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17-3 Controlling Chemical Reactions

17-3 Controlling Chemical Reactions. Getting Reactions Started. ACTIVATION ENERGY . All chemical reactions involve a change in energy. ACTIVATION ENERGY minimum amount of energy needed to start a reaction (electric spark, match, etc; some reactions get their activation

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17-3 Controlling Chemical Reactions

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  1. 17-3 Controlling Chemical Reactions

  2. Getting Reactions Started ACTIVATION ENERGY All chemical reactions involve a change in energy ACTIVATION ENERGY minimum amount of energy needed to start a reaction (electric spark, match, etc; some reactions get their activation energy from the heat in solution) A + B C + D

  3. Energy in chemical reactions EXOTHERMIC REACTION releases energy in the form of heat ENDOTHERMIC REACTION absorbs energy and the surroundings cool Absorbs Energy Releases Energy

  4. Rates of Chemical Reactions • Rate of a chemical reaction depends on how easily particles get together • More collisions means a faster chemical reaction, fewer collisions means a slower chemical reaction • RATE is affected by CONCENTRATION, SURFACE AREA, & TEMPERATURE, they do NOT affect activation energy, just allow more particles to “climb the hill” • INHIBITORS slow down reactions (wood pulp in dynamite) • SURFACE AREA • CONTAINS AN • INHIBITOR • TEMPERATURE • CONCENTRATION Indigestion, chew your food? Sugar dissolves in hot tea or ice tea? Tsp or tbsp of sugar in lemonade?

  5. Catalysts and Enzymes • CATALYST is a material that increases the rate of a reaction by LOWERING the activation hill • Catalysts are involved in reactions, but are not reactants; they are not changed in a reaction • ENZYME is a biological catalyst (allow reactions to take place at body temperature) ENZYME CATALYST

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