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Chemical Reactions

Chemical Reactions. Chemical equation used to describe Chemical Reactions. Produce. Products. Reactants. Symbols in chemical reactions. (s) Solid Liquid (g) Gas ( aq ) Aqueous,solid dissolved in water Produces or yields.

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Chemical Reactions

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  1. Chemical Reactions

  2. Chemical equation used to describe Chemical Reactions Produce Products Reactants

  3. Symbols in chemical reactions • (s) Solid • Liquid • (g) Gas • (aq) Aqueous,solid • dissolved in water • Produces or yields

  4. Burning of Charcoal Carbon + Oxygen Carbon Dioxide Simplified to: CO2 (g) C (s) + O2 (g)

  5. Antoine Lavoisier • Law of conservation of mass: • Mass neither lost nor gained during a chemical reaction • Mass products = mass reactants

  6. Balancing Chemical Equations • Atoms of Reactants and Products must be balanced to satisfy law conservation of mass

  7. Types of Reactions

  8. Synthesis: two or more Substances react to form a Single substance A + B Ex: 2H2 (g) + O2 (g) AB 2H2O (l)

  9. Synthesis of Water An explosive reaction!

  10. Decomposition: Compound breaks Down into two or more simpler Substances AB A + B Ex: 2H2O (l) H2 (g) + O2 (g) electricity

  11. Electrolysis of water O2 gas H2 gas

  12. Single Replacement : “partner stealing” One element takes the place of another Element in a compound A + BC B + AC Cu + 2AgNO3 2Ag + Cu(NO3)2

  13. Double Displacement: “partner swapping” Two different compounds exchange Positive ions and form two new compounds (+) (+) AB + CD AD + BC Pb(NO3)2 + 2 KI PbI2 + 2KNO3 DD reactions usually form a gas or a precipitate

  14. Combustion: Substance reacts rapidly with oxygen always producing heat, carbon dioxide and water CH4 + 2O2 CO2 + 2H2O Methane oxygen carbon dioxide water

  15. Energy and Chemical Reactions

  16. Chemical Reactions In all chemical reactions: Energy is either: 1. Released 2. Absorbed

  17. Exothermic Reactions • Produces heat (feels warm) • More energy is released as products form, than is required to break bonds in reactants

  18. Endothermic Reactions • Reaction uses more heat than it gives off (feels cold) • more energy is required to break bonds than to form new ones

  19. Reaction Rates

  20. Reaction Rate • How fast a reaction is occurring • Increased rate = fast • Decreased rate = slow

  21. 5 Factors Affecting Reaction Rate • 1. Temperature: • Higher temp. = faster reaction

  22. 2. Surface area • Increasing surface area (crush into smaller pieces) = fasterreaction rate

  23. 3. Concentration of Reactants • Increasing concentration = faster reaction rate

  24. 4. Use of Catalyst • Catalyst: substance that speeds up a chemical reaction without being consumed

  25. 5. Stirring • Stirring increases reaction rate Stirrer used in industry

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