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New Unit Energy and Reactions
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1. Energy What is energy? Energy = ability to do work What is work? Work = TRANSFER of energy from one object to another.
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1. Energy Energy exists in many forms - Kinetic - Potential - Thermal/Heat - Chemical - Electrical - Electromagnetic/Light - Mechanical - Nuclear - Sound
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1. Energy IMPORTANT Energy CANNOT be created or destroyed
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1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTED from one form to another.
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1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTED from one form to another.
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1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTED from one form to another.
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1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTED from one form to another.
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1. Energy In this class: changes in bond energy in reactions and physical changes
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1. Energy 1. Explain the conservation of energy 2. Why might a one-step energy conversion be preferred over a two-step conversion?
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2. Physical vs Chemical Changes
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2. Physical Changes and Reactions How is a physical change different from a chemical change? PhysicalChemical Example: Changing outfitsChanging DNA
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2. Physical Changes and Reactions Signs of a chemical change 1. Evolution of a gas 2. Formation of something solid 3. Change in appearance 4. Change in energy
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2. Physical Changes and Reactions Both physical and chemical changes need energy or release energy Add energy to ice = water Ice melts = water and releases energy
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2. Physical Changes and Reactions Both physical and chemical changes need energy or release energy Add energy to match Match burns = releases energy as fire
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2. Physical Changes and Reactions Endo thermic Exo thermic absorbs/needs energyreleases energy
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2. Physical Changes and Reactions Show chemical changes with equations Reactants Products means “produces”
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2. Physical Changes and Reactions Writing Reactions Baking soda, NaHCO 3 combines with acetic acid, HC 2 H 3 O 2 to produce sodium acetate NaC 2 H 3 O 2, carbon dioxide CO 2, and water H 2 O.
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Page 266 # 1,3,4,5,9,10,11,12
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3. Types of Reactions 5 main categories Synthesis Decomposition Combustion Single Replacement Double Replacement
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3. Types of Reactions Combustion Explanation: something with carbon + oxygen Example: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O Pattern: Carbon + O 2 CO 2 + H 2 O
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3. Types of Reactions Synthesis Explanation: when two or more become one Example: H 2 + O 2 2H 2 O Pattern: A + B AB
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3. Types of Reactions Decomposition Explanation: when one becomes two or more/breakup Example: 2H 2 O H 2 + O 2 Pattern: AB A + B
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3. Types of Reactions Single Replacement Explanation: Love Triangle Example: Zn + CuSO 4 Cu + ZnSO 4 Pattern: A + BC B + AC
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3. Types of Reactions Double Replacement Explanation: Soap Opera Drama Example:KCl+ NaNO 2 NaCl + KNO 2 Pattern: AB + CD AD + BC
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4. Balancing Reactions OBJECTIVE: Applying Conservation of Mass to Reactions
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4. Balancing Reactions Conservation of Mass: cannot create or destroy mass this means: there needs to be the same number of atoms on both sides of reaction
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4. Balancing Reactions frame + wheels + chain + handlebars + pedals 1 bicycle 1 frame + 2 wheels + 1 chain + 1 handlebar + 2 pedals 1 bicycle What are those numbers? COEFFICIENTS
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4. Balancing Reactions H 2 + O 2 H 2 O
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4. Balancing Reactions H 2 + O 2 2H 2 O
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4. Balancing Reactions 2H 2 + O 2 2H 2 O
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4. Balancing Reactions 2H 2 + O 2 2H 2 O NEVER change subscripts
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4. Balancing Reactions 2H 2 + O 2 2H 2 O CH 4 + 2O 2 CO 2 + 2H 2 O Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2 2KI + Pb(NO 3 ) 2 PbI 2 + 2KNO 3 What are those numbers? COEFFICIENTS
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4. Balancing Reactions Strategy for Balancing Reactions 1. Start with compound 2. Add coefficients to balance 3. Leave single elements, like O 2, H 2, Al, Cu, etc. for last. 4. Use fractions if necessary. 5. Simplify if necessary. If fractions used, simplify fractions as well. 6. Check work. NEVER CHANGE SUBSCRIPTS! DO NOT SPLIT COMPOUNDS!
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A) Identify type of rxnB) Balance 1. Na + O 2 Na 2 O 2 2. Al + S 8 Al 2 S 3 3. O 2 + C 6 H 12 O 6 CO 2 + H 2 O 4. Na + NaNO 3 Na 2 O + N 2 5. H 3 PO 4 + KOH K 3 PO 4 + H 2 O 6. NH 3 + O 2 N 2 + H 2 O
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4. Balancing Reactions Balancing Reactions with Polyatomic Ions Mg + OH - Mg(OH) 2 HgCl 2 + AgNO 3 Hg(NO 3 ) 2 +AgCl Al + Hg(CH 3 COO) 2 Al(CH 3 COO) 3 + Hg
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A) Identify type of rxnB) Balance 1. C 2 H 6 + O 2 CO 2 + H 2 O 2. Al + HAsO 3 H 2 + Al(AsO 3 ) 3 3. H 3 PO 4 + Mg(OH) 2 Mg 3 (PO 4 ) 2 + H 2 O 4. NH 4 OH + H 3 PO 4 (NH 4 ) 3 PO 4 + H 2 O 5. Al(OH) 3 + H 2 SO 4 Al 2 (SO 4 ) 3 + H 2 O 6. C 10 H 22 + O 2 CO 2 + H 2 O (fractions?)
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4. Balancing Reactions How are coefficients different from subscripts? 2H 2 + O 2 2H 2 O subscripts = # of atoms
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4. Balancing Reactions How are coefficients different from subscripts? 2H 2 + O 2 2H 2 O coefficients = how many
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4. Balancing Reactions 2H 2 + O 2 2H 2 O subscripts = # of atoms coefficients = how many
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4. Balancing Reactions H 2 + O 2 H 2 O 2 subscripts = # of atoms coefficients = how many
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End of Chapter 8 Topics Covered 1. Energy 2. Physical vs. Chemical Changes 3. Types of Reactions 4. Balancing Reactions
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Sample Problem Methane, CH 4, reacts with O 2 to combust and produce the following: CO 2 and H 2 O. This reaction results in the release of a large amount of energy. 1. Write a balanced reaction. 2. This is what type of reaction? 3. This reaction resulted in 49.1 grams of CO 2. This is equal to how many moles? 4. CH 4 is a covalent compound. Draw its Lewis Structure
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