the value “seven thousand cm” is reported to you. How would it be expressed if:You wanted to indicate1 Sig FigYou wanted to indicate 4 Sig FigsYou wanted to indicate 6 Sig Figs

7. Significant FiguresAddition and Subtraction RulesThe answer must be rounded so that it contains the same number of digits to the right of the decimal point as there are in the measurement with the smallest number of digits to the right of the decimal point.Ex. 2.89 m + 0.00043 m = 2.89043 m = 2.89 m Multiplication RulesThe product or quotient should be rounded off to the same number of significant figures as in the measurement with the fewest significant figures.Ex. 3.5293 mol x 34.2 g/mol = 120.70206 g = 121 gConversion Factors and Sig Figs: Conversion Factors do not affect the amount of Sig Figs because they are exact. This means there is no error in them.

8. Scientific Notation: A method of writing very large and very small quantities as a number times 10 to a power : M x 10n (Example-1404 = 1.404 x 103)Keep all sig figs unless told otherwise.

9. Scientific Notation Find the decimal 569000.00Move (or jump) the decimal until you have one digit to the left of the decimal 569000.00Count the # of jumps (jumped left # is pos, jumped right # is neg) pos neg 569000.00Rewrite the number with the decimal in the new place and attach x 10 5.69 x 10Add the number of jumps as an exponent on the x 10 5.69 x 105

10. Quantity-Anything that is measurable (has magnitude, size, or amount) ex- length, time, volume, mass…..etc.Measurement-Represents a quantity with a # and unitSI Base Units: The International System of Units 1-Length- l 2-Mass- m meter-m kilogram-kg 3-Time- t 4-Temperature- T 5-Amount of Substance-n seconds-s Kelvin-K mole-mol

11. Converting TemperatureKo= Co + 273.15Fo = 9/5 (Co+32) Co = 5/9(Fo-32)Convert the following to Kelvin 1) 0o C ________2) -50o C ________3) 90o C ________4) -20o C ________ Convert the following to Celsius 5) 100o K ________6) 200o K ________7) 273o K ________8) 350o K ________

12. Units ContinuedDerived Units: Any combination of SI Base UnitsDensity: g/cm3Weight-Measure of the gravitational pull on matter (measured with a Spring Scale)Newtons=kg • m s2

13. Mass Mass is the amount of matter present. How much stuff is there?Mass and weight are not the same thingWhy do they seem the same here on earth?Will a person’s mass change on the moon?Will a person’s weight change on the moon?(m)

14. Volume (V)Volume is a measure of how much space an object takes up.Measure volume in 2 waysSolid straight sided objects-metric: cm3, m3, mm3, etcLxWxH=VolumeLiquids and odd shaped objects: mL, L, kL, cL, etcUse Graduated Cylinder or use water displacement1mL=1cm3

15. Density: The ratio of mass to volumeD=m/VAll substances have a very specific density.Density graphs are Directly ProportionalWhat would have to change to make density vary? GoldDensity=19.32 g/cm3Density= 19.32 g/cm3Memorize: Water has a density of 1g/mL or 1g/cm3

16. Density Practice ProblemsSilver has a density of 10.5 grams/cm3 and gold has a density of 19.3 g/cm3. Which would have the greater mass, 5cm3 of silver or 5cm3 of gold?Gold with 96.5 gAn irregularly shaped stone was lowered into a graduated cylinder holding a volume of water equal to 2 ml. The height of the water rose to 7 ml. If the mass of the stone was 25 g, what was its density?Density=5 g/mL1-Which Sample would be at the top of the column?2-Which sample would fall to the bottom of the column?Density Column

17. Accuracy and Precision Accuracy-The closeness of measurements to the correct or accepted valueHow close was your measured value to the accepted value?Precision-The closeness of a set of measurements of the same quantity made in the same way.How reproducible are your measurements?

18. % Error% Error: This is used to find out how accurate a measurement or average measurement is.(Subtract the accepted value from the measured value, divide by the accepted value) multiply by 100 measured-accepted x 100 = % Error acceptedNegative sign (-) means measured # was smallerPositive sign (+) means measured # was biggerEx. If the accepted Density of cork is .24 g/cm3 and you measured it to be .26 g/cm3 then the % error would be: .26 g/cm3 - .24 g/cm3 x 100 = 8.3% .24 g/cm3

19. Converting between unitsDimensional Analysis: An equation used to solve a problem using units or labels. Also called the factor label method.It is used to go from one unit to another.Conversion Factor: Relationship between the two units.You must ask how much of one does it takes to equal the other?Equation: Starting Amount finishing unit = Finishing Amount starting unitExample of conversion factor for dollars and quarters 4 quarters or 1 dollar 1 dollar 4 quartersExample of conversion factor for cm and m 100cm or 1m 1m 100cmConversion Factor

20. Dimensional AnalysisDraw a T bar (Magic Bridge)Find out the starting amount and unit. Hint**It’s a number with a unit. Write it down in the upper left hand corner.Now decide on the finishing unit.Make 2 fractions out of the starting and finishing units. How much of one equals the other?Pick the fraction that has the starting unit on the bottom and place it into your T bar on the right hand side.Cancel out any units that will cancel.Multiply the stuff on top and divide by the stuff on the bottom.1x10-9 1x10-6 .001 .01 .1 1 10 100 1000 1x106 1x109G M k h da m d c m µ n L g

21. Practice304.90 dimes  nickels293 50 pennies  quarters654 cm3  mL8.90258 x104 Fingers  hands6.29 x 1010 sec hours5.43 x103 hr  weeks45.5 cm  m1.540 kg  µg12.4 dL  hL4.5 x 10-6 m  dm9.21 kg  mg.054 x103 Mm  nm1x10-9 1x10-6 .001 .01 .1 1 10 100 1000 1x106 1x109G M k h da m d c m µ n L g

22. Converting Volume and AreaIf you have a measurement that has a unit with an exponent: for example: m2, cm3You must use the same number of conversion factors as there is in the exponent.Example: for m2 you would need to list the conversion factor twiceExample: for cm3 you would need to list the conversion factor three times

23. Converting Units of Volume310 000 cm3 of concrete in cubic meters6.5 m2 of steel sheet in square centimeters0.035 m3 of chlorine gas in cubic centimeters0.49 cm2 of copper in square millimeters1200 µm2 of acetic acid solution in square decimeters87.5 mm3 of actinium in cubic centimeters250 000 cm2 of polyethylene sheet in hm2

24. ExamplesYour Eupopean Hairdresser wants to cut your hair 8.0 cm shorter. How many inches will he be cutting off? (2.54cm = 1in)The SGC Football team needs another 550cm for a 1st down. How many yards is this?If Jules Vern expressed the title of his famous book, “Twenty Thousand Leagues Under the Sea” in feet, what would the title be? (1mile = 5280ft, 1 League = 3.450miles)A piece of wire is 1.4 m long. How many 1.5 cm pieces can be cut from this wire?You need a room that is at least 1.350 x 10-3 km2 for the Junior/Senior Prom. Your Cafetorium is 133.9ft wide and 67.02 ft long. Is the Cafetorium big enough?