What Makes Chemical Reactions Occur More Quickly?

Fire increases chemical reaction rates.

Chemists sometimes need to increase chemical reaction rates to finish an experiment within a certain amount of time. Reaction rate increases are also important in biological processes, especially breathing, digestion and movement. You can speed up reaction rates by adding energy, other chemicals and higher concentrations of the reacting chemicals.

Heat

Heat speeds up chemical reactions. Scientists often place a mixture of chemicals above a flame to warm up the mixture. The heat makes atoms in the mixture move around faster, since they now contain more energy, which makes them more likely to crash into each other and react to create a new compound.

Light

Light also accelerates chemical reactions. Instructions for chemical experiments often include light exposure. In addition, many chemicals are stored in containers with darkly tinted glass, so that they do not react. (This is also common when storing wine and beer.) The photons in light add energy to electrons when they collide with one another, which provides additional energy to the atom.

Catalysts

Chemical reaction rates also increase by adding catalysts. A "catalyst" is a chemical that makes other chemicals in a mixture react faster. Catalysts may change shape during the course of the reaction, but they return to their original shape after the reaction so they are available to speed up additional chemical reactions afterward.

Scientists select specific catalysts to speed up a single reaction. Often, chemicals in a solution react to form several different products, so selecting the correct catalyst increases the speed of the preferred chemical reaction, leading to a higher final concentration of the desired product.

Movement

Movement can also speed up chemical reaction. A chemist stirs the mixture of chemicals as a cook stirs a pot of soup. Stirring the materials makes them collide other faster; the movement also adds energy to the atoms in the mixture. Stirring the mixture also introduces more air into it, and the additional oxygen may also accelerate the reaction.

Concentration

Chemical reaction rates increase when changing the concentration of chemicals. Experiment procedures often call for adding one chemical to excess. This is usually the cheapest compound used in the reaction. Adding a large quantity of the inexpensive chemical ensures that the target chemical quickly collides with the excess chemical and reacts with it.

References

• Washington State University: Catalyst Surface Chemistry
• University of Tennessee at Martin: Factors Affecting Rate of Reactions
• University of Wisconsin at Madison: The Rate of a Reaction