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Saturday, February 19, 2011

Endothermic and Exothermic Reactions

Sooo first of all, all chemical reactions involve changes in energy. Some release energy to the surroundings (exothermic) and others absorb it (endothermic)

Eg. Nuclear bombs give off energy and are exothermic reactions.
Eg. Ice starts to melt which absorbs energy and are endothermic reactions.

We use something called an Energy Diagram to chart the Potential energy of the chemicals as they change from reactants to products.

Before we get into the diagrams, here are a few vocabulary words you should consider remembering:

Energy of Reactants  -  total potential energy of all recatants in the reaction
Energy of Products  -  total potential energy of all products in the reaction
Energy of the Activated Complex  -  Potential energy of the "transition state" between reaction and products
Activiation Energy  -  the change in Enthalpy in Potential Energy during the reaction.
Change in Enthalpy  -  the energy that must be added to get the reaction to progress
If you still do not the concept of the Potential Energy Diagrams; watch this video.








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