2 Evidence of Chemical Reactions Chemical Reaction: The process by which the atoms of one or more substances are rearranged to form different substances.Temperature changeColor changeGas or solid appears
3 Representing Chemical Reactions SymbolMeaning+Separates two or more products or reactants→Separates reactants from products(s)Solid State(l)Liquid State(g)Gaseous State(aq)Identifies water solutionChemical EquationReactants: substances reacting; on left sideProducts: substances produced; on right side
4 Representing Chemical Reactions How would you write an equation for sodium reacting with chloride to make sodium chloride?Reactant 1 + Reactant 2 → Product 1sodium + chloride → sodium chlorideNa (s) + Cl2 (g) → NaCl (s)
5 Representing Chemical Reactions Law of Conservation of Mass: atoms cannot be created or destroyed.All atoms in reactants must be in products, and visa versaBalancing the equationNa (s) + Cl2 (g) → NaCl (s)Can not occur without coefficients: number written in front
6 Balancing Equations Write Equation Count atoms in of elements in reactantsCount atoms of elements in productsChange the coefficients to make # of atoms equalWrite coefficients in their lowest ratioCheck
7 Balancing Equations Na (s) + Cl2 (g) → NaCl (s) H2 (g) + O2 (g) → H2O (l)AgNO3(aq) + Cu(s) → CuNO3(aq) + AgAl(s) + O2(s) → Al2O3
8 Classifying Chemical Reactions 5 typesNeed to be able to recognize different types.Need to be able to predict products of different types of reactions
9 Synthesis ReactionsA chemical reaction in which two or more substances react to produce a single product.A + B → ABNa (s) + Cl2 (g) → NaCl (s)Compounds combining is also synthesisCaO(s) + H2O(l) → Ca(OH)2
10 Combustion ReactionOxygen combines with a substance to produce heat and energy2H2(g) + O2(g) → 2H2O(g)All combustion are synthesis not all synthesis are combustion.
11 Combustion Reaction CH4, methane, is a hydrocarbon hydrocarbon + oxygen → carbon dioxide + waterCH4(g) + 2O2(g) → CO2(g) + 2H2O(g)Can be tough to balance, always balance O2 last.
12 Decomposition Reactions Single compound breaks down into two or more elements or compounds.AB → A + BOften requires an energy source.NH4NO3(s) → N2O(g) + 2H2O(g)Air Bags2NaN3(s) → 2Na(s) + 3N2(g)
13 Single Replacement Reactions A reaction in which the atoms of one element replace the atoms of anotherA + BX → AX + BCu(s) + 2AgNO3(aq) → 2Ag(s) + Cu(NO3)2(aq)
14 Double Replacement Reactions Exchange of ions between two compoundsAX + BY → AY + BXCa(OH)2 (aq) + 2HCl (aq) → CaCl2 (aq) + 2 H2O(l)All double replacement reactions produce either a precipitate, a gas, or water
15 Double Replacement Reactions Precipitate: a solid being produced during a chemical reaction in a solutionPair cations with other anion for both compoundsLiI(aq) + AgNO3(aq) →
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