A chemical change is a process that modifies the structure and bonds of the molecules of one or more substances.
A change implies an alteration, modification or transformation . Chemical , for its part, is that linked to the properties and structure of a substance according to its composition.
A chemical change is the process that leads one or more substances (called reactants ) to modify their structure and the bonds of their molecules, becoming other substances called products . These changes can be represented symbolically using chemical equations.
Characteristics of a chemical change
The conditions surrounding the chemical change, also known as a chemical reaction or chemical phenomenon , affect the production of the products . In any case, there are values that remain constant, such as the total mass and electric charge.
Chemical changes are measurable and observable events that cause a change in the chemical composition of substances. Matter transforms and undergoes a mutation that is generally irreversible.
A chemical change can occur for multiple reasons. There may be a transfer of protons or electrons or a release or absorption of heat , for example.
In a chemical change an exchange of energy can occur.
Reduction-oxidation reactions
Reduction-oxidation reactions , also mentioned as redox reactions, are among the most common chemical changes. In this case, there is a transfer of electrons between the reactants that generates a modification of their oxidation states.
The reducing agent contributes electrons to the medium and increases its oxidation state (it is oxidized), while the oxidizing agent receives these electrons, reducing its oxidation state (it is reduced). The entire process causes a chemical change in the substances involved.
Types of chemical changes
Broadly speaking, we can say that there are two types of chemical changes: inorganic and organic. With respect to organic chemistry , there are two models in which the changes are divided, depending on whether they affect the oxidation states: redox reactions do affect them, while neutralization reactions do not.
Another possible classification for state changes takes into account the type of structure , and from there the following arise:
* synthesis : it is also called combination since in it the reactants are combined with each other to give rise to the origin of a new product;
* simple decomposition : when the splitting of a substance into its components occurs;
* decomposition by means of a reagent : for the decomposition of a substance to take place, the use of a reagent is necessary;
* substitution : some component of the reactants is replaced by a substance, so that the first one is released. This type of chemical change is also called displacement ;
* double substitution : it is also called double displacement , and occurs when the elements or groups of elements participating in the chemical change are exchanged.
According to the type of energy that is exchanged:
* in the form of heat : this group includes exothermic reactions, when the reaction system releases heat, and endothermic reactions, heat is necessary for the chemical change to take place;
* in the form of light : endoluminous reactions need light from outside while exoluminous reactions emit it;
* in the form of electricity : endoelectric reactions require the contribution of electricity , but exoelectric reactions produce it.
Finally, there is the classification according to the type of particles that are exchanged, which can be protons (in acid-base reactions ) or electrons (in oxidation-reduction reactions).
In organic chemistry we have chemical changes involving compounds such as alcohols, ketones, aldehydes, alkanes and alkynes, among others, which find their classification, chemical properties and reactivity in the functional group. A functional group is one or more atoms that are attached to a carbon chain .