What affects the rate of a chemical reaction?
Temperature
Raising the temperature of the reactants increases the kinetic energy of the system. This means that the chance of molecules or atoms colliding with each other increases. Molecules or atoms need to collide in order to react. Cooling a reaction will slow it down by reducing the kinetic energy.
Concentration
Because molecules or atoms need to collide in order to react, increasing the concentration of the reactants increases the frequency of collisions. Molecules or atoms will still need sufficient energy to react for concentration to make a change in rate. In a reaction between a solid and solution, adding more of the solution will probably increase the rate of the reaction. Solution-solution reactions are a little trickier. Increasing the concentration of the weaker solution may speed up the reaction.
Try This: Reaction Rate Simulation You can change the temperature and the concentrations of the reactants. The total volume of reactants must equal 100 ml. After you set your concentrations and temperatures, press start. Then press the timer button. You will know that a chemical reaction has taken place when the beaker turns dark gray. |
Increasing Surface Area
Exposing more surface of a solid increases the molecules that can react. Grinding a solid into a powder speeds up the reaction compared to the same solid in block form.
Catalysts
Catalysts speed up chemical reactions. They do not become part of the product, but provide another pathway for the reaction to take place.
Pressure in a Reaction Between Two Gasses
Increasing pressure forces molecules closer together. By reducing the volume of the gas, the chance of a collision between molecules increases. An increase in pressure can also raise the temperature providing the energy necessary for a reaction to occur.