Tuesday, 5 May 2015

Chemical Energy

Chemical energy

The chemical energy is an energy that varies due to the formation or breaking of chemical bonds of any type in the chemical elements involved in chemical reactions.

Since the strength of the chemical bonds is associated with the distance between the chemical species (in fact stronger chemical bonds held closer to the chemical species involved in binding), the chemical energy depends on the mutual position of the particles that constitute a substance.

It is then the energy stored in the chemical bonds and is mainly due to the sum of the potential energy of electrostatic interactions of the charges in the ponderable matter, most of the kinetic energy of the electrons.

If you consider as "zero level" of chemical energy that where there are no chemical bonds, chemical energy is negative. Ties have several different binding energy, the more stable have more negative value.

Resonance is a phenomenon chemical structure that greatly influences the chemical energy in a stabilizing way. The reactivity and kinetics of the various compounds suffer from differences of chemical energy.

The chemical energy is produced in the course of the transformations that take place at the molecular level.

The chemical energy introduced into our bodies with food, for example, allows us to live through oxidation and in general cell metabolism (cellular respiration).

Abu Abdullah Mahammad Jabir ibn Al-batani

He, like Qurra Thabit was born in Harran and also his family belonged to the sect of Sabian. But it is believed that the name "Allah Abu Muhammad" indicates that Al-Battani, unlike Thabit Qurra, was of the Islamic faith. So, a younger generation of Thabit. 

It is not inconceivable that the two are popular. He began his career as an astronomical observer (and manufacturer of astronomical instruments) in the Syrian town of Ar-Raqqah and Antioch. Is there a document (Fihrist, "Index"), the century X, certifying the highest level of fame he was gratified in his time both for the quality of his astronomical observations for his works. According to this Fihrist he observed between the years 877 and 918, while his star catalog is the year 880. His works are listed in Fihrist Kitab al-Zij and a commentary on Tetrabiblos Ptolemy.

The Kitab al-Zij is his most important work. It includes 57 chapters and covers topics will happen according to the classical scheme of Zij introduction of mathematical, astronomical theory, tables. Let's see in brief what were the most important results achieved by Al-Battani. He gave a catalog of 489 stars. He perfected the assessment of the duration of the year to 365 days, 5 hours, 48 ​​minutes, 24 seconds. Gave to the precession of the equinoxes the annual value of 54 ".5 and 23; 35 'for the obliquity of the ecliptic.

 Ascertained the progression of solar longitude of the apogee and the possibility of having annular eclipse of the sun. Some But the authority of Ptolemy at the time of Al-Battani was so great that, despite his calculations he had been made to determine the distance of the Sun is deviated greatly from that established by Ptolemy, did not dare to say so publicly. Where instead manifested with clearly their challenge to Ptolemy was the Ptolemaic method of determining the apparent diameter of the Moon: al-Battani states that the Moon can have an apparent diameter smaller than that of the Sun, which explains why they occur annular eclipses. 
He says then that same solar diameter can vary, contrary to what claimed Ptolemy. Commentators agree that the importance of Al-Battani in the development of science manifested itself especially in the influence that his work had on scientists such as Copernicus, Brahe and Galileo .

Using very precise instruments for the time, made a revision of astronomical constants listed in the Almagest, correcting them and discovering the movement solar apogee