1. LecturePLUS Timberlake1 Chapter 5 Chemical Reactions and Quantities Chemical Changes Balancing Chemical Equations

2. LecturePLUS Timberlake2 Physical Properties color melting point boiling point electrical conductivity specific heat density state (solid, liquid, or gas)

3. LecturePLUS Timberlake3 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

4. LecturePLUS Timberlake4 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)

5. LecturePLUS Timberlake5 Learning Check E1 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

6. LecturePLUS Timberlake6 Solution E1 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

7. LecturePLUS Timberlake7 Chemical Reaction A process in which at least one new substance is produced as a result of chemical change.

8. LecturePLUS Timberlake8 A Chemical Reaction Reactants Products

9. LecturePLUS Timberlake9 Learning Check E2 A. How does an equation indicate a change in the identity of the reacting substances? B. How did the yellow and green reactants combine? C. Did all the reactants form product? Why or why not?

10. LecturePLUS Timberlake10 Learning Check E2 A. How does an equation indicate a change in the identity of the reacting substances? The formulas of the reactants are different than the formulas of the products. B. How did the yellow and green reactants combine? 1 yellow combined with 1 green. C. Did all the reactants form product? Why or why not? No. There were more yellow reactants than green.

11. LecturePLUS Timberlake11 Writing a Chemical Equation Chemical symbols give a “before-and-after” picture of a chemical reaction ReactantsProducts MgO + CCO + Mg magnesium oxide to form carbon monoxide reacts with carbon and magnesium

12. LecturePLUS Timberlake12 Learning Check E3 12 oz of dough, 4 oz mushrooms, 12 slices pepperoni, 8 oz cheese and 5 oz tomato sauce are used to make a pizza. Write a recipe in words for putting together a pizza. How would you write the recipe as an equation?

13. LecturePLUS Timberlake13 Solution E3 Example: Combine 12 oz dough + 4 oz mushrooms + 12 slices pepperoni + 8 oz cheese + 5 oz tomato sauce and heat 30 minutes at 350°C to produce 1 pizza 12 oz dough + 4 oz mshrm + 12 pep + 8 oz chse 1 pizza + 5 oz tom sauce

14. LecturePLUS Timberlake14 Reading A Chemical Equation 4 NH 3 + 5 O 2 4 NO + 6 H 2 O Four molecules of NH 3 react with five molecules O 2 to produce four molecules NO and six molecules of H 2 O or Four moles NH 3 react with 5 moles O 2 to produce four moles NO and six moles H 2 O

15. LecturePLUS Timberlake15 A Balanced Chemical Equation Same numbers of each type of atom on each side of the equation Al + S Al 2 S 3 Not Balanced 2Al + 3S Al 2 S 3 Balanced

16. LecturePLUS Timberlake16 Law of Conservation of Mass In any ordinary chemical reaction, matter is not created nor destroyed

17. LecturePLUS Timberlake17 When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction but you may not change the subscripts.When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction but you may not change the subscripts. Changing the subscripts changes the compound.Changing the subscripts changes the compound. The subscripts tell you how many atoms of a particular element are in a compound.The subscripts tell you how many atoms of a particular element are in a compound. The coefficient tells you about the quantity, or number, of molecules of the compound.The coefficient tells you about the quantity, or number, of molecules of the compound.

18. LecturePLUS Timberlake18

19. LecturePLUS Timberlake19 The four basic steps to balancing a chemical equation. 1.First write the correct formula for the reactants and the products. 2.Find the number of atoms for each element on the left side. Compare those against the number of the atoms of the same element on the right side. 3.Determine where to place coefficients in front of formulas so that the left side has the same number of atoms as the right side for EACH element in order to balance the equation. 4.Check your answer to see if: –The numbers of atoms on both sides of the equation are now balanced. –The coefficients are in the lowest possible whole number ratios. (reduced) Steps to Balancing Equations

20. LecturePLUS Timberlake20 Some Suggestions to Help You Take one element at a time, working left to right except for H and O. Save H for next to last, and O until last. IF everything balances except for O, and there is no way to balance O with a whole number, double all the coefficients and try again. (Because O is diatomic as an element) Polyatomic ions that appear on both sides of the equation should be balanced as independent units.

21. LecturePLUS Timberlake21 Steps in Balancing An Equation Fe 3 O 4 + H 2 Fe + H 2 O Fe: Fe 3 O 4 + H 2 3 Fe + H 2 O O:Fe 3 O 4 + H 2 3 Fe + 4 H 2 O H: Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O

22. LecturePLUS Timberlake22 Balancing Equations Sodium phosphate + iron (III) oxide  sodium oxide + iron (III) phosphate Na 3 PO 4 + Fe 2 O 3 ----> Na 2 O + FePO 4

23. LecturePLUS Timberlake23 Balance Equations with Coefficients Coefficients in front of formulas balance each type of atom 4NH 3 + 5O 2 4NO + 6H 2 O 4 N = 4 N 12 H=12 H 10 O=10 O

24. LecturePLUS Timberlake24 Learning Check E4 Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O A. Number of H atoms in 4 H 2 O 1) 22) 43) 8 B. Number of O atoms in 4 H 2 O 1) 22) 43) 8 C. Number of Fe atoms in Fe 3 O 4 1) 12) 33) 4

25. LecturePLUS Timberlake25 Solution E4 Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O A. Number of H atoms in 4 H 2 O 3) 8 B. Number of O atoms in 4 H 2 O 2) 4 C. Number of Fe atoms in Fe 3 O 4 2) 3

26. LecturePLUS Timberlake26 Learning Check E5 Balance each equation. The coefficients for each equation are read from left to right A. Mg + N 2 Mg 3 N 2 1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1 B. Al + Cl 2 AlCl 3 1) 3, 3, 22) 1, 3, 13) 2, 3, 2

27. LecturePLUS Timberlake27 Learning Check E5 C. Fe 2 O 3 + C Fe + CO 2 1) 2, 3, 2,3 2) 2, 3, 4, 3 3) 1, 1, 2, 3 D. Al + FeO Fe + Al 2 O 3 1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1 E. Al + H 2 SO 4 Al 2 (SO 4 ) 3 + H 2 1) 3, 2, 1, 2 2) 2, 3, 1, 3 3) 2, 3, 2, 3

28. LecturePLUS Timberlake28 Solution E5 A. 3 Mg +N 2 Mg 3 N 2 B. 2 Al + 3 Cl 2 2 AlCl 3 C. 2 Fe 2 O 3 + 3 C 4 Fe + 3 CO 2 D. 2 Al + 3 FeO 3 Fe + Al 2 O 3 E. 2 Al + 3 H 2 SO 4 Al 2 (SO 4 ) 3 + 3 H 2

29. LecturePLUS Timberlake29 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