Chemical reactions: why the alchemists are wrong

Some of the ancient scholars believed that the world consists of one substance in different forms. The general concept of matter still exists, but still the ancients were wrong. From this error they came about when they tried to make lead turn into gold. However, from physical processes, the alchemists turned to the chemical, creating a new science. Now every well-achiever knows the signs of the difference between these two processes. What is a chemical reaction?

Examples of them can be seen even in everyday situations. Many children observe how her mother extinguishes soda with vinegar, and so get the very first impressions of chemical reactions. But in some situations, you can pay attention to the child and other manifestations. For example, rusting of iron and darkening of silver. This is also a chemical reaction.

Let's return to the difference of the processes mentioned at the beginning of the article. So, in the physical process, molecules of matter do not change. The body can be made to change the shape, it is possible to break the substance into particles, you can change its aggregate state. But the composition of the particles will remain unchanged. It is possible to break an aluminum spoon into parts or with colossal temperatures and pressure to make it evaporate - but the body will remain aluminum.

When a chemical reaction occurs, the bonds are rearranged, although the composition of the substance may remain the same. For example, if you get a diamond from graphite, this should be considered not a physical process, but a chemical one, as the connections are rebuilt. Although, as a rule, the composition of substances varies, the example with diamond is an exception.

Usually, chemical reactions are associated with the release or absorption of energy. The latter manifests itself as warmth. There are also thermoneutral reactions, in which the thermal effect is zero. But they are very few, most either require "infusion" of energy, or go themselves and are accompanied by a change in temperature. The combustion process is additionally accompanied by the release of light.

But not always the change in the deep composition of matter can be called a chemical process. There are also nuclear reactions. They affect matter at the atomic level. At the same time, the latter turn into atoms of a different kind - a different chemical element. And this is a very complex process, in which a huge amount of energy is allocated. It is enough to recall nuclear explosions in order to understand what it is about.

To fix the ongoing processes, people began to use a special tool: the equation of chemical reaction. On the left are recorded substances that bear the name of reagents, on the right - products. Not everyone liked to place the coefficients in the equations in the school. I must say that these coefficients simply reflect real processes, and are not created "out of the head" by a person. After all, atoms do not arise out of nowhere. Modern schoolchildren are lucky, they can learn the formulas of substances, but the ancient ones had to rely only on the quantities of the product and reagent, which is not always obvious.

How to distinguish between physical and chemical processes? Most often on the release of heat, gas or precipitation, change in color. But this approach does not always work, after all, even in the open bottle with soda comes pre-dissolved gas, mercury oxide can change color when shredded, and zinc oxide changes color when heated. The heat effect can be very poorly expressed, so that it is difficult to fix, so that such chemical reactions can be detected with ... other reactions.

In the science of substances there is an interesting section - mechanochemistry. As a result of mechanical influences in special mills, free radicals appear in the substance , and it acquires new properties. For example, aspirin is manufactured in pharmaceutics. Mechanically activated substances are more active chemically, which is important for drugs.