Chemical reactions can take place at different speeds.Some of them are completed within a few seconds, while others may extend for hours, days, or even decades.To determine the performance and size of the necessary equipment as well as the amount of manufactured product, it is important to know the speed with which chemical reactions take place.It can have different values depending on:
the concentration of reactants;
is the temperature of the system.
Swedish scientist S. Arrhenius in the late nineteenth century was derived equation which relates the speed of a chemical reaction on this indicator, the activation energy.This figure is constant and determined by the nature of the chemical interaction of substances.
By the scientist reacted with each other may enter only those molecules which are formed out of the ordinary and are in motion.Such particles have been called active.The activation energy - it is the power that is needed for the transition of conventional molecules in a state in which their movements and reactions are the fastest.
In the process of chemical interactions among the particles of matter are destroyed and others arise.This changing relationship between them, that is, the electron density is redistributed.The rate of a chemical reaction, in which the interaction of old would be completely destroyed, would have a very low value.When this amount of energy must be imparted to high.Scientific studies have shown that in the course of the interaction of substances any system forms an activated complex, which its transitional state.At the same time the old ties are weakened, and new only outlined.This period is very small.It is a fraction of a second.The result of the collapse of the complex is the formation of the starting materials and products of chemical interaction.
To transitional component arose the need to make the activity of the system.For this need and the activation energy of a chemical reaction.Education transition complex is defined by force, possessed by the molecule.The number of particles in the system depends on the temperature.If it is high enough, the proportion of active molecules is large.The magnitude of the forces of interaction above or equal to the index, referred to as "activation energy".Thus, at sufficiently high temperatures, the number of molecules capable of forming a transition complex high.Consequently, the reaction rate increases.Conversely, if the activation energy is of great importance, the proportion of particles capable of reacting small.
presence of high energy barrier is a barrier to chemical reactions at low temperatures, although the probability exists.Exothermic and endothermic interactions have different characteristics.The first of these occurs with the lowest activation energy and the latter - with most.
used this concept in physics.The activation energy of the semiconductor is the minimum force that must be to accelerate the electrons to move into the conduction band.During this process breaks the bonds between the atoms.In addition, an electron must travel from the valence band to the conduction sector.The increase in temperature is the reason for the gain of thermal movement of particles.In this part of the electron goes into free charge carriers.The internal connections can also be broken by the electric field, light, etc.The activation energy is significantly larger quantities in intrinsic semiconductors compared with the impurity.
