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Physical Science

Physical Science. Ch. 24. Section 1. Chemical Changes. Chemical Reaction Change in which one or more substances are converted into new substances Reactant Substances that react Products New substances produced. Chemical Reaction. Left side right side produce

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Physical Science

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  1. Physical Science Ch. 24

  2. Section 1 Chemical Changes

  3. Chemical Reaction • Change in which one or more substances are converted into new substances • Reactant • Substances that react • Products • New substances produced

  4. Chemical Reaction Left side right 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 Mass • Conservation of Mass • Matter can neither be created nor destroyed it just changes forms

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

  7. Section 2 Chemical Equations

  8. 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 Equation • Same number of atoms on both sides of the equation

  9. How to Balance Equations • Write chemical equation using symbols & formulas • List elements involved • List number of atoms for each element involved on each side • Choose coefficients to balance the equation • Recheck number of atoms for each element involved on each side

  10. Things to rememberwhen balancing equations • Diatomic Molecules • Br, O, F, I, N, Cl, H • Save Oxygen and Hydrogen to last to balance • Most times they balance themselves as other elements are balanced

  11. Al + Br2 AlBr3 • Bi + O2  Bi2O5 • Al + C  Al4C3 • AgS + Ni  NiS2 + Ag • PbO +NaCl  PbCl2 + Na2O

  12. Al Br 1 2 1 2 2 Al Br 1 3 1 3 Al + Br2 AlBr3 2Al + 3Br2 2AlBr3

  13. Bi O 1 2 1 2 1 2 1 2 2 Bi O 2 5 2 5 Bi + O2  Bi2O5 4Bi + 5O2  2Bi2O5

  14. Al C 1 1 1 1 1 1 1 Al C 4 3 Al + C  Al4C3 4Al + 3C  Al4C3

  15. Ag S Ni 1 1 1 1 1 Ag S Ni 1 2 1 1 AgS + Ni  NiS2 + Ag 2AgS + Ni  NiS2 + 2Ag

  16. Pb O Na Cl 1 1 1 1 1 1 Pb O Na Cl 1 1 2 2 PbO +NaCl  PbCl2 + Na2O PbO +2NaCl  PbCl2 + Na2O

  17. Section 3 ClassifyingChemical Reactions

  18. Types of Reactions • Synthesis • Decomposition • Single Displacement • Double Displacement

  19. Synthesis • Two or more substances reacting (combine) to form a new substance A + B  AB 2H2 + O2  2H2O

  20. Decomposition • One substance reacting (decomposes or breaks down) to form two or more new substances AB  A + B 2H2O  2H2 + O2

  21. Single Displacement • When one element replaces another element within a compound AB + C  AC + B AB + C  CB + A Cu + 2AgS  CuS2 + 2Ag

  22. Double Displacement • Positive ion of one compound replaces the positive ion of the other to form two new compounds AB + CD  AD + CB H2O + AgS  H2S + AgO

  23. Precipitate • An insoluble compound that comes out of solution during a double displacement reaction

  24. Section 4 Chemical Reactionsand Energy

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

  26. More Energy In • Endergonic 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 Reactions • When energy needed is in the form of heat • Endothermic refers not just to reactions • Also refers to physical changes • Epsom salt dissolving in water • Ice pack / Cold Pack

  27. Catalysts • 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 rapidly

  28. Inhibitors • 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 spoil

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