For particles to react they must collide (with sufficient energy) The __________  the number of reactive collisions, the ____________ the rate of the reaction.

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t-nez | High School Teacher | (Level 3) Associate Educator

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The greater the number of reactive collisions, the greater the rate of the reaction.

Reaction rate is the decrease in concentration of a reactant with respect to time or the increase in concentration of a product with respect to time. More reactive collisions means that reactants are consumed faster and products are produced faster.

Reactive collisions are those in which reacting particles collide with enough speed and in the right orientation to produce a reaction. 

This explains why increasing the temperature usually speeds up a chemical reaction. Higher temperature means higher average kinetic energy, so molecules are moving faster, having more collisions, and colliding with greater speed. Some other factors that create more reactive collisions are increasing the concentration of reactants, increasing the surface area of reactants by using a form that has smaller particles and stirring the reaction mixture. All of these increase the rate of chemical reactions.