PSU CHEM 110 - Measurements and Energy

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Measurements and EnergyMeasurements and EnergyExam 1 Concepts You Should Know:Exam 1 Concepts You Should Know:Scientific MeasurementScientific MeasurementUnit ConversionsUnit Conversions (Exam Format)Uncertainties in Scientific MeasurementDemo: Scientific MeasurementEnergy and ThermodynamicsUnits of EnergyFirst Law of ThermodynamicsExothermic and EndothermicState FunctionsInternal Energy (E)Internal Energy (E)State FunctionsAnother Useful State FunctionWhat You Should KnowMeasurements and EnergyCH110 FA11 SAS 1Prepare for Recitation September 1stALEKS Prep Assignment due August 26thALEKS Objective 1 due August 30thANGEL Quiz 1, September 1stLecture 1: August 22nd(Course Introduction)Lecture 2: August 24thLecture 3: August 26thLecture 4: August 29thRead: Ch. 1; Ch. 2.1 – 2.4; Ch. 5.1 – 5.3; Ch. 6.1 – 6.6Additional Preparation*: BLB 1: 17; Packet 1: 1-5BLB 2: 4,31; Packet 2: 1,2,3BLB 5: 3,25,28;BLB 6: 4,25,27; Packet 6: 1-5*ALEKS work is necessary but not sufficient for exam level preparation! Do not neglect the packet!Reminder: Add/Drop period ends Wednesday, August 31stCH110 FA11 SAS 2By the end of Today’s Lecture you should know:SI units and metric conversionsAccuracy and precisionInternal energy and the First Law of ThermodynamicsState FunctionsKEY QUESTIONS: THE BIG PICTUREMeasurements and EnergyHow can I use dimensional analysis to make chemistry problems easier?How can chemical thermodynamics help me to understand energy?Remember: Energy is stored in molecules. How can we use it?What are the standard units of measure in chemistry?What forces drive chemical reactions and how can a chemist harness them?Ballot for use in class.Exam 1 Concepts You Should Know:CH110 FA11 SAS 3• What do the numbers on the periodic table mean?• How do we name common ions, acids, etc.?Chapter 2: NomenclatureChapter 3: Chemical FormulasChapter 6: Energy, Atoms, Orbitals, and the Origins of the Periodic Table• What is mass percent?• What is a mole? What is molecular weight?• What are the empirical formula and the molecular formula of a compound?• What is the relationship between photons, their wavelength, their frequency, and their energy?• How does all that stuff about photons help chemists to understand the nature of atoms?• What is an orbital? How is it defined?• What is the electron configuration of an atom? How do I represent it?• How do the shape, size, and number of orbitalshelp me to understand the periodic table?Exam 1 Concepts You Should Know:CH110 FA11 SAS 4Chapter 7: Periodic TrendsChapter 8: Bonding and Lewis Structures• What are ionization energy, electron affinity, and electronegativity?• What are the trends in atomic size?• How are the sizes of atoms and ions related?• How do these show up in the periodic table?• What are the three types of bonding?• How do we describe bonding in ionic solids?• How is covalent bonding described in terms of enthalpy, strength, bond order, etc.?• What is a Lewis structure?• What do we learn about a molecule when we see that it has more than one Lewis structure?• How do you use the octet rule and its violations to help predict Lewis structures?Scientific MeasurementCH110 FA11 SAS 51. Metric Measurement: SI Unitsmass:length:time:temperature:energy:2. Important prefixes you must knowmega (M):kilo (k):centi (c):milli (m):micro (μ):nano (n):Scientific MeasurementCH110 FA11 SAS 63. Significant FiguresHow many significant figures are there in each of these numbers?Which has the most?Is it even unambiguous?4. Uncertainties• How sure am I that two numbers are actually different?• If my calculator reports a decimal to eight digits, should I use them all in my answer?854 ⇒0.00854 ⇒85400 ⇒Unit ConversionsCH110 FA11 SAS 7Dimensional analysis and careful unit conversion are critical to success.Ex. 1: A laser emits 488 nm light. What is this wavelength in meters? In centimeters?Unit Conversions (Exam Format)CH110 FA11 SAS 8An unknown liquid has a density of 2.14 g/mL. How many mL would a 6.42 g sample of this liquid occupy?A) 3.00x10-3mLB) 2.14 mLC) 3.00 mLD) 6.42 mLE) 2.14x103mLUncertainties inScientific MeasurementCH110 FA11 SAS 9• How do scientists learn about the world? • How certain can we be that a given measurement yields the correct answer?Precision :Accuracy :Measurements are not perfectWhat were the results from our in class measurement?Were the measurements accurate?Were the measurements precise?Demo: Scientific MeasurementDr. Showalter’s HeightNumber of Guesses5’ 5’5’’ 5’10’’ 6’3’’10CH110 FA11 SASEnergy and ThermodynamicsCH110 FA11 SAS 11kinetic energy potential energymechanical 1/2mv2 mass in a place where force can actelectrical moving charge Q1Q2/d(electrostatic)light photonschemical bondssound molecules moving uniformlynuclear binding energyheat molecules moving randomlygravitational mghwhere g = 9.8 m/s2Thermodynamics :Thermochemistry:Units of EnergyCH110 FA11 SAS 12• SI unit: Joule (J)[KE of a 2 kg object moving at 1 m per second using 1/2 mv2, or PE of 100 g at height = 1 m using mgh]In chemistry (!!!)kilojoule 1 kJ =calorie 1 cal =Calorie (dietary) 1 Cal =First Law of ThermodynamicsCH110 FA11 SAS 13• all energy lost by a _______ under observation must be gained by the ___________ (and vice versa)*during energyconversion, some heat is alwaysproduced“Law of conservation of energy”Exothermic and EndothermicCH110 FA11 SAS 14ExothermicenergySystem → Surroundings ∆E =EndothermicenergySurroundings → System ∆E =State FunctionsCH110 FA11 SAS 15State Function:∆ elevationAB• Is Δ elevation a state function ? • Is distance traveled a state function? _____• Is time to bottom a state function? _____Internal Energy (E)CH110 FA11 SAS 16Quantitative definition:E is a state function… Internal Energy (E) :∆E = Efinal– Einitial∆E = +Internal Energy (E)CH110 FA11 SAS 17A macroscopic analogy: Water in a lake.∆E = Efinal– Einitial∆E = q + wE is a state function… Internal energy: How much energy does a chemical possess? How is it stored? How can we use it?State FunctionsCH110 FA11 SAS 18• Are q and w state functions? ____• Is ∆E (= q + w) a state function? ______• State functions are represented by capital letters: reactantsproducts12∆EAnother Useful State FunctionCH110 FA11 SAS 19Enthalpy (∆H)∆H = qpDefined as Energy transferred when P is constant(think of our lake example with dams blocking


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PSU CHEM 110 - Measurements and Energy

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