Chemical Reactions

Reaction Rates In all phases of matter, atoms and molecules exhibit random motion. This concept is part of the kinetic theory of matter. The speed at which atoms or molecules move depends on the state of matter and temperature.

When do reactions happen? Chemical reactions happen when atoms or molecules collide with enough energy (speed) and the correct orientation to combine by forming a bond.

18.2 Reaction Rates The reaction rate for a chemical reaction is the change in concentration of reactants or products over time. Reaction rates can be in 5 different ways.

Increase the Concentration Higher concentration means more molecules are present and that means a better chance for a collision and a reaction.

Raise the Temperature Higher temperature means the particles are moving faster which causes more collisions and a better chance for a reaction to happen.

More Surface Area More surface area means more molecules are exposed and they have a better chance of colliding and reacting.

Decrease the Volume of the Container This is the same thing as increasing the pressure (squeezing the molecules closer together). If the molecules are closer together they have a better chance of colliding and reacting.

18.2 Catalysts A catalyst is a molecule that can be added to a reaction to speed it up. Catalysts work by increasing the chances that two molecules will be positioned in the right way for a reaction to occur.

18.2 Chemical equilibrium A reaction may reach chemical equilibrium, the state in which the rate of the forward reaction equals the rate of the reverse reaction. In chemical equilibrium, the reaction can proceed both left and right simultaneously.

18.2 Chemical equilibrium