Debating the concept of the atom - the planet's smallest molecular unit - can be traced all the way back to Ancient Greece, when philosophers and scholars that took place around the sixth century B.C. One of the questions that interested these thinkers was the nature of matter. Is matter, they asked, continuous or discontinuous? That is, if you could break apart a piece of chalk as long as you wanted, would you ever reach a point where division was impossible? Or could you keep up that process of division forever? An important role in this concept was the philosopher Democritus, who named those particles atoms. In Greek, "atomos" means "indivisible." .
In the early 19th century, english schoolteacher John Dalton came up with an explanation for the different laws of mass and proportions. His concept can be summed up by theses few statements: .
1. All matter is composed of extremely small particles called atoms.
2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ .
in size, mass, and other properties.
3. Atoms cannot be subdivided, created, or destroyed.
4.Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged.
Daltons atomic theory explains that the Law of Conservation of Mass is due to chemical reactions involving just the combination, separation, or rearrangement of atoms while during the process they are not created nor destroyed. An example of an experiment testing this would be one done by French chemist Antoine-Laurent Lavoisier in the early 1700's. "Lavoisier heated mercury in the retort (pictured below) for several days until its whole surface was covered with red particles. During this process, the air in the bell jar diminished in volume. He found that the air remaining in the ball jar could no longer support either life or combustion.
