Standards for MeasurementPowerPoint PresentationSlide 3Slide 4Slide 5Significant Figures (Sig. Figs.)Evaluating ZeroSlide 8Scientific NotationMultiplication or DivisionAddition or SubtractionSlide 12Slide 13Slide 14Système International (SI) The Metric SystemLengthSlide 17Mass Base unit is the kilogram (kg)Slide 19Temperature ConversionDerived UnitsSlide 22Conversion FactorsDimensional AnalysisSimple, One Step ConversionsSlide 26Multiple Conversion FactorsUnits raised to a PowerDensity: Conversion factor mass volumeSolubilitySlide 31Slide 32Standards for MeasurementPreparation for College ChemistryColumbia UniversityDepartment of ChemistryThe Scientific MethodObservationsTheory(Model)HypothesisExperimentLaws(analysis)(analysis)(explanation)(measurement)Measurement and Interpretations1 2 3 4 65 7 8Diameter = 2.5 cmArea =  x r2 = 8.04 cm2Direct MeasurementInterpretation StepArt of Scientific Measurement:• Recognize what can be measured directly.• Devise a way to obtain the desired information from measurement data.Radius = Diameter/2ExperimentationResting Potential = -65 mVUNITNUMERICAL VALUEMeasured DataDerivedBasicAffected by Uncertainty• Accuracy• Precision• Resolution• NoiseSignificant Figures (Sig. Figs.)The mass of an object weighed on a triple beam balance (precision ± 0.1g) is found to be 23.6 g. This quantity contains 3 significant figures, i.e., three experimentally meaningful digits. If the same measurement is made with an analytical balance (precision ± 0.0001g) , the mass might be 23.5820 g (6 sig. fig.)Evaluating ZeroZero is SIGNIFICANT when: Is between nonzero digits: 61.09 has four sig Figs. Appears at the end of a number that includes a decimal point 0.500 has three sig. Figs.; 1000. has four sig. Figs. Zero is NON SIGNIFICANT when: Appears before the first nonzero digit. 0.0025 has two sig. Figs. Leading Zeros are non significant Appears at the end of a number without a decimal point. 1,000 has one sig. Fig.; 590 has two sig. Figs.Exact NumbersDefined numbers, like 12 inches in a foot, 60 minutes in an hour, 1,000mL in one liter. Exact numbers have an infinite number of sig. figs.Exact numbers do not limit the number of sig. figs. in a calculation.Numbers that occur in counting operations.Scientific NotationNumber written as a factor between 1 and 10 multiplied by 10 raised to a power. Useful to unequivocally designate the significant figures.1200 =1.200×10−3 (four digits)6,600,000=6.6×106 (two digits)0.0468 =4.68×10−2 0.00003=3.0×10−5 (two digits)or 3×10−5 (one digit)Multiplication or DivisionThe answer must contain as many significant figures as in the least precise quantity (measurement with least precision).What is the density of a piece of metal weighing 36.123 g with a volume of 13.4 mL?d =massvolume=36.123g13.4mL=2.69575g/mLRound off to 7Drop these three digitsANSWER:2.70g / mLAddition or SubtractionKeep only as many digits after the decimal point as there are in the least precise quantityEx. Add 1.223 g of sugar to 154.5 g of coffee:Total mass = 1.2 g + 154.5 g = 155.7 gAddition or SubtractionNote that the rule for addition and subtraction does not relate to significant figures. The number of significant figures often decreases upon subtraction.Mass beaker + sample = 52.169 g (5 sig. figs.)- Mass empty beaker = 52.120 g (5 sig. figs.)Mass sample = 0.049 g (2 sig figs)Prefix Symbol Value Powerexa E1,000,000,000,000,000,0001018peta P1,000,000,000,000,0001015tera T1,000,000,000,000,1012giga G1,000,000,000109mega M1,000,000106kilo k1,000103hecto h100102deka da10101SI Units Prefixes (Multiples)Prefix Symbol Value Poweratto a0.00000000000000000110-18femto f0.00000000000000110-15pico p0.00000000000110-12nano n0.00000000110-9micro µ0.00000110-6milli m0.00110-3centi c0.0110-2deci d0.110-1SI Units Prefixes (Submultiples)Système International (SI) The Metric SystemPhysical Quantity Name SymbolLength meter mMass kilogram kgTime second sElectric current ampere ATemperature kelvin KAmount of substance mole molLuminous intensity candela cdBased on seven DIMENSIONALLY INDEPENDENT quantitiesLength1790s: 10-millionth of the distance from the equator to the North Pole along a meridian.Base unit is the meter (m)1960-1983: 1,650,763.73 wavelengths of the orange-red emision of 18Kr at standard conditionsSince 1983: 1/299,792,458 of the distance traveled by light in 1 second through vacuum.1889: Distance between two engraved lines on a Platinum-Iridium alloy bar maintained at 0°C in Sevres-France.LengthAtomic dimensions1 km = 103 m 1 in = 2.54cm 1 cm = 10-2 m 1 mile = 1.61km1 mm = 10-3 m1 µm = 10-6 m1 Å = 10-10 m1 nm = 10-9 mEngineering dimensionsMass Base unit is the kilogram (kg)1 kg = 103 g; 1 mg = 10-3 gA mass of 1 kg has a terrestrial weight of 9.8 newtons (2.2 lbs)Depending on the precision required and the amount of material, different balances are used:  The Quadruple Beam Balance (± 10 mg)  The Top Loading Balance (± 1 mg). The Analytical Balance (± 0.1 mg).International prototype: a platinum-iridium cylinder maintained in Sevres-France.Freezing point of waterBoiling point of water10010018032212Fahrenheit1000Celsius273.15373.15KelvinComparison of Temperature ScalesK = °C + 273.15°F = (1.8 x °C ) + 32°C = (°F - 32) / 1.8Temperature ConversionK = °C + 273.15 °F = (1.8 x °C ) + 32 °C = (°F - 32) / 1.8Ex. 2.20 Convert 110°F to °C and K°C = (68° – 32°) / 1.8 = 20°C K = 20 + 273 = 293 KDerived UnitsPhysical quantity Name Symbol DefinitionFrequency Hertz Hz s-1Force newton N m.kg.s-2 Pressure, stress pascal Pa N.m-2 = m-1.kg.s-2 Energy work, heat joule J N.m = m2.kg.s-2 Electric charge coulomb C A.sElectromotive Force volt V J.C-1 = m2.kg.s-3. A-1Electric Resistance ohm  V.A-1 = m2.kg.s-3. A-2Measurement of VolumeConversion Factors€ Unit given×Unit neededUnit given1 in =2,54cm⇒2.54cm1 in or 1 in2.54cmTwo conversion factors€ =Unit neededDimensional Analysis•Read Problem. What needs to be solved for? Write it down•Tabulate data given. Label all factors with proper units•Determine principles involved and unit relationships•Set up the problem deciding for the proper conversion factor•Perform mathematical operations•Check if the answer is reasonableSimple, One Step ConversionsCBS News reported the barometric pressure to be