2Evidence 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
3Representing 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
4Representing 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)
5Representing 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
6Balancing 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
7Balancing Equations Na (s) + Cl2 (g) → NaCl (s) H2 (g) + O2 (g) → H2O (l)AgNO3(aq) + Cu(s) → CuNO3(aq) + AgAl(s) + O2(s) → Al2O3
8Classifying Chemical Reactions 5 typesNeed to be able to recognize different types.Need to be able to predict products of different types of reactions
9Synthesis 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
10Combustion ReactionOxygen combines with a substance to produce heat and energy2H2(g) + O2(g) → 2H2O(g)All combustion are synthesis not all synthesis are combustion.
11Combustion 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.
12Decomposition 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)
13Single 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)
14Double 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
15Double Replacement Reactions Precipitate: a solid being produced during a chemical reaction in a solutionPair cations with other anion for both compoundsLiI(aq) + AgNO3(aq) →