Controlling Chemical Reaction Lesson 10

Chemical Reaction Add vocab words to vocab sections https://www.youtube.com/watch?v=LjbJELjLgZg Diet Coke and Mentos Add vocab words to vocab sections Activation Energy: minimum amount of energy to start chemical reaction Concentration: amount of substance in a given volume Catalysts: material that increases the rate of reaction by lowering activation energy Enzyme: a catalyst that provides a surface for a reaction to take place Inhibitor: material used to decrease the rate of a reaction

Energy and Reactions Activation Energy Reactions won’t occur until they have enough energy Energy is used to break the bonds of the reactants  then the atoms begin to form new chemical bonds of the products Activation energy: minimum amount of energy needed to start a chemical reaction All chemical reactions need a certain amount of energy to get started Think about waking up for the day. You have lots of things to get done but need to muster the energy to get out of bed and start you day  chemical reactions need energy to start

Exothermic and Endothermic Exothermic Reaction Products have less energy that reactants after the reaction This difference is a result in a loss of heat Ex. Burning wood, gas, oil

Fill in the blank In an exothermic reaction, the ____________ have less energy than the ___________ The difference is a result from loss of _____________ An example of a exothermic reaction is ____________________ Products, result, heat, burning wood, gas, oil

Exothermic and Endothermic Endothermic Reactions Products have more energy than the reactants The reactions must continue to absorb energy to continue Heat absorption Ex. Baking bread, photosynthesis (chlorophyll is used to react CO2 plus H2O plus energy to make glucose and oxygen)

Fill in the Blank In Endothermic Reactions _____________ have ___________ energy than the reactants The reactions must continue to absorb __________ to continue Examples include _______________

Rates of Chemical Reactions Do not occur all at the same rate Chemist can change the rate of reaction by changing Surface area Temperature Concentration Using catalyst and inhibitors Explosion very fast , rusting metal very slow

Temperature Heating a substance causes particles to move faster Fast particles increase the reaction in one of two ways 1. coming into contact more often  more chances for a reaction to occur 2. faster particles have more energy  helps reactants get over the “hump” of the activation energy Reducing temperature slows down reactions

Fill in the blank Heating a substance causes particles to move ___________ Fast particles _____________ the reaction Reducing _________________ slows down the reaction

Concentration Increase the concentration = increase rate of reaction Ex. Adding a small spoonful of sugar to a glass of lemonade will make it but adding a large spoonful of sugar will make it even more sweet. The glass with more sugar has a high concentration of sugar Increasing concentration of reactants supplies more particles to react, therefore increasing the rate of reaction

Fill in the blank Increasing the concentration will increase the ________________ Increasing __________________ of reactants supplies more particles to react Rate of the reaction, concentration

Catalyst and Inhibitors Catalyst increases the rate of a reaction by lowering the activation energy Enzymes are catalyst that provide a surface for reactions to take place Very specific, each one affects only ONE chemical reaction Inhibitor: prevent reactants from coming together Slows down reactions Found in preservatives added to food