Chemical Reactions&
Chemical Equations
Chemical Reactions
A process involving a substance or substances changing into a new substance or substances
Chemical Change
Chemical ReactionsEvidence of a chemical reaction
Chemical ReactionsEvidence of a chemical reaction
1) A permanent color change2) A gas is produced3) Energy is exchanged4) A precipitate is produced
Chemical EquationsA statement using chemical formulas to describe the identities and relative amounts of reactants and products involved in the chemical reaction
Reactant(s) Product(s)
MgCO3 MgO + CO2
MgCO3 CO2 + MgO
MgCO3 (s) MgO (s) + CO2(g)
Phases of Components(s) = solid(l) = liquid(g) = gas(aq) = aqueous
Physical Change Vs.
Chemical Change
Physical Change Chemical Change
Physical Change Chemical ChangePhase ChangesDissolvingMixingBreakingSeparatingFiltering
Rearrange AtomsNew Substances form
Did a chemical change occur?
1. Permanent Color Change Occurs
2. Precipitate Formed
3. Gas is Released
4. Energy is Exchanged – Temperature
Chemical Reaction Demonstration1. 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.
2. Gas is ProducedHCl (l) + Zn (s) ZnCl (Aq) + H2 (g)
3. Energy is ExchangedMg (s) + O2 (g) MgO (s)
Rapid Oxidation
4. Precipitate is FormedPb(NO3)2 (Aq) + K2CrO4 (Aq) KNO3 (Aq) + PbCrO4 (s)
Clear Bright Yellow
Practice Exercise #11. Define Chemical Reaction2. How do we know a chemical reaction has
taken place?3. What is a Chemical Equation and Why do
we use them?4. What are the initial constituents of a
chemical reaction? What are the end products called?
5. What do the following symbols stand for?s l g aq
Types of Chemical Equations
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
BalancingChemical Equations
Reactant(s) Product(s)
MgCO3 (s) MgO (s) + CO2(g)
Phases of Components(s) = (l) = (g) = (aq) =
1 MgCO3 (s) 1 MgO (s) + 1 CO2(g)
1 MgCO3 (s) 1 MgO (s) + 1 CO2(g)Reactants Products
1 MgCO3 (s) 1 MgO (s) + 1 CO2(g)
5 atoms 5 atoms
H2 + O2 H2O
2 H2 + 1 O2 2 H2O
H2 + H2 + O2 H2O + H2O
2 H2 + 1 O2 2 H2OH2 + H2 + O2 H2O + H2O
Ca + Cl2 CaCl2
Na + Cl2 NaCl
Fe2O3 Fe + O2
AgNO3 + NaCl NaNO3 + AgCl
FeS2 + O2 Fe2O3 + SO2
4 FeS2 + 11 O2 2 Fe2O3 + 8
SO2
NH4OH + Ni(NO3)2 NH4NO3 + Ni(OH)2
NH4OH + Ni(NO3)2 NH4NO3 + Ni(OH)2
Na2CO3 + Fe(NO3)3 Fe2(CO3)3 + NaNO3
Na2CO3 + Fe(NO3)3 Fe2(CO3)3 + NaNO3
3 Na2CO3 + 2 Fe(NO3)3 Fe2(CO3)3 + 6 NaNO3
Balanced!!!
H3PO4 + Ca(OH)2 Ca3(PO4)2 + H2O
NH4OH + H3PO4 (NH4)3PO4 + H2O
Al(OH)3 + H2SO4 Al2(SO4)3 + H2O
C6H6 + O2 CO2 + H2O