Reaction Rates

Reactions occur because two reactant atoms, ions, or molecules collide. Reactions only occur with favorable collisions Anything that increases the chance of a collision will increase the rate of a reaction.

Temperature As temp increases, particle motion speeds up. Faster particles are more likely to collide. Hi temp reacts faster. Cooling down reduces the reaction rate.

Surface area Only surface atoms react. The more a substance is ground up, the more surface atoms it has. Ground up substances react faster than chunks,

Concentration More relevant for liquids and aqueous solutions. More particles in an area will increase chances of a reaction. Higher concentration increases reaction rate. Adding water will lower the concentration and can quench a reaction.

Pressure Applicable to gases Hi pressure forces reactant particles together and increases reaction rate.

Catalyst Does not participate in the reaction: neither a product nor a reactant. Provides an alternate pathway for the reaction to take, one with a lower energy requirement.

Activation energy EA The amount of energy required to make a reaction go. The energy required to break the bonds of the reactants.

Energy descriptions Exothermic: releases energy. Like a fire Endothermic: absorbs energy: like a cold pack.

Endothermic reaction

Exothermic reaction

Potential energy diagrams tutorial http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm