So this is the last part of the article I'm publishing as a serial. And I will talk about chemistry. In particular, I'm going to show you something about Avogadro, a very powerful program. By the way, did you know that this program takes its name from the italian chemist/physicist Amedeo Avogadro (http://en.wikipedia.org/wiki/Amedeo_Avogadro), best known for the definition of the "mole" concept with his follower Stanislao Cannizzaro? Basically, the mole is a unit to describe the number of objects you have. For example, having a mole of molecules means you have 6,022*10^23 molecules. And having a mole of books means you have 6,022*10^23 books. This number is now called "the Avogadro number", in honour to the scientist.
Add a dimension to chemistry
Avogadro is one of the best programs to draw molecules in three dimensions. This program, anyway, can do a lot more: it has handy tools to build complex molecules, and gives you some informations about what you have drawn. There is another interesting program (that I will not describe since it's very easy to use): Kalzium. This one is very useful for its "calculators": these are some little tools allowing us to do some simple calculations (concentration of a soluzion, mass of a compound, etc...). There is also a wonderful chemical equation solver, and a "reader" of risk and security phrases. If you are just starting to learn chemistry, there is also a good glossay, that will show you the main laboratory tools and explain some practices.