Chemical Reaction Notes

Chemical Reaction NotesVocabulary ReviewPhysical Change A change in size, shape, or state of an object, yet does not change the actual object.

Chemical Change A change from one substance into another with different properties. Evidence includes: changes in color, odor, size, or energy either received or given off.

VocabularyChemical Reaction A process of chemical change occurring when compounds change bonds and creating new, different substances.Chemical Equation the explanation of a chemical reaction using symbols and numbers to show the atoms involved.Reactants Substances that exist before a reaction.Products Substances that are formed from a reaction.

Understanding Chemical EquationsThe point of a formula is to sum up and quickly explain a reaction that would otherwise be too long winded.

The reactants of one molecule of methane and two oxygen molecules produces the products of one carbon dioxide molecule and two molecules of dihydrogen monoxide.

producesCH4 + O2 + O2 CO2 + H2O + H2OReactants Products

Understanding Chemical EquationsCH4 + O2 + O2 CO2 + H2O + H2OReactants Products

is the same equation as 1 CH4 + 2 O2 1 CO2 + 2 H2O

is the same equation as CH4 + 2O2 CO2 + 2H2O

CH4 + 2O2 CO2 + 2H20Reactant SideAtomProduct SideCarbonHydrogenOxygenCounting Atoms in Reactions1144442 + 2 = 6) Are atoms created or destroyed in a chemical reaction?How do you know?

What does the picture on the right represent?

The products balance the reactants. There are exactly the same number of reactant atoms as there are product atoms. Furthermore, the mass on the left equals the mass on the right. Atoms are not created or destroyed. There is exactly the same number of each type of atom in the products as there are in the reactants. 7) In a physical change, like changing state from a solid to a liquid, the substance itself doesnt really change. Explain how is a chemical change different from a physical change?

In a chemical change a new substance with different properties is formed, but in a physical change it only changes size, shape, or state.C3H8 + 5O2 3 CO2 + 4 H2OReactant SideAtomProduct SideCarbonHydrogenOxygenMore Counting Atoms338810106 + 4 = 1 C4H10 + 13O2 8 CO2 + 10 H2OReactant SideAtomProduct SideCarbonHydrogenOxygen481020262616 + 10 = When Balancing YOU CAN NEVER CHANGE THE NUMBER IN THE SUBSCRIPTS. ONLY COEFFICIENTSConservation of MassWhen a chemical reaction happens, no atoms are created or destroyed.

The number of atoms in the reactants ALWAYS EQUALS the number of atoms in the products.

For a chemical equation to be correct, the equation must be balanced.

11N2 + H2 NH3

NH

KClO3 KCl + O2KClOWorked ExamplesNaCl + F2 NaF + Cl2NaClF

H2 + O2 H2O

HOWorked ExamplesWhat is a chemical change?A chemical change is when a new substance with different properties is formed from the reaction of the REACTANTS.HHHHOOVisualizing Equations2 H2 + 1O22 H2OHHHHOOVisualizing Equations4 H2 + 2 O24 H2OHHHHOOHHHHOOVisualizing Equations6 H2 + 3 O26 H2OHHHHOOHHHHOOHHHHOOLimiting Reactants6 H2 + 2 O24 H2O + 2H2HHHHHHHHOOHHHHOOLimiting Reactants6 H2 + 1 O22 H2O + 4H2HHHHHHHHOOCCHHHHOOCHONa1 C2H2O2 + 1NaHCO31 NaC2H3O2 + 1CO2 + 1H2OOOCCHHHHOOCHONaOOCCHHHHTypes of ReactionsSynthesis: (Building something)A+B ABExample2H2 + O2 2H2OEnd with 1 Product

Decomposition: (Destroying something)AB A +B Example2NH3 N2 + 3H2Begin with 1 ReactantTypes of ReactionsSingle Replacement: AX + B A + BXExample2K + MgBr2 2KBr + MgSwitch one partner

Double Replacement:AX + BY AY + BXExample 2 AlBr3+ 3 K2SO4 6 KBr + Al2(SO4)3Switch both PartnersTypes of ReactionsAcid Base:Make a Salt and WaterAOH + HB AB + H2OExample NaOH + HCl NaCl + H2O

Combustion: Make CO2 and WaterCxHy + O2 CO2 + H2OExample CH4 + 2O2 CO2 + 2H2O

Heat ReactionsExothermic in these types of chemical reactions, heat is given off in the process.Example: Burning Substance combines with Oxygen to form heat, Light, CO2 or Water. (Combustion)Temperature of products rises.

Endothermic in these types of chemical reactions, heat is absorbed in the process.Example: A cold pack that dissolves a solution in water takes in heat from surrounding environment.Temperature of products lowers.Exothermic Reaction in which heat energy is released. Exo means outside. Energy is released to the outside. Example: Burning Substance combines with Oxygen to form heat, Light, CO2 or Water. (Combustion)The Energy of products is lower than reactants, but the temperature of products is higher than reactants (with the excess heat generated)

Reaction ProgressExothermic ReactionReleases energyEnergy of products is lower than reactants. Endothermic Reaction in which heat energy is absorbed.Endo means in. Energy goes IN to the reaction. Example: A cold pack that dissolves a solution in water takes in heat from surrounding environment.The Energy of products is higher than reactants, but the temperature of the reactants is lower due to the absorbed energy.

EndoEndothermic Reaction

Absorbs energyEnergy of products is higher than reactants. Reaction ProgressExo or endo? Reaction ProgressEnergyExo or endo? Reaction ProgressEnergyPutting it all together! Remember Types of Reactions? S = Synthesis:A + B ABD = Decomposition:AB A + BSR = Single Replacement:AX + B A + BXDR = Double replacement:AX + BY AY + BXC= Combustion CxHy + O2 CO2 + H2O

Exo or Endo?

Reaction ProgressEnergy What type of reaction is this? C3H8 + 5O2 3CO2 + 4H2OcombustionExo or Endo?

Reaction ProgressEnergy What type of reaction is this? 2H2 + O2 2H2OsynthesisExo or Endo?

Reaction ProgressWhat type of reaction is this? 2AlBr3+3K2SO4 6KBr + Al2(SO4)3Double replacement Exo or Endo?

Reaction ProgressWhat type of reaction is this? 2NaCl + F2 2NaF + Cl2Single replacement Exo or Endo?

Reaction ProgressEnergy What type of reaction is this? 2KClO3 2KCl + 3O2decompositionRates of ReactionsTemperature When temperature is increases, molecular speed is increased, making reactions happen faster. If you slow down the speed (decrease temperature) then the reaction slows down as well.Temperature Up = Reaction Rate Up

Concentration The amount of substance in a given amount of volume. The higher the concentration, the faster the reaction because the molecules are closer together.Concentration Up = Reaction Rate Up

Surface Area the amount of the substance that is exposed increases the reaction rate because only outer molecules can actually react.Surface Area Up = Reaction Rate UpActivation Energy The minimum amount of energy needed to start a reaction.

Inhibitor Slows down reactions. Chemicals on cereal boxes slowing down the spoiling of foods.

Catalyst speeds up reactions without being used up in the process.

Enzymes Proteins that speed up reaction in your body

Activation Energy The amount of energy needed to start a reaction. The hill in the diagrams. You have to climb the hill before the reaction can start.

Catalyst Speeds up reactions without being used up or changed in the process. Lowers the activation energy of a reaction. It lowers the hill! (Analogy: Like a matchmaker setting up a couple.)

Would you rather be a catalyzed or uncatalyzed reaction?

Which do you think occurs more easily?

Is this exo or endothermic? c

A catalyst lowers the Activation Energy (the hill!) Catalysts you have heard about!Enzymes = Your bodys catalysts! Ex. Enzymes in your saliva help food be broken down FAST!

Can a person act like a catalyst?

A catalyst is a person who gets something started or speeds something up (MLKs speech, starting a club, a starting a winning streak on a sports team, etc).

taken from http://www.americanrhetoric.com/speeches/mlkihaveadream.htmnull352506.0