Energy and Chemical Reactions Endothermic Reaction n Ex

Energy and Chemical Reactions Endothermic Reaction n Ex Energy a part of the reactants Energy needs to keep being added in to keep reaction going Products have more energy than reactants Energy + NH 4 NO 3 NH 3+ HNO 3 (energy is written as one of the reactants) n

Energy and Chemical Reactions Graph of endothermic reaction n n Energy of the system increases as energy enters flows in from the surroundings.

Consider all steps in process 1. Heating system increases Eth of reactant molecules 2. Energy is transferred from Eth to Ech now stored in new arrangement of atoms 3. Resulting system is cooler - requires continued heating to bring Eth back up to level required to sustain reaction n Energy Bar Chart

Energy and Chemical Reactions n Exothermic Reactions n n n Example n n Energy is part of the products Energy is released as part of the reaction Reactants have more energy than products Zn + 2 HCl Zn. Cl 2 + H 2 + Energy (energy is written on the product side)

Energy and Chemical Reactions Graph of exothermic reaction n n Energy of the system decreases as energy flows out to the surroundings.

Consider all steps in process 1. Decrease in Ech results in increased Eth 2. System is now hotter than surroundings 3. Energy eventually moves from system to surroundings via heating n Energy Bar Chart for an Exothermic Reaction