1. Physical Science Ch. 24

2. Section 1 Chemical Changes

3. Chemical ReactionChemical Reaction –Change in which one or more substances are converted into new substances ReactantReactant –Substances that react ProductsProducts –New substances produced

4. Chemical Reaction Left sideright side produce reactants  products yields

5. Lavoisier’s Contribution Scientist who carried out thousands of experiments to establish what we know as the Conservation of MassScientist who carried out thousands of experiments to establish what we know as the Conservation of Mass Conservation of MassConservation of Mass –Matter can neither be created nor destroyed it just changes forms

6.  Produces, yields, forms +Plus (s)Solid (l)Liquid (g)Gas (aq) Aqueous, substance dissolved in water

7. heat The reactants are heated light The reactants are exposed to light elec. An electric current is applied to the reactant

8. Chemical EquationChemical Equation –A way to describe a chemical reaction using chemical formulas and other symbols CoefficientsCoefficients –Tells the number of units of each substance taking place in a reaction –Only way to BALANCE a chemical equation

9. Section 2 Chemical Equations

10. Balancing Chemical Equations –Does not change the substances involved or what happens within a reaction, it only changes the way the reaction is REPRESENTED. Balanced Chemical EquationBalanced Chemical Equation –Same number of atoms on both sides of the equation

11. How to Balance Equations 1. Write chemical equation using symbols & formulas 2. List elements involved 3. List number of atoms for each element involved on each side 4.Choose coefficients to balance the equation 5. Recheck number of atoms for each element involved on each side

12. Things to remember when balancing equations Diatomic MoleculesDiatomic Molecules –Br, O, F, I, N, Cl, H Save Oxygen and Hydrogen to last to balanceSave Oxygen and Hydrogen to last to balance –Most times they balance themselves as other elements are balanced

13. 1.Al + Br 2  AlBr 3 2.Bi + O 2  Bi 2 O 5 3.Al + C  Al 4 C 3 4.AgS + Ni  NiS 2 + Ag 5.PbO + NaCl  PbCl 2 + Na 2 O

14. Al + Br 2  AlBr 3 AlBr 12121212 121212122 1313 1313 2Al + 3Br 2  2AlBr 3

15. Bi + O 2  Bi 2 O 5 BiO 12121212 12121212 12121212 121212122 2525 2525 4Bi + 5O 2  2Bi 2 O 5

16. Al + C  Al 4 C 3 AlC 11111111 11111111 111111111 4343 4Al + 3C  Al 4 C 3

17. AgS + Ni  NiS 2 + Ag AgSNi 111111111111 11111111 121121 1 2AgS + Ni  NiS 2 + 2Ag

18. PbO + NaCl  PbCl 2 + Na 2 O PbONaCl 1111111111111111 11111111 11221122 PbO + 2NaCl  PbCl 2 + Na 2 O

19. Section 3 Classifying Chemical Reactions

20. Types of Reactions 1.Synthesis 2.Decomposition 3.Single Displacement 4.Double Displacement

21. Synthesis Two or more substances reacting (combine) to form a new substanceTwo or more substances reacting (combine) to form a new substance A + B  AB 2H 2 + O 2  2H 2 O

22. Decomposition One substance reacting (decomposes or breaks down) to form two or more new substancesOne substance reacting (decomposes or breaks down) to form two or more new substances AB  A + B 2H 2 O  2H 2 + O 2

23. Single Displacement When one element replaces another element within a compoundWhen one element replaces another element within a compound AB + C  AC + B AB + C  CB + A Cu + 2AgS  CuS 2 + 2Ag

24. Double Displacement Positive ion of one compound replaces the positive ion of the other to form two new compoundsPositive ion of one compound replaces the positive ion of the other to form two new compounds AB + CD  AD + CB H 2 O + AgS  H 2 S + AgO

25. PrecipitatePrecipitate –An insoluble compound that comes out of solution during a double displacement reaction

26. Section 4 Chemical Reactions and Energy

27. More Energy Out Exergonic ReactionsExergonic Reactions –Chemical reactions that release energy Exothermic ReactionsExothermic Reactions –When the energy given off in a reaction is primarily in the form of heat

28. More Energy In Endergonic ReactionsEndergonic Reactions –When a chemical reactions requires more energy to break bonds than is released when new ones are formed –Energy absorbed can be in the form of light, heat, or electricity Endothermic ReactionsEndothermic Reactions –When energy needed is in the form of heat Endothermic refers not just to reactionsEndothermic refers not just to reactions –Also refers to physical changes –Epsom salt dissolving in water –Ice pack / Cold Pack

29. CatalystsCatalysts –A substance that speeds up a chemical reaction without being permanently changed itself When you add a catalysts the mass of the product formed remains the same, but it will form more rapidlyWhen you add a catalysts the mass of the product formed remains the same, but it will form more rapidly

30. InhibitorsInhibitors –Substances that are used to combine with one of the reactants to prevent certain reactions from occuring –Ex. Food preservatives They prevent chemical reactions that would cause the food to spoilThey prevent chemical reactions that would cause the food to spoil