chemical substances

Chemistry

2022

We explain what chemicals are, how they are classified and some examples. Also, dangerous chemicals.

Each chemical substance has a fixed chemical composition.

What are chemicals?

A chemical substance or chemical species is understood to be a type of matter that it is chemically homogeneous and defined, that is, it has a fixed chemical composition.

They have the characteristic that their particles they cannot be separated by any physical mechanism. However, they may suffer Physical changes, chemicals or physicochemical when subjected to the appropriate conditions or reactions.

The changes depend on the nature of the substance, and may consist of changes in State of aggregation (such as cooling liquid water to obtain solid ice), or transformations in its chemical composition (such as the reaction between a acid and an alkali). In the latter case they become another substance.

The chemicals were interest for him human being since he took on the task of exploring the nature of things, especially the composition of matter, identifying what at the time he thought were the indivisible or fundamental forms of matter. However, from the alchemy from the ancient Greeks to chemistry In modern times, it has finally been possible to understand when something is chemically pure and when it is composed of several identifiable substances.

A chemical should never be confused with a mixture of any type. Chemical substances cannot be separated into their constituent elements using physical separation methods (decantation, filtration, distillation, evaporation). Instead, the components of a mixture can be separated using these methods. On the other hand, it is possible to use chemical methods (chemical reactions) to separate the elements that make up a chemical.

Types of Chemicals

Chemical substances can be of two types:

  • Simple substances. They are made up of a specified number of molecules of oneself chemical element. For example: the oxygen molecule (O2).
  • Compound substances. They are composed of two or more chemical elements, which form a stable and fixed structure. They are usually known as "chemical compounds”. For example: the molecule of Water (H2O).

Examples of chemicals

Carbon dioxide is made up of carbon and oxygen.

Some examples of chemicals are:

  • Water. Compound formed by hydrogen and oxygen (H2O).
  • Carbon dioxide. Compound made up of carbon and oxygen (CO2).
  • Ozone. Substance made up of oxygen molecules only (O3).
  • Graphite. Substance made up of carbon molecules only (C).
  • Glucose. Compound made up of carbon, oxygen and hydrogen molecules (C6H12O6).

Dangerous chemicals

Chemical substances have particular properties, depending on their nature and composition. This can often represent a chemical hazard for the health of human beings, animals or plants.

The severity of such damage will depend on the nature of the substance, its concentration and the time of exposure, as well as the route of contact. It is not the same, for example, to burn the skin with an acid, to ingest it and cause serious damage to the digestive system.

Broadly speaking, some of the dangerous chemicals can be:

  • Flammable substances. Substances capable of producing large amounts of heat, that is, they can start fires, once they are with the appropriate reagent or under certain conditions of temperature Y Pressure. For example: butane gas.
  • Explosive substances. Substances that, in the presence of certain elements or in the face of sudden movements that cause the momentary loss of their stability, react exothermicallythat is, they generate large and sudden amounts of heat and Energy, and they can burn and / or violate what is around them. For example: nitroglycerin.
  • Corrosive substances. Substances pH extreme (basic or acid) that in contact with the organic material they cause focused exothermic reactions, and produce chemical burns, or in extreme cases disintegrate organic matter they touch. They can also affect inorganic material. For example: sulfuric acid.
  • Toxic substances. Substances that react in a harmful way with the substances that make up the body, of animals and plants, unleashing reactions that threaten the stability of the life, that is, causing poisoning. Depending on the substance and concentration, the level of damage may be focused or general, immediate or gradual, and it may or may not be counteracted by an antidote. For example: arsenic.
  • Radioactive substances. Substances whose atoms have unstable nuclei. These substances emit ionizing radiation as alpha and beta particles, gamma rays, or free neutrons. Ionizing radiation alters the chemical makeup of the chemicals that come into contact with it. Radioactive substances are capable of contaminating living beings and to cause them not only burns, but mutations unpredictable genetics, or even the death. For example: uranium-235.
  • Carcinogenic substances. Substances that once introduced into the organism, trigger the reproduction messy of certain cells, that is, they cause cancer. For example: benzene.
  • Mutagenic substances. Substances that directly alter the DNA of living beings, unleashing unpredictable mutations that can lead to numerous diseases, and even be transmitted to offspring. For example: formaldehyde.
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