Study of how quickly a reaction will proceed and factors affecting rate. Speed at which a reaction takes place is governed by several factors: increase concentration, increase temperature, presence of a catalyst increase rate. Rate is defined by comparing the change in the product / reactant concentration over time. Orders tell us how the rate changes when the concentration changes (exponent values) Products of a reaction do not normally appear in the rate law. Experimental method is used to facilitate monitoring the changes in a reactant or product. Half-life (t1/2) is the amount of time it takes to use up half of the reactant. Concentration or initial amount of the reactant doesn"t affect the half-life. Zero-order is not dependent on concentration, only on k. Second-order rates depend on k and the square of [a] Reaction coordinate is an abstract one-dimensional coordinate that represents progress along a reaction pathway. Collision theory explains various factors that influence reaction rates.