1. What is a chemical reaction?

2. Chemical Reactions Chapter 7

3. Physical Properties color melting point boiling point electrical conductivity specific heat density state (solid, liquid, or gas)

4. Physical Change Changes in physical properties melting boiling condensation No change occurs in the identity of the substance Example: Ice, rain, and steam are all water

5. Chemical Change Atoms in the reactants are rearranged to form one or more different substances Old bonds are broken; new bonds form Examples: Fe and O 2 form rust (Fe 2 O 3 ) Ag and S form tarnish (Ag 2 S)

6. Chemical Change Some signs (or evidence) of chemical change are: –a gas is produced, –the temperature changes, –a substance disappears, –a solid is formed –a color change occurs, –a new odor is produced.

7. Practice Classify each of the following as a 1) physical change or 2) chemical change A. ____ a burning candle B. ____ melting ice C. ____ toasting a marshmallow D. ____ cutting a pizza E. ____ polishing silver

8. Solution Classify each of the following as a 1) physical change or 2) chemical change A. __2__ a burning candle B. __1__ melting ice C. __2__ toasting a marshmallow D. __1__ cutting a pizza E. __2__ polishing silver

9. Chemical Reactions A CHEMICAL REACTION HAS OCCURRED IF THE SUBSTANCES AT THE END OF THE REACTION ARE DIFFERENT FROM THE SUBSTANCES AT THE START OF THE REACTION

10. Why is it important to balance equations? What has to be true about the products and the reactants?

11. A Chemical Reaction Reactants Products

12. Writing and Balancing Equations A chemical equation is a shorthand expression for a chemical change or reaction. word - equation:states in words mercury (II) oxide + heat mercury + oxygen bulky and cumbersome 2 HgO 2Hg + O 2

13. Writing and Balancing Equations General Format for Writing Equations 1.The reactants are separated from the products by an arrow that indicates the direction of the reaction. 2.The reactants are placed to the left and the products to the right of the arrow. A plus sign (+) is placed between reactants and between products when needed.

14. Writing and Balancing Equations 3. Conditions required to carry out the reaction may be placed above or below the arrow. A delta indicates heat is applied. 4. Coefficients 2 H 2 O are placed in front to balance the equation. One (1) is never placed there, it is just understood.

15. Writing and Balancing Equations 5. The physical state of a substance is indicated by the following symbols: (s) solid(l) liquid (g) gaseous (aq) aqueous: means water solution yields reversible reaction

16. Writing and Balancing Equations Atoms cannot be created nor destroyed by normal chemical reactions. This means we must have the same number and type of atoms in our products as we have in our reactants. ReactantsProducts

17. Matter Is Conserved H 2 + Cl 2 2 HCl ++ Total atoms=Total atoms 2 H, 2 Cl2H, 2 Cl Total Mass=Total Mass 2(1.0) + 2(35.5)2(36.5) 73.0 g=73.0 g

18. Writing and Balancing Equations Balancing Equations 1. First you must have the equation in symbol format, you cannot balance a word equation. 2.Balancing: a. Count and compare the number of atoms of each element on each side of the equation and determine those that must be balanced.

19. Writing and Balancing Equations Balancing Equations b. Balance each element one at a time, by placing whole numbers (coefficients) in front of the formulas containing the unbalanced element. It is usually better to balance in this order: metals, nonmetals, hydrogen, oxygen.

20. Writing and Balancing Equations A coefficient placed before a formula multiplies every atom in the formula by that number! 2H 2 SO 4 =4H’s2S’s8O’s c. re-check each time you balance an element to see if anything else has become unbalanced. Make adjustments as needed.

21. Writing and Balancing Equations d. Do a final check making sure that each element is balanced and that the smallest possible set of whole number coefficients has been used: 4HgO4Hg + 2O 2 incorrect 2HgO2Hg + O 2 correct

22. P r a c t i c e 1 NaOH Na 2 O + H 2 O 2NaOH Na 2 O + H 2 O Fe + O 2 Fe 2 O 3 4Fe + 3O 2 2Fe 2 O 3

23. P r a c t i c e 2 O 2 + H 2 H 2 O O 2 + 2H 2 2H 2 O Cl 2 + NaI NaCl + I 2 Cl 2 + 2NaI 2NaCl + I 2

24. P r a c t i c e 3 CO 2 + H 2 O C 6 H 12 O 6 + O 2 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 FeS + HCl FeCl 2 + H 2 S FeS + 2HCl FeCl 2 + H 2 S

26. Turn in Balancing Activity worksheet Balance the equations on the notes sheet.

27. P r a c t i c e 4 Al(NO 3 ) 3 + H 2 SO 4 Al 2 (SO 4 ) 3 + HNO 3 2Al(NO 3 ) 3 + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 6HNO 3

28. P r a c t i c e 5 Zn + HCl ZnCl 2 + H 2 Zn + 2HCl ZnCl 2 + H 2

29. P r a c t i c e 6 Al 2 O 3 + H 2 O Al(OH) 3 Al 2 O 3 + 3H 2 O 2Al(OH) 3

30. P r a c t i c e 7 Pb(NO 3 ) 2 + AlCl 3 PbCl 2 + Al(NO 3 ) 3 3Pb(NO 3 ) 2 + 2AlCl 3 3PbCl 2 + 2Al(NO 3 ) 3

31. Chemical Reactions Types of Chemical Reactions 1. Synthesis Reaction: Two reactants combine to give one product. A + BAB 2Mg + O 2 2MgO

32. Chemical Reactions Types of Chemical Reactions 2.Decomposition: A single substance is decomposed or broken down to give two or more different substances: ABA + B 2PbO 2 2PbO + O 2 2 Na HCO 3 Na 2 CO 3 + H 2 O + CO 2

33. Chemical Reactions Types of Chemical Reactions 3.Single - Displacement Reaction: One element reacts with a compound to take the place of one of the elements of that compound. A + BCB + AC Zn + 2HCl H 2 + ZnCl 2

34. Chemical Reactions Types of Chemical Reactions 4.Double - Displacement: Two compounds exchange partners with each other to produce two different compounds. AB + CDAD + CB NaCl + KNO 3 NaNo 3 + KCl

35. Chemical Reactions Types of Chemical Reactions 5.Combustion: A hydrocarbon reacts with oxygen to form carbon dioxide, water, and energy. C x H y + O 2 H 2 0 + CO 2 C 5 H 10 + O 2 H 2 0 + CO 2

36. Practice Balance and identify the type of reaction for the following equations: a)Cl 2 + NaBr NaCl + Br 2 b)Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4 c)C 2 H 4 + O 2 H 2 0 + CO 2 d)Na + Cl 2 NaCl e)H 2 O H 2 + O 2

37. Practice Balance and identify the type of reaction for the following equations: a)Cl 2 + 2NaBr 2NaCl + Br 2 (single replacement) b)Ca 3 (PO 4 ) 2 + 3H 2 SO 4 3CaSO 4 + 2H 3 PO 4 (double displacement) c)C 2 H 4 + O 2 2H 2 0 + 2CO 2 d) 2Na + Cl 2 2NaCl (synthesis) e) 2H 2 O 2H 2 + O 2 (decomposition)

38. Homework Complete the Homework sheet. Balance the equations and identify their type.

39. Chemical Reactions Heat in Chemical Reactions Energy changes always accompany chemical reactions. One reason why reactions occur is that the products attain a lower, more stable energy state than the reactants.

40. Chemical Reactions Heat in Chemical Reactions Reactions are either exothermic or endothermic. Exothermic reactions liberate heat: H 2 + Cl 2 2HCl + 185kJ ( exothermic) Endothermic reactions absorb heat: N 2 + O 2 + 181kJ2NO (endothermic)

41. Predicting Products in Chemical Reactions

42. Types of Reactions There are five types of chemical reactions we have talked about: 1.Synthesis reactions 2.Decomposition reactions 3.Single displacement reactions 4.Double displacement reactions 5.Combustion reactions You need to be able to identify the type of reaction and predict the product(s)

43. Steps to Writing Reactions Some steps for doing reactions 1.Identify the type of reaction 2.Predict the product(s) using the type of reaction as a model 3.Balance it Don’t forget about the diatomic elements! (BrINClHOF) For example, Oxygen is O 2 as an element.

44. 1. Synthesis reactions Synthesis reactions occur when two substances (generally elements) combine and form a compound. (Sometimes these are called combination or addition reactions.) reactant + reactant  1 product Basically: A + B  AB Example: 2H 2 + O 2  2H 2 O Example: C + O 2  CO 2

45. Practice Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas Solid Magnesium reacts with fluorine gas Aluminum metal reacts with fluorine gas

46. 2. Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds 1 Reactant  Product + Product In general: AB  A + B Example: 2 H 2 O  2H 2 + O 2 Example: 2 HgO  2Hg + O 2

47. Practice Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes Aluminum nitride decomposes

48. Practice Identify the type of reaction for each of the following, and write the balanced equation: N 2(g) + O 2(g)  BaCO 3(s)  Co (s) + S (s)  NH 3(g) + H 2 CO 3(aq)  NI 3(s)  Cobalt (III) Sulfide Nitrogen monoxide

49. 3. Single Replacement Reactions Single Replacement Reactions occur when one element replaces another in a compound. A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-). element + reactant  product + product A + BC  AC + B (if A is a metal) OR A + BC  BA + C (if A is a nonmetal) (remember the cation always goes first!)

50. Single Replacement Reactions Sodium chloride solid reacts with fluorine gas Aluminum metal reacts with aqueous copper (II) nitrate

51. 4. Double Replacement Reactions Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound reactant + reactant  product + product AB + CD  AD + CB

52. Double Replacement Reactions First and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  KNO 3(aq) + BaSO 4(s) 2

53. Practice Predict the products. Balance the equation 1.HCl (aq) + AgNO 3(aq)  2.CaCl 2(aq) + Na 3 PO 4(aq)  3.Pb(NO 3 ) 2(aq) + BaCl 2(aq)  4.FeCl 3(aq) + NaOH (aq)  5.H 2 SO 4(aq) + NaOH (aq)  6.KOH (aq) + CuSO 4(aq) 

54. Combustion Example C 5 H 12 + O 2  CO 2 + H 2 O Write the products and balance the following combustion reaction: C 10 H 22 + O 2  5 6 8

55. Mixed Practice State the type, predict the products, and balance the following reactions: 1.BaCl 2 + H 2 SO 4  2.C 6 H 12 + O 2  3.Zn + CuSO 4  4.Cs + Br 2  5.FeCO 3 