1. Copy down HW 2. Take out HW & COMPARE your work to your table partner’s

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BELLWORK. 1. Copy down HW 2. Take out HW & COMPARE your work to your table partners. Chemical Reactions & Equations. Chemical Equations. Shows what takes place during a chemical reaction Reactant : (substances reacting) on left Arrow - ( ) at center ; yields or produces - PowerPoint PPT Presentation

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  • S.BarryChemical EquationsA + B C + DREACTANTSPRODUCTS Shows what takes place during a chemical reactionReactant : (substances reacting) on leftArrow - () at center ; yields or producesProducts: (new substances formed) on right

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  • S.BarryCoefficients: how many? ; # appears in FRONT of the formula molecules for covalent substances moles of atomsunits for ionic substances3CO2 2Mg 4MgO 3 molecules of carbon dioxide2 moles of magnesium4 units of magnesium oxidePhases: solid (s), liquid (l), gas (g), Aqueous (aq)

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  • S.BarryWriting EquationsNames of reactants: methane & oxygenNames of products: carbon dioxide & waterCH4 + 2O2 CO2 + 2H2O How many of each (coefficient): __CH4 ____O2 ____CO2 ___H2O

    Ratio of coefficients: ___: ____: ___: ___

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  • S.BarryExpressing Chemical EquationsWord: carbon + oxygen yields carbon dioxide Remember your diatomic gases: (BrINClHOF)Formula: C + O2 CO2+Diagram:

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  • S.BarryExpressing Equations with wordsto produce How many? Of what? In what state?Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)One atom of solid zincreacts withtwo molecules of aqueous hydrochloric acidone unitof aqueous zinc chlorideand onemolecule of hydrogen gas.

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  • S.BarryExothermic & Endothermic Processes see RB pg 34 table 2.5Exothermic: release energy; surrounding temp increasesA + B AB + energyCH4 + 3 O2 CO2 + 2 H2O + energyEndothermic: require/absorb energy; surrounding temp decreasesAB + energy A + B H2O(s) + energy H2O (l)

    Endothermic video http://www.youtube.com/watch?v=5RJLvQXce4A

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  • S.BarryLaw of Conservation of Mass/Matter/EnergyMatter is neither created nor destroyed in chemical reactions. In any chemical total numbers & kinds of atoms must remain unchanged in the reaction. This is called a balanced equation.

    Charge, energy, mass, and # atoms are conserved (unchanged) in balanced reactions

    4 H2 O4 H2 O4 g32 g36 g

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  • S.BarrySigns of a Chemical ReactionEvolution of heat and lightFormation of a gasFormation of a precipitateColor change

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  • S.BarryChemical Change chemical composition changesSigns of a Chemical ReactionEvolution of heat and lightFormation of a gasFormation of a precipitateColor change

    Physical Change chemical composition remains the sameExamples of a physical changeRipping, tearing, breakingBoiling, melting, freezing, vaporing a substance (a phase change)dissolvingExamples of a chemical changeBurning, rusting, oxidizingFlammable, explosive, reacting

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    IIIIIIIVV

    S.BarryII. Balancing Equations

    Chemical Reactions

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  • S.BarryA. Balancing Steps1.Write the unbalanced equation.2.Count atoms on each side.3.Add coefficients to make #s equal.Coefficient subscript = # of atoms4.Reduce coefficients to lowest possible ratio, if necessary.5.Double check atom balance!!!

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  • S.BarryB. Helpful TipsBalance one element at a time.Update ALL atom counts after adding a coefficient.If an element appears more than once per side, balance it last.Balance polyatomic ions as single units.1 SO4 instead of 1 S and 4 O

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  • S.Barry1 11 12 32 3 6 333 2C. Balancing ExampleAluminum and copper(II) chloride react to form copper and aluminum chloride. 2 2

    6

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    IIIIIIIVV

    S.BarryChemical ReactionsIII. Types of Chemical Reactions

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  • S.BarryA. CombustionCH4(g) + 2O2(g) CO2(g) + 2H2O(g)the burning of any substance in O2 to produce heatA + O2 B

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  • S.Barry Na(s)+ O2(g) C3H8(g)+ O2(g) 5 3 4A. CombustionProducts:contain oxygenhydrocarbons form CO2 + H2O CO2(g)+ H2O(g) Na2O(s) 4 2

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  • S.BarryB. Synthesisthe combination of 2 or more substances to form a compoundonly one productA + B AB

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  • S.BarryB. SynthesisH2(g) + Cl2(g) 2 HCl(g)

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  • S.Barry Al(s)+ Cl2(g) AlCl3(s)2 3 2B. SynthesisProducts:ionic - cancel charges

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  • S.BarryC. Decompositiona compound breaks down into 2 or more simpler substancesonly one reactantAB A + B

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  • S.BarryC. Decomposition2 H2O(l) 2 H2(g) + O2(g)

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  • S.Barry KBr(l) K(s) + Br2(l) 2 2C. DecompositionProducts:binary - break into elements

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  • S.BarryD. Single Replacementone element replaces another in a compoundmetal replaces metal (+)nonmetal replaces nonmetal (-)A + BC B + AC

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  • S.BarryD. Single ReplacementCu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)

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  • S.Barry Fe(s)+ CuSO4(aq) Cu(s)+ FeSO4(aq)D. Single ReplacementProducts:metal metal (+)nonmetal nonmetal (-)free element must be more active (check activity series-Table J) Br2(l)+ NaCl(aq) N.R.

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  • S.BarryAB + CD AD + CBE. Double Replacementions in two compounds change partnerscation of one compound combines with anion of the other

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  • S.BarryE. Double ReplacementPb(NO3)2(aq) + K2CrO4(aq) PbCrO4(s) + 2KNO3(aq)

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  • S.BarryPb(NO3)2(aq)+ KI(aq) PbI2(s)+ KNO3(aq)E. Double ReplacementProducts:switch negative ionsone product must be insoluble (check solubility table) NaNO3(aq)+ KI(aq) N.R. 2 2

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