2Conversions Quantity English unit abb SI unit Definition massPoundsounceslbs ozgramgamount of matter in an objectvolumeGallonquartgal qtliterLamount of space an object occupieslengthInches, feetYards, milesin ft yd mimetermdistance between two objectstimesecondsHrSminSecondssfinite durationtemperatureFahrenheitºFKelvinCelsiusKºChow hot or cold something isamount ofsubstanceN/Amolemolthe amount of a substance
3Based on the Power of 10 106 M 109 G 1012 T micro 10-6 μ nano 10-9 n KingHenryDiedBydrinkingchocolatemilkKiloHectaDecabasedecicentimilli10001001010.10.010.00110^310^210^110^010^-110^-210^-3MEGA106Mmicro10-6μGIGA109Gnano10-9nTERA1012Tpico10-12p
6Accuracy v. PrecisionAccuracy- How close a measured value agrees w/ the correct valuePrecision-How close ea. Measurement agrees w/ ea. other
7Which of the measuring devices would provide a more accurate measurement?Why is this onea better deviceto use for measuring?Sec 2-3Pg 44-57
8Sig Figs(a) Exact Numbers: may be counted or defined. Are absolutely accuratePeople in a room.There is some uncertainty in measurements.Sig. Figs. Indicate the uncertainty in the measurements.Digits believed to be correct by those that makes themCan only report ONE estimated digit.
9Using Scientific Measurements Using a calibrated instrument of measure you can be certain of the accuracy of some of the digits measured.The last digit of the measurement is however, always questionableExcluding the last digit would be misleadingWith the last digit you have some indication of the value’s likely rangeAny measurement reported should consist of the certain digits plus the uncertain digit.The last digit is uncertain, but it isn’t insignificant…
11Using Scientific Measurements Since only the significant digits are reported it is important to be able to determine all the significant digits in a measurement.There are a set of rules that allow us to determine the significance of any figures in any measurement even if we don’t know the origin of the measurement
12RULES FOR SIG FIGSZeros (0) used only to position the decimal are not significant. 3 sig figs23000 depends on the measurement
13RULES FOR SIG FIGS Correct answer =15.2 cm2 2. In x/÷, an answer contains no more sig figs than the least # of sig figs used in the operation.ie: (12.34 cm)*(1.23 cm) = cm2Correct answer =15.2 cm2
14RULES FOR SIG FIGS (37.24+10.3)=47.5447.5 (27.87-21.2342)=6.63586.64 In +/- the last digit retained in the answer is determined by the position of the first estimated number.In other words( )=47.5447.5( )=6.63586.64
15Measurements: Sig Figs Only measurements are given significance.There are some numbers that aren’t considered in terms of significance.Conversion factors have an infinite number of significant figures (ratios of equal measures, like 1 ft/12 in or 60 sec/1 min)Exact numbers also have an infinite number of significant figures, like 20 apples or 10 test tubesSec 2-3
16Your Turn…How many significant figures does each of the following measurements have?29.0 km11000 g3505 btu2sec41.040 ampskg6
17Measurements: Sig Figs Just because the calculated answer in your calculator has 8 digits in the answer – doesn’t mean they are all significantAnswers calculated from measurements may not be expressed with more significant digits than any of the original measure mentsCalculator answers must be rounded to reflect the least accurate measurementSec 2-3Pg 44-57
18Carry out each of the mathematical operation. Your Turn…Carry out each of the mathematical operation.Calculate the area of a crystal surface that measures 1.34 m by m.Calculate how many minutes a project took if the times spent on it each day were 92.5 min, min, 25.0 min, 45 min, and min.Calculate how many hours the result from #2 would work out to be.1.00 m, 291 min, 4.85 hrs
19Your Turn…Write the following #’s in sci notation…3.27 x 10432,7001.024 x 1061,024,000x 10-3
20Scientific On the Notation Calculator Sec 2-3 Pg 44-57 4.587E4/1.2E-3 On theCalculator█2nd function button you push before the EE buttonAvoid this button like the plagueThe EE button is 2nd function of the comma buttonUse this button to enter a negative numberSec 2-3Pg 44-57
21Derived UnitsUnits that are made up of 2+ basic units, ie. Velocity, force, acceleration.DensityAmount of mass per unit volume.D=m/vUnites are g/cm3 or g/mL or g/LCm3 is a unit of volume for solids because v=l*w*h cm*cm*cm=cm3Example: A mL sample of ethanol has a mass of 37.32g. What is its density? (hint: denisty= mass/volume)
22Derived Units Specific Gravity Ratio of a substance’s density to the density of H2ODensity of degrees CNo units
23How to: Derived Units Read problems Write formula Write variables Plug in numbersSolveFor example: Express the density of mercury in lb/ft3 if the density if g/cm3.
24Your Turn…A block of Zinc metal has the dimensions 5.0 cm X 7.0 cm X 20.0 cm, and its mass is 5.0 kg. What is the density of the Zinc metal in g/mL? Zinc’s density is 7.13 g/cm3, what is the percent error from the lab?
25Dimensional Analysis Also called the factor label method Easy way to convert between English and SI (metric).Uses equivalent amounts12 in = 1 ft = 12in/1ft38m=______________ft.
26More conversions length volume mass English to Metric Conversions length2.54cm=1in39.37in=1m1.609km=1mivolume1L=1.057qt28.32L=1cubic footmass453.6g=1lb1g= oz1 metric ton=1.102 standard tonnes
28Dimensional Analysis Answers 29in or 2.9*101in5.1tsp1*102lbs9.94*101mi9.5*10-1gal1.76*104oz1.09*102ydsExample 2: 8.484*102lbs/ft3
29% Error%Error = (Actual-Theoretical) ___________________ * 100 Theoretical Will be Θ if the accepted value is greater. (+) if the accepted value is less.
30Problems Express 12gal in cm3. Suppose Mrs. Fraga’s Bentley contains a gas tank (handmade) that holds up to 16 gal of fuel. The price of gas is $0.315 per Liter (obviously not a problem). How much would Mrs. Fraga need to charge on her AmEx Platinum for one full tank of gas? Does not include tip.