Some of the ancient scientists believed that the world consists of a single substance in different forms.The general concept of matter exists today, yet the ancients were wrong.Because of this confusion, they came when we tried to get turn lead into gold.However, the physical processes of the alchemists went to chemical, creating a new science.Now every schoolchild knows well achiever signs of differences between these two processes.What is the chemical reactions?
Examples can be seen even in everyday situations.Many children watched my mother dampens soda with vinegar, and so get the best first impression of chemical reactions.But in some situations, you can pay attention to the child and to other manifestations.For example, iron rust and darkening of silver.It's also a chemical reaction.
return to the distinction processes mentioned earlier in this article.So, when the physical process does not change the substance of the molecule.The body can be made to change the shape, can be crushed to particles of a substance, you can change its physical state.But the composition of the particles will remain unchanged.You can crush aluminum spoon on the side or by using the enormous temperatures and pressures make it evaporate - but the body will be aluminum.
When a chemical reaction due rebuilt, although the substance may remain the same.For example, if you get a diamond from graphite, it is not necessary to consider the physical process and chemical as well as links with the rearranged.Although, as a rule, the composition of the material changes, Example diamond - exception.
Usually, chemical reactions associated with the release or absorption of energy.The latter manifests itself as heat.There thermoneutral reaction in which the thermal effect of zero.But they are quite a bit, most either require "infusion" of energy, or are themselves, and are accompanied by a change in temperature.The combustion process is further followed by another and release light.
But not always change the deep structure of matter can be called a chemical process.There is also the nuclear reactions.They affect matter on the atomic level.This last turn into atoms of another species - a chemical element.And it's a very complicated process, in which an enormous amount of energy is released.Suffice it to recall nuclear explosions, to understand what it was about.
To fix the processes, people began to use a special tool: the equation of chemical reaction.Left written materials which bear the name of the reactants, the right - food.Not everyone liked the school to arrange the coefficients in the equations.It must be said that these factors simply reflect the real processes, not created "out of my head" person.After all, the atoms do not arise out of nowhere.Modern students are lucky, they can learn formulas of substances, but the old had to rely only on the amount of product and reagent that is not always obvious.
How to distinguish between physical and chemical processes?More often release heat, gas or precipitate, discoloration.But this approach does not always work, and because of an open bottle of soda out pre-dissolved gas, mercury oxide by grinding can change color, and zinc oxide changes color when heated.The heat effect can be expressed very weakly, so that it is not easy to fix, so that such a chemical reaction can be detected by other reactions ....
in the science of materials has an interesting section - mechanochemistry.As a result of mechanical influences in special mills in matter occur free radicals, and it acquires new properties.For example, as manufactured aspirin in pharmaceuticals.Mechanically activated materials are more active chemical, which is important for medicine.
