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MU CHM 141 - Chapter 1

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Chapter 1 Keys to the Study of Chemistry 02/07/20151.1 Fundamental DefinitionsChemistry – study of matter, its composition and properties and the changes it goes through and engergy associated with it.Matter – anything with volume and massVolume – amount of space of object occupies“Weight” = effect of gravityUsually the word weight is used interchangably with mass but chemists usually mean mass when they say weight.Composition – types and amounts of simpler substances that make up matterProperties – observable characteristics used for classificationProperties of Matter…Physical Property – property that shows by itself without interacting with other substancesNo change requiredExample: color, volume, melting/boiling pointChemical Property – properties a substand shows when it does interact with other substancesComposition/identity is changedExample: flammability, corrosiveness, reactions with acidIntensive Properties – independent of the amount of the substadExample: color, melting/boiling point, density, etc.Extensive Properties – dependent on amount of the substandExample: Mass, volume, lengthPractice ProblemLabel each as a:Chemical property or physical propertyExtensive property or intensive propertya. Boiling point of water-Physical/Intensiveb. The mass of a nugget of gold is 25.0 g-Physical/Intensivec. Volume of a nugget of gold is 1.3 cm3-Physical/Extensived. Density of gold is 19.3 g/cm3-Physical/Intensiveratio of mass to volumePhysical Changes: when a substance’s physical propertes change, but composition/identity remains the sameSame substance before and after the changeExample: Solid ice melting into liquid waterChemical Changes: when a substance is converted into a different substance. Its composition/identity changes (chemical reaction)Example: Water decomposes to form hydrogen gas and oxygen gas.States of MatterArrangement of particlesSolidParticles are close and organizedFixed shape/volumeMay be soft, rigid or flexinleLiquidParticles are close together but disorganizedFixed volyme/varying shapeGasFar apart and disorganizedNo fixed shape/volumeTemperature and Change of State- A changed of state is a physical changephysical changes, composition does notreversible by changing temperatureEnergy in ChemistryPhysical and chemical changes are accompanied by energy changesEnergy = ability to do work or transfer heatPotential Energy – energy due to the position or composition of an objectKinetic Energy – energy due to the motion of objectTotal energy = Potential energy + kinetic energyConservation of EnergyEnergy is neither created nor destroyed, only converted from one form to anotherLower energy situation (more stable) are favored oer situation of high energy (less stable)1.2 Chemical Art/Origins of Modern ChemistryFormer BeliefsPhlogiston = substance released when material burnsCalx = when metl burns it form its calx which is heavier than the metalAntione Lavoisier (1743-1794) – french chemistLavoisier’s Experiments and Impacts:Experiment 1: heating mercury calx created mercury and gas which weighed the same as the starting calxSo the calx did not weigh more than the heated metalExperiment 2: heating mercury and with the gas reformed the calx and it still weighed the sameExperiment ¾: heating mercury into calx again and leaving 4/5 of the air to extinguish a a candleLavoisier named the gas oxygen and the metal calxes metal oxides.Explanations:Oxygen combines with a substance when it burnsCombustible substances stop burning once it combines with all the available oxygen (in closed container)Metal calx/metal oxide weighs more than the metal because it contains the mass of the oxygenSummary-Lavoisier marks the beginning of chemical science and overthrows the phlogiston theory by showing quantitatively that oxygen, a component of air, is required for combustion nd combines with a burning substance.1.3 The Scientific Approach: Developing a ModelScientific method: process involving creative propositions and tests aimed at discoveriesObservationsLaw that mass remains the same during chemical change is known as the law of mass conservationHypothesisHypotherses can be altered, but experimental results cannotExperimentModel/theories1.4 Measurements and Chemical Problem SolvingUnit conversion (Dimensional Analysis)Conversion factor = ratio of equivalent quantities used to express a quantity in different unitsExamples:1 yd = 3 ftDivide both sides by 3 ft. Divide both sides by 1 yd.1yd/3ft = 3ft/3ft = 1 1yd/1yd = 3ft/1yd = 1Mutiplying a quantity by a conversion factor is the same as diving by 1.Though the number of and unit change, the size of the quantity remains the same100 yd (3ft/1yd) = 300 ftSample Problem!Dr. Garrity drives 40 miles to Oxford, what is this distance in kilometers?1 mile = 1.609 km40 mi = (1.609 km / 1 mi) = 64.4 km ✓- or -40 mi (1 mi/1.609 km) = 24.9 mi2/km ✕Writing a Conversion FactorDecide which is a larger unit and assign a value of 1.Sample Problem!A marathon runner’s pace is 18.5 ft/sec. What is his pace in feet per minute? What is the pace in miles per hour?a. 1 minute = 60 seconds18.5 ft/sec (60 sec/1 min) = 1,110 ft/minb. 1 mile = 5,280 feet18.5 ft/sec (60 sec/1 min)(60 min/1 hr)(1 mile/5,280 ft) = 12.6 mphUsing a quantity with a derived unit as a conversion factor:can be used as conversion or invertedExample: Price of gas = 3.35$/ga) Cost of 14.5 gallons14.5 gal (3.35$/1 gal) = 48.58$b) How much gas for 20$?20.00S (1 gal/3.35$) = 5.97 gallonsDerived UnitsDensity (mass/volume): you can used one to find the otherMolar Mass (grams/mole): you can use one to find the otherConcentration (mass solute/volume solution)Example: (g solute/L solution)MolaritySample Problem 1.3You need 325 cm of something, it sells for $0.015/ft. How much are you going to pay? *2.54 cm = 1 inch325 cm (1 in/2.54 cm)(1 ft/12 in)($0.15/1 ft) = $1.60Sample Problem 1.6A furniture factory needs 31.5 ft2 of fabric to upholster one chair. Its Dutch supplier sends the fabric in bolts that hold exactly 200 m2. How many chairs can be upholstered with three bolts of fabric? (1 ft = 0.3048 m)1 ft = 0.3048 m1 ft2 = 0.3048 m x 0.3048 m1 ft2 = (0.3048)2m231.5 ft2 = 1 chair3 bolts (200 m2/1 bolt)(1 ft2/(0.3048)2m2)(1 chair/31.5 ft2) = 205 chairsSample Problem 1.7Lithium, a soft, gray solid with the lowest density of any metal, is a key component of advanced batteries. A slab of lithium weighs 1.49 x 103 mg and has sides that are 20.9 mm by 11.1 mm by 11.9 mm.


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