conquer the Chemistry EOC: Balancing Equations and Stoichiometry

1. conquer the Chemistry EOC: Balancing Equations and Stoichiometry

2. Chemistry TEKS • 8 (A) define and use the concept of a mole; • 8 (B) use the mole concept to calculate the number of atoms, ions, or molecules in a sample of material; • 8 (C) calculate percent composition and empirical and molecular formulas; • 8 (D) use the law of conservation of mass to write and balance chemical equations; and • 8 (E) perform stoichiometric calculations, including determination of mass relationships between reactants and products, calculation of limiting reagents, and percent yield.

3. IPC TEKS • 7(C) demonstrate that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products; • 7(D) analyze energy changes that accompany chemical reactions such as those occurring in heat packs, cold packs, and glow sticks and classify them as exothermic or endothermic reactions;

4. 8th TEKS • 5(D) recognize that chemical formulas are used to identify substances and determine the number of atoms of each element in chemical formulas containing subscripts; • 5(E) investigate how evidence of chemical reactions indicate that new substances with different properties are formed; and • 5(F) recognize whether a chemical equation containing coefficients is balanced or not and how that relates to the law of conservation of mass.

5. Label the Parts of an Equation

6. Why Balance Equations? • Law of Conservation of Mass – Matter cannot be created or destroyed it can only change forms. • In chemical reactions the number and mass of atoms on the reactant side of the equation must equal the number and mass of atoms on the product side of the equations.

7. Chemical Equations • Recipe for a chemical reaction • Relative number of reactants and products • Coefficients represent the relative numbers. CH4 + 2O2 CO2 + 2H2O

8. Law of Conservation of Matter: BalancingChemical Equations • Atoms are conserved in a chemical reaction. • Coefficients are manipulated to balance chemical reactions and create equivalent measures. • Identities cannot be changed. _C2H5OH (l) + _O2 (g)  _CO2 (g) + _H2O (g)

9. BalancingChemical Equations C2H5OH (l) + O2 (g)  CO2 (g) + H2O (g) Count Atoms: Carbon 2 Carbon 1 Hydrogen 6 Hydrogen 2 Oxygen 3 Oxygen 3

10. BalancingChemical Equations C2H5OH (l) + O2 (g)  CO2 (g) + H2O (g) C2H5OH (l) + 3O2 (g)  2CO2 (g) + 3H2O (g)

11. Chemical Equations as Equivalents • Coefficients from a balanced equation represent the number of theoretical mole equivalents and can be used in stoichiometric calculations.

12. 8th grade released question

15. Jelly Bean Equations andChemical Equation Cards

16. Online Balancing Equation Practice • http://sciencespot.net • Click Kid Zone • Click Matter & Atoms Go to: Balancing Equations Online Balancing Equations Online 2 • http://funbasedlearning.com/chemistry/chemBalancer3/worksheet.htm

17. Balancing Equation Strips • Draw a strip • Balance the equation • Write a word equation describing the reaction • Make or demonstrate a representation of the equation

19. Chemical Reaction Types

24. Synthesis(Combination, Composition) • Two or more substances combine to form a single substance. • General equation: A + B  AB example: 2Na + Cl2  2NaCl

25. Decomposition • A compound is broken into two or more products. • General equation: AB  A + B example: 2H2O 2H2 + O2

26. Single Replacement A + BC AC +B

27. Activity Series • For an element to replace another the lone element must be more active than the element it is replacing in the substance. • See the reference chart behind your periodic table.

28. Example: Zn+ 2 HCl ZnCl2 + H2

29. Example: Thermite Reaction 2 Al + Fe2O3 Al2O3 + 2 Fe

30. Example: 2NaBr (aq) + Cl2 (g) 2NaCl (aq) + Br2 (g)

31. Double Replacement(Double Displacement) AB + CD  AD + CB

32. Double Replacement Reactions • Occur in aqueous solutions • For a DR reaction to occur one of the following must happen: • A precipitate is formed (an insoluble or slightly soluble solid). • A molecular compound (usually water is formed). • A gas is formed. • Follow Solubility Rules

33. Example: Production of a PrecipitateSilver Nitrate + Sodium Chloride • Precipitate AgCl (s)

35. Chemistry Released

37. Chemistry Released

42. The Mathematics of Chemistry Stoichiometry Dimensional Analysis

43. Stoichiometric Calculation Plan • Write the chemical equation • Balance the chemical equation • Follow the steps of dimensional analysis • Start with what is given • Set up a series of equivalent measures • End with your goal • Solve the problem by cancelling units • Record the appropriate answer with units

44. Stoichiometry • Stoichiometry is a branch of chemistry that deals with the relative quantities of reactants and products in chemical reactions. • Greek root words: • Stoicheionmeaning " element“ • Metronmeaning "measure"

45. What is Dimensional Analysis? • Using the units, or dimensions, of measurements to express and calculate chemical quantities

46. What is the relationship? • Dimensional analysis is a strategy used for doing stoichiometric calculations.

47. What are some common equivalent measurements? • 1 inch =______centimeter(s) • 1 week = ______ day(s) • 60 seconds = ______minute(s) • 1 lb =______ ounce(s) • 1 cup = _____ fluid ounces • 1 tablespoon = _____ teaspoon(s) • 4 quarts = _____ gallon(s)

48. Common Equivalent Measurements • 1 mile = _____ feet • 1 kg = _____ 2.2 lb • 1 ft = ____ inches • 365 days = _____ year(s) • 1 ton = _____ pounds

49. Dimensional Analysis –The Plan • What is given? Start your calculation with this quantity with units. • What is your goal? What you are solving for is your goal and should be on top of the last step of the problem. • Set up a series of equivalent measures that cancels out all units except the goal units. 4. Solve the problem, and remember to mark through the cancelled units. 5. Record the appropriate answer with units.

50. Give it a try!How many seconds are there in 5.5 days? Follow the steps: • What is given? 5.5 days • What is your goal, and what are the units? Determine # of seconds in 5.5 days • Set up a series of equivalent measure that cancels out all units except the goal units. Get started: **What fractions “equal to 1” help transition from days to seconds?