We explain what chemical phenomena are, their characteristics, classification and examples. Also, what are physical phenomena.
What are chemical phenomena?
Chemical phenomena are thermodynamic processes in which two or more substances, called reactants, change their molecular structure and generate new substances called products. The reactants or products can be chemical elements or compounds. Chemical phenomena are also called chemical reactions or chemical changes, terms that are synonymous.
In chemical phenomena, a significant change occurs in the matter, which is never the same at the beginning of the reaction as at the end, so that It is usually irreversible and not always observable to the naked eye. On the other hand, the amounts of matter and energy involved before and after the chemical reaction occurs always remain constant.
Chemical reactions are common in our daily lives and many of them are key in the manufacturing of products, obtaining energy and other processes of importance to society.
See also: Exothermic reaction
Types of chemical reactions
Before showing the different types of chemical reactions, it is important to know some of the symbols used to represent these reactions through chemical equations:
Chemical reactions are classified, first and foremost, according to the types of chemical compounds they involve. We will thus have organic and inorganic chemical reactions, and each type is classified independently:
Inorganic reactions. They are those that involve inorganic compounds, and can be classified:
- According to the rearrangement of the atoms of the reactants when they are transformed into products:
- Synthesis or addition reactions Two reactants combine with each other to result in a different substance.
- Decomposition reactions One substance reacts with another and breaks down into its simplest components.
- Substitution or simple displacement reactions One compound or element takes the place of another, within a larger or more complex compound, replacing it and leaving it free.
- Double substitution reactions Two reactants exchange compounds or chemical elements simultaneously.
- Synthesis or addition reactions Two reactants combine with each other to result in a different substance.
- Depending on the energy exchanged during the reaction:
- Endothermic reactions. They are reactions that absorb heat when they occur.
- Exothermic reactions. They are reactions that release heat when they occur.
- Reactions that need light to occur They are those that absorb light when they occur.
- Reactions that emit light when they occur They are those that when they occur emit energy in the form of light.
- Endothermic reactions. They are reactions that absorb heat when they occur.
- Depending on the reaction speed:
- Quick reactions They are reactions that occur in a very short time.
- Slow reactions They are reactions in which the formation of products from certain reactants takes a long time.
- Quick reactions They are reactions that occur in a very short time.
Organic reactions Organic reactions depend on the type of organic compound in question, since each functional group has a range of specific reactions: alkanes, alkenes, alcohols, ketones, aldehydes, etc.
Examples of chemical phenomena
Any chemical reaction is a good example of chemical phenomena, even those that occur inside our bodies. We can mention some simple cases:
- Oxidation. We can see this phenomenon in metals, especially in saline environments (since the salt acts as a catalyst, accelerating the reaction between oxygen and the metal), and it consists of the formation of a layer of rust (or oxide) on the surface of the metal. rusty. It also happens inside our bodies, since with the oxygen we take in when we breathe, we then proceed to oxidize glucose molecules, obtaining chemical energy.
- Combustion. It is a rapid oxidation reaction that can cause fire. For example, when we light a piece of paper with a match and watch it turn into ashes. These types of reactions involve a combustible material (paper) and an oxidizer (oxygen in the air) in the presence of an increase in temperature.
- Corrosion. It is the result of an electrochemical reaction of a material (usually a metal) with the surrounding environment. When a substance corrodes, it is deteriorated and can wear out, break or break. Materials such as wood, ceramics, some plastics and even human skin can also suffer from corrosion.
- The production of salts When an acid and a metal are mixed, as in the case of spilling the contents of old batteries into the remote control compartment of a television, a salt of some type is produced, depending on the metal and the acid.
Chemical phenomena and physical phenomena
The difference between physical phenomena and chemical phenomena has to do with the type of change brought about in matter. Physical phenomena are related to changes in shape and states in which the substance remains chemically the same, that is, they do not involve chemical reactions.
For example, if we freeze water, we can turn it into a solid (ice) without it ceasing to be made up of hydrogen and oxygen.
Instead, chemical phenomena reorganize the molecular structure of matter forming and breaking chemical bonds between atoms and creating new substances. This is because a chemical reaction occurs, generally irreversible, in which substances other than the initial ones are obtained.
For example, after burning a paper into ashes, we cannot restore it to its original condition.
References
- “Chemical reaction” https://es.wikipedia.org/
- “Chemical Phenomena” in Portland Public Schools (Spanish). http://www.pps.k12.or.us/
- “Chemical phenomena in life” https://www.nature.com/
