Why Do Chemical Reactions Take Place?

Chemical reactions occur not just in a laboratory, but also throughout your body.

Chemical reactions are part of life. Without specific reactions occurring between chemicals on a minute-to-minute basis, life could not exist. The chemical reactions that occur regularly in nature help plants to grow and leaves to turn green--not to mention helping you digest your lunch.

What Is a Chemical Reaction?

A chemical reaction occurs when bonds between atoms in one compound break, and the atoms rearrange themselves with atoms from another compound where the bonds have broken. A chemical reaction may occur spontaneously as a result of a favorable energy change in the presence of other atoms. Bonds tend to form in the most stable conformation. Chemical reactions can occur on their own or with the help of an enzyme or energy source.

Types Of Chemical Reactions

According to the Virginia Tech University Department of Chemistry, four main types of chemical reactions exist:

Synthesis. In a synthesis reaction, two elements combine to form a compound. Many types of synthesis reactions exist; one of the more common combines a metal and a non-metal, such as sodium (Na+) and chloride (Cl-), to form sodium chloride (table salt).

Decomposition. The opposite of a synthesis reaction, a decomposition reaction occurs when the molecule formed in a synthesis reaction breaks back down into its individual components. A common way to decompose a compound is to apply heat.

Replacement. Replacement occurs when a more active metal takes the place of a less active metal or other element. The higher activity makes the new compound more stable.

Ionic Reaction. This generally occurs in an aqueous solution between two different compounds. Each of the compounds (consisting of at least two elements) will "swap elements" with the other compound, forming two new compounds.

Chemical Reactions Provide Energy

One of the most common chemical reactions in your body produces energy for your cells. A molecule of glucose goes through a long series of steps to create adenosine triphospate (ATP), the energy molecule of your body. Chemical reactions proceed to break down this molecule to its usable parts, which then are shuttled off to create the ATP. Without these chemical reactions to break down the glucose molecule, it would be very difficult to generate ATP for energy.

Why Do Chemical Reactions Occur?

What is the point of all this atomic rearrangement in chemicals and compounds? Why don't atoms just stay put? Gibbs Free Energy determines whether a chemical reaction will proceed spontaneously. The Gibbs Free Energy equation takes into account enthalpy, entropy and the temperature of a reaction. If a Gibbs Free Energy result is greater than zero, the reaction will proceed in reverse of the direction as written. With a result less than zero, the reaction will proceed forward as written.

Other Factors

While Gibbs Free Energy gives a textbook idea of whether a reaction will occur, this equation depends on equal amounts of all reactants. In nature, and in any biological system, the amounts of reactants can vary greatly. In a situation in which one reactant becomes absent or reduced, this is known as the "rate-limiting step." In a favorable reaction, whenever the rate-limiting reactant appears, the reaction will occur until that reactant is exhausted.

References

• Virginia Tech University: Types of Equations
• University of Arizona: Gibbs Free Energy and Chemical Reactions

Resources

• Smith College: Glycolysis Animation