2 basic Law of chemistry

Conservation of mass law and law of definite proportions

Antoine Lavoisier (1743-1794)
Conservation of mass law
"mass of a closed system (in the sense of a completely isolated system) will remain constant over time"

Antoine Lavoisier , French chemist,Antoine Laurent Lavoisier was born on August 26, 1743, in Paris.

Lavoisier's experiments were among the first truly quantitative chemical experiments ever performed. He showed that, although matter changes its state in a chemical reaction, the quantity of matter is the same at the end as at the beginning of every chemical reaction. These experiments provided evidence for the law of the conservation of matter. Lavoisier also investigated the composition of water, and he named the components of water oxygen and hydrogen.


Joseph Proust (1754-1826)
law of definite proportions
"chemical compound consists of elements by comparison mass which is always exactly the same"

French chemist. Joseph Louis Proust was born in Angers and educated in Paris. He is best known for establishing the chemical law of definite proportions, sometimes called Proust's law, which states that the elements in a compound are all present in a fixed proportion by weight, regardless of how the compound is prepared.

Proust studied copper carbonate, the two tin oxides, and the two iron sulfides to prove this law. He did this by making artificial copper carbonate and comparing it to natural copper carbonate. With this he showed that each had the same proportion of weights between the three elements involved (Cu, C, O). Between the two types of the other compounds, Proust showed that no intermediate indeterminate compounds exist between them

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History of name Atomism in philosophy

The word atom derives from the ancient Greek adjective atomos, which literally meant 'uncuttable' (a - tomos (not cuttable) – tomos a conjugate of the Greek verb temnein (to cut)).

The word atom is understood in primarily two distinct ways:

firstly, by the physical sciences;

secondly, by philosophy.

Early time name Atomism is traditionally associated with philosophy,, in the fifth century BC:
Leucippus and his student Democritus proposed Atoms are the smallest possible division of matter, do not have physical parts, and cannot be split, cut nor in any way further divided; they are either sizeless (point-sized) or they have a tiny size , in order to reconcile two conflicting schools of thought on the nature of reality. On one side was
Heraclitus,
who believed that the nature of all existence is change. On the other side was
Parmenides,
who believed instead that all change is illusion.
Two fundamental and opposite theorized atom consists of two fundamental and opposite:
-indivisible bodies – atoms
-void

Democritus accepted most of Parmenides' arguments, except for the idea that change is an illusion. He believed change was real, and if it was not then at least the illusion had to be explained. He thus supported the concept of void, and stated that the universe is made up of many Parmenidean entities that move around in the void.The void is infinite and provides the space in which the atoms can pack or scatter differently. The different possible packings and scatterings within the void make up the shifting outlines and bulk of the objects that organisms feel, see, eat, hear, smell, and taste. While organisms may feel hot or cold, hot and cold actually have no real existence. They are simply sensations produced in organisms by the different packings and scatterings of the atoms in the void that compose the object that organisms sense as being "hot" or "cold."
The work of Democritus only survives in secondhand reports, some of which are unreliable or conflicting. Much of the best evidence of Democritus' theory of atomism is reported by Aristotle in his discussions of Democritus' and Plato's contrasting views on the types of indivisibles composing the natural world.

In other side
Aristotle
Sometime before 330 BC asserted that the elements of fire, air, earth, and water were not made of atoms, but were continuous. Aristotle considered the existence of a void, which was required by atomic theories, to violate physical principles. Change took place not by the rearrangement of atoms to make new structures, but by transformation of matter from what it was in potential to a new actuality. (This theory is called hylomorphism.) A piece of wet clay, when acted upon by a potter, takes on its potential to be an actual drinking mug. Aristotle has often been criticized for rejecting atomism, but in ancient Greece the atomic theories of Democritus remained "pure speculations, incapable of being put to any experimental test. Granted that atomism was, in the long run, to prove far more fruitful than any qualitative theory of matter, in the short run the theory that Aristotle proposed must have seemed in some respects more promising.

source:http://en.wikipedia.org/wiki/Atomism

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