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Thursday Day 1:

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  1. Thursday Day 1: • Chemical Reactions Overview • Practice formula writing • Word and Chemical Equations!

  2. Unit 8: Chapter 8!Chemical Equations and Reactions p. 258 - 291

  3. Chemical Formula • a notation that uses chemical symbols with numerical subscripts to convey the relative proportions of atoms of the different elements in a substance • Example: CaSO4

  4. Chemical Reaction • The process by which one or more substances change to produce one or more different substances. • Atoms rearrange to form new substances. 2 Parts: • Reactants (the original substances) • Products (the substances that form)

  5. Evidence of a Chemical Reaction There are four signs of a chemical change (chemical reaction), what are they?? • Evolution of a gas (odor) • Formation of a precipitate (solid) • Release or absorption of energy/heat/light • Color change • More specific versions of these changes are listed in the book on pg. 261

  6. Evidences are not enough!! • To prove that a chemical change has occurred, a chemical analysis must be performed to prove that a new substance has formed • Properties of the new substance (density, melting point, boiling point) must be different from those of the original substance

  7. Word Equation • Describes a chemical reaction using words • Done before writing a chemical equation Example: • Methane + Oxygen  Carbon Dioxide + Water

  8. Formula Equation • A representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products • Example: • CH4 + O2 CO2 + H2O

  9. Sometimes heat or energy is needed or formed in a reaction. • If so, they are included in the word equation just like any other reactant or product.

  10. Chemical Equations often include states of matter of the reactants and products: • Abbreviations: • Solid (s) • Liquid (l) • Gas (g) • Aqueous (aq)—this means that the substance is in solution (is dissolved in water)

  11. Example 1: • Methane gas burns in gaseous oxygen, releasing energy, to form carbon dioxide gas and water vapor • Word Equation: • Methane + Oxygen  Carbon Dioxide + Water + Energy • Formula Equation: • CH4(g) + O2(g)  CO2(g) + H2O(g) + Energy

  12. Example 2: • Magnesium metal burns in oxygen gas with a bright white light to make a white powder called magnesium oxide. • Word Equation: • Magnesium + Oxygen  Magnesium Oxide + Energy • Formula Equation: • Mg(s) + O2(g)  MgO(s) + Energy

  13. Monday Day 2: • Check and go over word/chemical eqns • Start Balancing Chemical Equations • Balancing Activity

  14. Tuesday Day 3: • Start Balancing Chemical Equations • Balancing Activity • Balance equations!

  15. Law of Conservation of Mass • All chemical reactions must obey the law of conservation of mass • Atoms get rearranged, but are not created or destroyed • For this reason, all chemical equations must be balanced • The number of atoms of each element must be identical on the reactant side and the product side of a balanced chemical equation.

  16. Balancing Equations • To balance an equation, you must make the number of atoms of each element the same on the reactants side and on the products side • You CANNOT change the formulas of the substances • Do not change subscripts, or you will change the entire compound • You CAN change the coefficients in front of the formulas • A coefficient is small whole number that appears as a factor in front of a formula in a chemical equation

  17. Balancing Equations Activity • Please work on the Balancing Equations Activity using the materials provided – draw with colored pencils

  18. Example 1 & 2: • ___H2 + ___O2 ___H2O • ___HCl + ___K2CO3 ___KCl + ___H2O + ___CO2 2 2 2 2

  19. Example 3: • __(NH4)3PO4+__Pb(NO3)4__Pb3(PO4)4+__NH4NO3 • Hint: Polyatomic ions, when they stay intact, can be balanced as a unit 3 4 12

  20. Example 4: • __Na3PO4 + __Ca(NO3)2 __NaNO3 + __Ca3(PO4)2 2 3 6

  21. Odd-Even Technique • This can be used when you have an odd number of an element on one side, and an even number of that element on the other side • Typically done with diatomic elements, especially oxygen • Steps: • Balance everything except for the particular element • Double all other coefficients • Then determine the coefficient of the diatomic element

  22. Example 5: 2 9 6 6 • ___C3H6 + ___O2 ___CO2 + ___H2O

  23. Balancing Equations Practice • Practice balancing chemical equations on p.9-10

  24. Wednesday Day 4: • Check and go over balancing equations • Start Classifying Chemical Reactions

  25. Day 5: • Classifying Chemical Reactions (con’t)

  26. Why classify rxns? 5 types of reactions • Synthesis • Decomposition • Single Displacement • Double Displacement • Combustion • More easily predict the products that form • Different types of reactions follow certain patterns, making balancing easier

  27. Synthesis ReactionA + B  AB • A reaction in which two or more substances combine to form a new compound • Example: • N2 + 3H2  2NH3 Defining Features: • 2 elements or compounds combine into 1 product ONLY ONE PRODUCT

  28. Synthesis Reaction • Sometimes, more than one product can result • Predict the Products of the following: • Fe + S  • If Fe is +2 • If Fe is +3 • Answer: • FeS • Fe2S3

  29. Decomposition ReactionAB  A + B • A reaction in which a single compound breaks down to form two or more simpler substances • Example: • HgO  Hg + O2 Defining Features: • Compound breaks down into 2 or more parts ONLY ONE REACTANT

  30. Decomposition Reaction • Predict the Products of the following: • 2NI3(s)  • Answer: • N2(g) + 3I2(g)

  31. Single Displacement ReactionA + BX  AX + B • A reaction in which one element replaces another element in a compound • The single displacement reaction will only occur if A is more reactive than B • See the Activity Series • A cation can only replace a cation& an anion can only replace an anion (write charges above elements in eqns)

  32. Activity Series(p12 in P of F) • A series of elements that have similar properties and that are arranged in descending order of chemical reactivity • An element can only displace an element that is below it on the activity series • It is possible for no reaction to occur

  33. Single Displacement Reaction • Examples: • Br2 + 2NaI  2NaBr + I2 • Br2 + 2NaCl  No Rxn Defining Feature: More active element replaces the less active one SINGLE ELEMENT ON EACH SIDE OF REACTION

  34. Single Displacement Reaction • Predict the Products of the following: • Zn + Cu(NO3)2 • Cu + Zn(NO3)2  • Answers: • Cu + Zn(NO3)2 • No reaction

  35. Single Displacement Reaction • Predict the Products of the following: • Br2 + 2 NaI • Br2 + 2 NaCl  • Answers: • 2 NaBr + I2 • No reaction

  36. Double Displacement ReactionAX + BY  AY + BX • A reaction in which a gas, a solid precipitate, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds • Example: • HCl+ NaOHHOH + NaCl Defining Features: the ions switch ‘partners’ TWO COMPOUNDS ON EACH SIDE OF THE REACTION

  37. Double Displacement Reaction • Predict the Products of the following: (remember: write charges) • Na2S + Cd(NO3)2 • Answer: • 2NaNO3 + CdS

  38. Double Displacement Reaction • Predict the Products of the following: • 2RbNO3 + BeF2 • Answer: • 2RbF + Be(NO3)2

  39. Combustion ReactionHydrocarbon + O2(g)  CO2(g) + H2O(g) • The oxidation reaction of a compound, in which heat is released • Often used to generate energy • Example: • 2Mg + O2 2MgO • Most combustion reactions involve hydrocarbons or other carbon-based compounds • Example: • C3H8+ 5O2 3CO2+ 4H2O

  40. Combustion Defining Features: Compound burning with oxygen (O2 as a reactant) to produce oxides usually water and carbon dioxide OXYGEN (O2) = REACTANT or OXIDES FORM (WATER AND CARBON DIOXIDE)

  41. Combustion Reaction • Predict the Products of the following: • C6H12 + O2 • Answer: • CO2 + H2O

  42. Classifying Reactions Examples: • 2NaBr + Ca(OH)2 CaBr2 + 2NaOH • Double Displacement • 2NH3 + H2SO4 (NH4)2SO4 • Synthesis • 4C5H9O + 27O2 20CO2 + 18H2O • Combustion • 3Pb + 2H3PO4 3H2 + Pb3(PO4)2 • Single Displacement

  43. Classifying Reactions Practice • Practice classifying reactions on p. 9-10

  44. Thursday Day 6: • Go over Types of Rxns p.9-10 • Demos

  45. Friday Day 7: • Classifying & Predicting reactions

  46. Classifying Reactions and Predicting Products • 2HgO  • Answer • Decomposition • 2Hg + O2

  47. Classifying Reactions and Predicting Products • Br2 + 2 NaCl • Answer • Single Displacement • NO REACTION

  48. Classifying Reactions and Predicting Products • Zn + H2SO4 • Answer: • Single Displacement • H2 + ZnSO4

  49. Classifying Reactions and Predicting Products • Pb(ClO3)2 + 2KI  • Answer: • Double Displacement • PbI2 + 2KClO3

  50. Classifying Reactions and Predicting Products • 2NH4Cl + Pb(NO3)2 • Answer: • Double Displacement • 2NH4NO3 + PbCl2