can someone briefly explain what did aristotle and what did plato contribute to chemistry?

Answer 1

It is hard to characterize it.

Aristotle effectively put Democritus' ideas of the atom and divisible matter on hold for a thousand years. Aristotle believed in the four elements (fire, water, air, earth), and that chemical reactions occured when these were disrupted. Plato, his student, modified these to suggest that chemical reactions occured when certain geometric shapes were to fit
http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html

These ideas stuck around through time, and it was not until Robert Boyle debunked them were we able to start to advance atomic theory and chemistry again.

So if you want to call these "contributions", you may.

Answer 2

Plato was a philosopher/mathematician/ teacher/ etc. You can read about him and his relationship to Socrates, Aristotle, and others, at the first link below. I don't know that he contributed any thing scientifically based to chemistry; however, he was a deep thinker and contributed greatly to the learning process. The second link gives some discussion on Aristotle.

http://en.wikipedia.org/wiki/Plato

http://www.historyworld.net/wrldhis/PlainTextHistories.asp?historyid=ac20

Answer 3

Both, Aristotle and Plato believed that matter could be subdivided indefinitely into smaller and smaller parts. In other words, they did not believe in indivisible units or atoms. Their contribution to chemistry was that they thought about, and discussed the ultimate structure of matter.
Other ancient Greek philosophers did promote the idea of atomic structure of matter but they were not as famous as Aristotle. That delayed the acceptance of the atomic theory of matter until the beginning of the 19th century.