Chemical changes are of the utmost importance to modern society. We see evidence of them every day, from the most mundane and pedestrian to the highly complex and analytical reactions performed in high-tech labs. Chemical changes occur whenever the chemical makeup of substances is altered, that is when bonds between atoms are broken or created, when new substances are formed.
One of the most classic examples of a chemical change is during the neutralization of an acid and a base. This breaks the bonds between the atoms in the acid and base, and creates new ones that will form liquid water and some form of salt. For example, if we choose to react aqueous sodium hydroxide with hydrochloric acid, we will produce water and sodium chloride, or table salt. We know that a chemical change has taken place because new substances have been formed that were not there before.
Another common chemical change is the process of photosynthesis that plants use to create glucose, energy and oxygen. The plants intake light, carbon dioxide and water to chemically form new products. Because of the evident breaking and re-forming of bonds, we know that a chemical reaction has taken place.
When a metal is brought into contact with oxygen for an extended period of time, it undergoes the process of oxidation. This has the effect of transferring electrons between entities, and is generally seen as the formation of reddish-brown iron (IV) oxide, or rust. The creation of a new compound makes it evident that chemical change has taken place.
In order to determine whether or not a chemical change has taken place (as compared to a physical change), there are numerous effects that one must identify. A drastic change in energy levels (either an increase or decrease) that is solely caused by the reactants should alert one to the fact that a chemical change has taken place. As well, a change in colour, odor or form may signify a chemical change, but this evidence has not been proved absolutely.
Chemical changes have a drastic impact on how society functions. Whether one is baking a cake, preparing a science experiment, or performing maintenance on a physical structure, there is a great deal of scientific knowledge that can be gained from the study of chemical changes. Even the most mundane changes can be the results of the formation of intra molecular bonds, and these are made manifest in our lived world.