Topic1:Stoichiometricrelationships13.5hours

Essential idea:Physicaland chemicalpropertiesdepend on the ways in which different atoms combine.

1.1 Introductionto theparticulate nature of matter andchemical change
Nature ofscience:
Making quantitative measurementswith replicatesto ensure reliability—definite and multiple proportions. (3.1)
Understandings:
•Atomsofdifferent elements combine in fixed ratiostoformcompounds, which have different propertiesfromtheircomponent elements.
•Mixtures contain more than one element and/orcompound that are not chemicallybonded togetherand so retain theirindividualproperties.
•Mixturesare eitherhomogeneousorheterogeneous.
Applications andskills:
•Deduction of chemicalequationswhen reactantsand productsare specified.
•Application ofthe state symbols(s), (l), (g)and (aq)in equations.
•Explanation ofobservable changes in physicalpropertiesand temperature during changesofstate.
Guidance:
•Balancing ofequations should include a varietyoftypesofreactions.
•Namesofthe changesofstate—melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and deposition—should be covered. / International-mindedness:
•Chemical symbolsand equationsare international, enabling effective communication amongst scientistswithout needfortranslation.
•IUPAC (InternationalUnion ofPure and Applied Chemistry)isthe world authorityin developing standardized nomenclature forboth organicand inorganic compounds.
Theoryofknowledge:
•Chemicalequationsare the “language”ofchemistry. How doesthe use of universal languageshelp and hinderthe pursuit of knowledge?
•Lavoisier’sdiscoveryofoxygen, which overturned the phlogiston theoryof combustion, isan example ofa paradigmshift. How doesscientific knowledge progress?
Utilization:
•Refrigeration and how it isrelated to the changesofstate.
•Atomeconomy.
•Freeze-drying of foods.
1.1Introductiontotheparticulatenatureofmatterandchemicalchange
•Theterm“latentheat”isnotrequired.
•Namesandsymbolsofelementsareinthedatabookletinsection5. / Syllabusandcross-curricularlinks:
Topic4.1—deductionofformulaeofioniccompounds
Topic5.1—enthalpycyclereaction;standardstateofanelementorcompoundTopic6.1—kinetictheory
Topic8.2—neutralizationreactionsTopic10.2—combustionreactionsOptionA.4—liquidcrystals
Aims:
•Aim8:Thenegativeenvironmentalimpactsofrefrigerationandairconditioningsystemsaresignificant.TheuseofCFCsasrefrigerantshasbeenamajorcontributortoozonedepletion.

Essential idea:Themole makes it possible to correlate the numberofparticleswith the massthat can be measured.

1.2 The mole concept
Nature ofscience:
Concepts—the concept ofthe mole developed fromtherelated concept of“equivalent mass”in the early19th century. (2.3)
Understandings:
•The mole isa fixed numberofparticlesand refersto the amount, n, of substance.
•Massesofatomsare compared ona scale relativeto 12Candare expressed asrelative atomicmass(Ar)and relativeformula/molecularmass (Mr).
•Molarmass(M)hasthe unitsg mol-1.
•The empiricalformula and molecularformula ofa compound give the simplest ratio and the actualnumberofatomspresent in a molecule respectively.
Applications andskills:
•Calculation ofthe molarmassesofatoms, ions, moleculesand formula units.
•Solution ofproblems involving the relationshipsbetween the numberof particles, the amount ofsubstance in molesand the mass in grams.
•Interconversion ofthe percentage composition bymassand the empirical formula.
•Determination ofthe molecularformula ofa compound fromitsempirical formula and molarmass.
•Obtaining and using experimentaldata forderiving empiricalformulasfrom reactions involving mass changes. / International-mindedness:
•The SI system(Système Internationald’Unités) refersto the metric systemof measurement, based on seven base units.
•The InternationalBureau ofWeightsand Measures(BIPMaccording to its French initials)isan international standardsorganization, which aimsto ensure uniformityin the application ofSI unitsaround the world.
Theoryofknowledge:
•The magnitude ofAvogadro’s constantisbeyond the scale ofoureveryday experience. How doesoureverydayexperience limit our intuition?
Utilization:
•Stoichiometric calculationsare fundamentalto chemicalprocessesin research and industry, forexample in the food, medical, pharmaceuticaland manufacturing industries.
•The molarvolume forcrystalline solidsisdetermined bythe technique ofX- raycrystallography.
Syllabusand cross-curricularlinks:
Topic2.1—the scale ofatomsand theircomponent particles
Topics4.1, 4.3 and 4.5—lattice structure of ionic compounds, molecularstructure ofcovalentcompoundsand metallic lattice
Topics5.1 and 15.2—standard enthalpyand entropychangesdefined permole Topic19.1—mole ratiosofproducts in electrolysis
1.2Themoleconcept
Guidance:
•ThevalueoftheAvogadro’sconstant(LorNA)isgiveninthedatabookletinsection2andwillbegivenforpaper1questions.
•Thegenerallyusedunitofmolarmass(g mol-1)isaderivedSIunit. / Aims:
•Aim6:Experimentscouldincludepercentmassofhydrates,burningofmagnesiumorcalculatingAvogadro’snumber.
•Aim7:Dataloggerscanbeusedtomeasuremasschangesduringreactions.

Essential idea:Mole ratios in chemicalequationscan be used to calculate reacting ratiosbymassand gasvolume.

1.3 Reactingmasses andvolumes
Nature ofscience:
Making carefulobservationsand obtaining evidenceforscientifictheories—Avogadro's initialhypothesis.(1.8)
Understandings:
•Reactants can be eitherlimiting orexcess.
•The experimentalyield can be differentfromthe theoreticalyield.
•Avogadro’s law enablesthe mole ratio ofreacting gasesto be determined from volumesofthe gases.
•The molarvolume ofan idealgas isaconstant at specified temperature and pressure.
•The molarconcentration ofa solutionisdetermined bythe amount ofsolute and the volume ofsolution.
•A standard solutionisone of known concentration.
Applications andskills:
•Solution ofproblemsrelatingto reacting quantities,limiting and excess reactants, theoretical, experimentaland percentage yields.
•Calculation ofreacting volumesofgasesusing Avogadro’s law.
•Solution ofproblemsand analysisofgraphs involving therelationship between temperature, pressure and volume fora fixed massofan idealgas.
•Solution ofproblemsrelatingto the idealgasequation.
•Explanation ofthe deviationofrealgasesfromidealbehaviourat low / International-mindedness:
•The SI unit ofpressure isthePascal(Pa),N m-2, but many otherunitsremain in common usage in different countries. These include atmosphere (atm), millimetresofmercury (mm Hg), Torr, barand poundspersquare inch (psi). The bar (105Pa)isnow widelyused asa convenient unit,as it isverycloseto 1 atm. The SI unit forvolumeism3, although litre isa commonlyused unit.
Theoryofknowledge:
•Assigning numbersto the massesofthechemicalelementshasallowed chemistryto develop into a physicalscience.Whyismathematics so effective in describing the naturalworld?
•The idealgasequation can be deduced froma smallnumberofassumptions ofidealbehaviour.Whatisthe role ofreason, perception,intuition and imagination in the development ofscientificmodels?
Utilization:
•Gasvolume changesduringchemicalreactionsare responsibleforthe inflation ofairbagsin vehiclesand are the basisofmanyotherexplosive reactions, such asthe decomposition ofTNT (trinitrotoluene).
•The concept ofpercentage yield isvitalin monitoring the efficiencyof industrialprocesses.
Syllabusand cross-curricularlinks: Topic4.4—intermolecularforces
Topic5.1—calculationsofmolarenthalpychanges
1.3 Reactingmasses andvolumes
temperature and high pressure.
•Obtaining and using experimentalvaluesto calculate the molarmassofa gas fromthe idealgasequation.
•Solution ofproblems involving molarconcentration, amount ofsolute and volume ofsolution.
•Use ofthe experimentalmethod oftitration tocalculate the concentration ofa solution by reference to a standard solution.
Guidance:
•Valuesforthe molarvolumeofan idealgasare given in the data booklet in section 2.
•The idealgasequation,????=?????�, and the value ofthe gas constant (R)are
given in the data booklet in sections1 and 2.
•Unitsofconcentrationtoinclude:g dm-3,moldm-3andpartsper million (ppm).
•The use ofsquare bracketsto denote molarconcentration isrequired. / Topic9.1—redoxtitrations
Topic17.1—equilibriumcalculations Topic18.2—acid-base titrations
Topic21.1 and A.8—X-raycrystallography Physicstopic3.2—Idealgaslaw
Aims:
•Aim6: Experimentaldesign could include excessandlimiting reactants.
Experiments could include gravimetricdetermination byprecipitation ofan
insoluble salt.
•Aim7: Data loggers can be used to measure temperature, pressure and volume changes in reactionsorto determine the value ofthe gas constant, R.
•Aim8: The unit partspermillion, ppm, is commonlyused in measuring small levelsofpollutants influids.Thisunit is convenientforcommunicating very low concentrations, butisnota formalSI unit.

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