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Endothermic and Exothermic Reactions. Endothermic. in. heat. Endo= ? Therm = ? What does endothermic mean? A chemical reaction that needs energy added to it for the reaction to take place (energy is taken IN when it occurs). Exothermic. out. heat. Exo = ? Therm = ?
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Endothermic in heat • Endo= ? • Therm = ? • What does endothermic mean? • A chemical reaction that needs energy added to it for the reaction to take place (energy is takenINwhen it occurs).
Exothermic out heat • Exo = ? • Therm = ? • What does exothermic mean? • A chemical reaction that gives off energy when the reaction takes place (energy is EXitingwhen it occurs).
Properties of Endothermic Reactions • If energy goes IN for the reaction to occur, would energy be a reactant or a product? • Energy is a reactant • If energy is ABSORBED, would it feel hot or cold to the touch? • It would feel cold--it’s absorbing energy from the surroundings
Properties of Exothermic Reactions • If energy EXITS when the reaction occurs, would energy be a reactant or a product? • Energy is a product • If energy is RELEASED, would it feel hot or cold to the touch? • It would feel hot--it releases energy to the surroundings
Examples of Endothermic Reactions • Cold packs • Evaporation of water • Melting of ice
Demonstration of Endothermic Reaction • NH4Cl(cr) + H2O(l) + energy --> NH4+(aq) + Cl-(aq) + H2O(l) • What are the reactants? • What are the products? • What are the states of matter?
Examples of Exothermic Reactions • Hot Packs • Burning coal • Freezing ice
Demonstration of Exothermic Reactions 2 3 • Al + CuCl2 --> Cu + AlCl3 + energy • What are the reactants? • What are the products? • Can you balance the equation? • What are the states of matter? • Heat pack (cr) (aq) 2 3 (cr) (aq)
Is it Endothermic or Exothermic? • When a lit match is placed in alcohol, the alcohol ignites producing light and heat. • Energy in the form of electricity can be added to water to break apart the water molecules into hydrogen gas and oxygen gas. • When ammonium chloride mixes with water, the solution formed feels cold. • A piece of wood placed in a furnace gives off heat and light before turning to ash.