33Classifying Chemical Reactions SynthesisDecompositionSingle ReplacementDouble Replacement
34SynthesisTwo or more elements combine to form a more complex compound.A + B ABHand + kerchief handkerchiefExample: C + 2Cl2 CCl4
35Breaks down compounds into simpler substances. AB A + B DecompositionBreaks down compounds into simpler substances.AB A + BSchoolbook school + bookExample: 2Al2O3 4Al + 3O2
36ReplacementA reaction in which one element replaces another in a compound, or two elements in different compounds trade placesAB + C AC + B (Single)AB + CD AC + BD (Double)T.V. screen + door knob T.V. knob + screen doorHCl + NaOH H2O + NaCl
37Writing and Balancing Chemical Equations To describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.
38Writing and Balancing Chemical Equations CO2Subscript= IDENTIFIES THE NUMBER OF ATOMS IN A COMPOUND.
39Writing and Balancing Chemical Equations cont… Mg + O2 MgO22Coefficient is the number in front of the chemical formula that represents the # of molecules.
44Balancing Equations Activity Click the Active Art button to open a browser window and access Active Art about balancing equations.
45Balancing Chemical Equations Magnesium (Mg) reacts with oxygen gas (O2), forming magnesium oxide (MgO). To write a balanced equation for this reaction, first write the equation using the formulas of the reactants and products, then count the number of atoms of each element.Balancing Chemical Equations
46Balancing Chemical Equations Balance the equation for the reaction of sodium metal (Na) with oxygen gas (O2), forming sodium oxide (Na2O).
47Balancing Chemical Equations: Balance the equation for the reaction of tin (Sn) with chlorine gas (Cl2), forming tin chloride (SnCl2).
48Controlling Rates of Reaction Concentration: the more particles to react, the faster the reaction.
49Controlling Rates of Reaction cont… Surface area: the more particles that are exposed in a reaction, the faster it is.Temperature: If temperature is increased, then the rate of reaction increases.
50Controlling Rates of Reaction cont… Catalyst: Helps reaction happen by lowering activation energy.Inhibitor: Decreases rate of reaction.Enzyme : Biological catalyst in our bodies that allow important bodily functions to occur.
51Controlling Chemical Reactions Every chemical reaction involves energy in one of two ways:Exothermic: Energy is released.Endothermic: Energy is absorbed.