New Unit Energy and Reactions

1. New Unit Energy and Reactions

2. 1. Energy What is energy? Energy = ability to do work What is work? Work = TRANSFER of energy from one object to another.

3. 1. Energy • Energy exists in many forms • Kinetic • Potential • Thermal/Heat • Chemical • Electrical • Electromagnetic/Light • Mechanical • Nuclear • Sound

5. 1. Energy IMPORTANT Energy CANNOT be created or destroyed

6. 1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTEDfrom one form to another.

7. 1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTEDfrom one form to another.

8. 1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTEDfrom one form to another.

9. 1. Energy IMPORTANT Energy CANNOT be created or destroyed Energy is CONVERTEDfrom one form to another.

10. 1. Energy In this class: changes in bond energy in reactions and physical changes

11. 1. Energy Explain the conservation of energy Why might a one-step energy conversion be preferred over a two-step conversion?

12. 2. Physical vs Chemical Changes

13. 2. Physical Changes and Reactions How is a physical change different from a chemical change? Physical Chemical Example: Changing outfits Changing DNA

14. 2. Physical Changes and Reactions Signs of a chemical change Evolution of a gas Formation of something solid Change in appearance Change in energy

15. 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

16. 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

17. 2. Physical Changes and Reactions Endothermic Exothermic absorbs/needs energy releases energy

18. 2. Physical Changes and Reactions Show chemical changes with equations Reactants  Products  means “produces”

19. 2. Physical Changes and Reactions Writing Reactions Baking soda, NaHCO3 combines with acetic acid, HC2H3O2 to produce sodium acetate NaC2H3O2, carbon dioxide CO2, and water H2O.

20. Page 266 # 1,3,4,5,9,10,11,12

21. 3. Types of Reactions 5 main categories Synthesis Decomposition Combustion Single Replacement Double Replacement

22. 3. Types of Reactions Combustion Explanation: something with carbon + oxygen  Example: C6H12O6 + 6O2 6CO2 + 6H2O Pattern: Carbon + O2 CO2+ H2O

23. 3. Types of Reactions Synthesis Explanation: when two or more become one Example: H2 + O2 2H2O Pattern: A + B  AB

24. 3. Types of Reactions Decomposition Explanation: when one becomes two or more/breakup Example: 2H2O  H2 + O2 Pattern: AB  A + B

25. 3. Types of Reactions Single Replacement Explanation: Love Triangle Example: Zn + CuSO4 Cu + ZnSO4 Pattern: A + BC  B + AC

26. 3. Types of Reactions Double Replacement Explanation: Soap Opera Drama Example:KCl+ NaNO2 NaCl + KNO2 Pattern: AB + CD  AD + BC

27. 4. Balancing Reactions OBJECTIVE: Applying Conservation of Mass to Reactions

28. 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

29. 4. Balancing Reactions frame + wheels + chain + handlebars + pedals  1 bicycle 1 frame + 2 wheels + 1 chain + 1 handlebar + 2 pedals  1bicycle What are those numbers? COEFFICIENTS

30. 4. Balancing Reactions H2+ O2 H2O

31. 4. Balancing Reactions H2+ O2 2H2O

32. 4. Balancing Reactions 2H2+ O2 2H2O

33. 4. Balancing Reactions 2H2+ O2 2H2O NEVERchange subscripts

34. 4. Balancing Reactions 2H2+ O2 2H2O CH4 + 2O2 CO2 + 2H2O Cu + 2AgNO3 2Ag + Cu(NO3)2 2KI + Pb(NO3)2 PbI2 + 2KNO3 What are those numbers? COEFFICIENTS

35. 4. Balancing Reactions Strategy for Balancing Reactions Start with compound Add coefficients to balance Leave single elements, like O2, H2, Al, Cu, etc. for last. Use fractions if necessary. Simplify if necessary. If fractions used, simplify fractions as well. Check work. NEVER CHANGE SUBSCRIPTS! DO NOT SPLIT COMPOUNDS!

36. A) Identify type of rxn B) Balance • Na + O2Na2O2 • Al + S8Al2S3 • O2+ C6H12O6  CO2 + H2O • Na + NaNO3 Na2O + N2 • H3PO4+ KOH  K3PO4 + H2O • NH3+ O2 N2 + H2O

37. 4. Balancing Reactions Balancing Reactions with Polyatomic Ions Mg + OH- Mg(OH)2 HgCl2 + AgNO3 Hg(NO3)2 +AgCl Al + Hg(CH3COO)2  Al(CH3COO)3 + Hg

38. Identify type of rxn B) Balance • C2H6+ O2 CO2 + H2O • Al + HAsO3  H2 + Al(AsO3)3 • H3PO4 + Mg(OH)2 Mg3 (PO4)2 + H2O • NH4OH + H3PO4  (NH4)3PO4 + H2O • Al(OH)3 + H2SO4  Al2(SO4)3 + H2O • C10H22 + O2  CO2 + H2O (fractions?)

39. 4. Balancing Reactions How are coefficients different from subscripts? 2H2+ O2 2H2O subscripts= # of atoms

40. 4. Balancing Reactions How are coefficients different from subscripts? 2H2+ O2 2H2O coefficients = how many

41. 4. Balancing Reactions 2H2+ O2 2H2O subscripts= # of atoms coefficients = how many

42. 4. Balancing Reactions H2+ O2 H2O2 subscripts= # of atoms coefficients = how many

43. End of Chapter 8 Topics Covered Energy Physical vs. Chemical Changes Types of Reactions Balancing Reactions

44. Sample Problem Methane, CH4, reacts withO2 to combust and produce the following: CO2 and H2O. This reaction results in the release of a large amount of energy. Write a balanced reaction. This is what type of reaction? This reaction resulted in 49.1 grams of CO2. This is equal to how many moles? CH4 is a covalent compound. Draw its Lewis Structure