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Chemical Reactions & Chemical Equations. Chemical Reactions. Chemical Change. A process involving a substance or substances changing into a new substance or substances. Chemical Reactions. Evidence of a chemical reaction. Chemical Reactions. Evidence of a chemical reaction.
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Chemical Reactions Chemical Change A process involving a substance or substances changing into a new substance or substances
Chemical Reactions Evidence of a chemical reaction
Chemical Reactions Evidence of a chemical reaction 1) A permanent color change 2) A gas is produced 3) Energy is exchanged 4) A precipitate is produced
Chemical Equations A statement using chemical formulas to describe the identities and relative amounts of reactants and products involved in the chemical reaction
Phases of Components (s) = solid (l) = liquid (g) = gas (aq) = aqueous MgCO3(s) MgO (s) + CO2(g)
Physical Change Chemical Change
Physical Change Chemical Change Phase Changes Dissolving Mixing Breaking Separating Filtering Rearrange Atoms New Substances form
Did a chemical change occur? • Permanent Color Change Occurs • Precipitate Formed • Gas is Released • Energy is Exchanged – Temperature
Chemical Reaction Demonstration • Permanent Color Change CuSO4(Aq) + Zn (s) ZnSO4 (Aq) + Cu (s) Blue Gray Clear Black The Zn and Cu are Switching, this is known as a single replacement Reaction. • Gas is Produced HCl (l) + Zn (s) ZnCl (Aq) + H2 (g) • Energy is Exchanged Mg (s) + O2(g) MgO (s) Rapid Oxidation • Precipitate is Formed Pb(NO3)2(Aq) + K2CrO4(Aq) KNO3(Aq) + PbCrO4(s) Clear Bright Yellow
Practice Exercise #1 • Define Chemical Reaction • How do we know a chemical reaction has taken place? • What is a Chemical Equation and Why do we use them? • What are the initial constituents of a chemical reaction? What are the end products called? • What do the following symbols stand for? s l g aq
Synthesis • Putting things together • Also known as Direct Combination. 2 Na + Cl2 = 2 NaCl 4 Al + 3 O2 = 2 Al2O3
Decomposition • Breaking things down/Taking apart • AKA Analysis 2 KClO3 = 2 KCl + 3 O2 3 MnO2 = Mn3O4 + O2
Single Replacement • Replacing one element in a compound with another element. 2 Al + 6 HCl = 2 AlCl3 + 3 H2 2 NaBr + Cl2 = 2 NaCl + Br2
Double Replacement • Switching one element from a compound with another element from a different compound. 2 AgNO3 + MgCl2 = 2 AgCl + Mg(NO3)2 HCl + NaOH = NaCl + H2O
Others • Combustion • Rapid Oxidation • XXXX + O2 CO2 + H2O • Oxidation • Add Oxygen (Combustion) • Reduction • Acid – Base Neutralization • Etc……
HW • Due Monday • Read & outline page 249-255
Exothermic Reactions • Release or give off heat. • Heat is a byproduct of the reaction. • Temperature increases as the bonds between products are formed. • Examples • Combustion, Respiration, Oxidation
Endothermic Reactions • Take in or absorb Heat from the surroundings. • Temperature decreases as the reaction progresses. • Heat is used to break bonds of reactants. • Decomposition or Analysis Reactions
Oxidation • Removing Electrons
Reduction • Adding Electrons
Rate of Reaction • Reactions occur at different speeds. • The time it takes for reactants to become products.
Catalysts • They speed up reactions without being affected themselves. • They stay the same • Enzymes in living organisms. • Lowers activation energy • The amount of energy needed to start a reaction.
Speeding Up Reactions • Temperature, Energy, Pressure, Surface Area, Concentration, Collisions, Catalyst.
Measuring Rates of Reactions • Measure Reactants • Measure Products
Reactant(s) Product(s)
Phases of Components (s) = (l) = (g) = (aq) = MgCO3(s) MgO (s) + CO2(g)
Reactants Products 1 MgCO3(s) 1 MgO (s) + 1 CO2(g)
5 atoms 5 atoms 1 MgCO3(s) 1 MgO (s) + 1 CO2(g)
H2 + H2 + O2 H2O + H2O 2 H2 + 1 O2 2 H2O
H2 + H2 + O2 H2O + H2O 2 H2 + 1 O2 2 H2O
Na2CO3 + Fe(NO3)3 Fe2(CO3)3 + NaNO3 3 Na2CO3 + 2 Fe(NO3)3 Fe2(CO3)3 + 6 NaNO3 Balanced!!!