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Chapter 21 Section 4

Chapter 21 Section 4. Chemical Reactions and Energy. Chemical Reactions – Energy Exchanges. Energy can take the form of heat, light, sound, or electricity Chemical bonds are the source of this energy Breaking chemical bonds require energy Forming new chemical bonds releases energy.

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Chapter 21 Section 4

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  1. Chapter 21 Section 4 Chemical Reactions and Energy

  2. Chemical Reactions – Energy Exchanges • Energy can take the form of heat, light, sound, or electricity • Chemical bonds are the source of this energy • Breaking chemical bonds require energy • Forming new chemical bonds releases energy

  3. More Energy Out • Exergonic reaction – chemical reaction that releases energy • Less energy is required to break the original bonds than is released when new bonds form • As a result, some form of energy, such as light or heat is given off by the reaction.

  4. Heat Release • Exothermic reaction - when the energy given off in a reaction is primarily in the form of heat • Examples • Burning wood • Exploding dynamite

  5. More Energy In • Endergonic reactions – chemical reactions that absorb energy • Requires more energy to break bonds than is released when new ones are formed • The energy absorbed can be in the form of light, heat, or electricity

  6. Heat Absorption • Endothermic reactions - when the energy needed for a reaction is in the form of heat • Example - barium hydroxide (BaOH)2 and ammonium chloride (NH4Cl) in water

  7. Catalysts and Inhibitors • Catalyst - a substance that speeds up a chemical reaction without being permanently changed itself • Inhibitors – substances used to down a chemical reaction • Catalysts and inhibitors do not change the mass of product produced, they only change the rate at which it is produced • Catalysts and inhibitors are not used up in a reaction

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