6
votes
5answers
859 views

Nano-particle or Molecule?

What's the difference between something being labeled a "nano-particle" or it being called a "molecule"?
9
votes
3answers
3k views

What determines the color of a pure substance and is it possible to predict it?

I have always wondered why salt is white, water is clear and gold is, well, gold. What determines the color of a substance? Does it have something to do with the electrons? And is it possible to ...