The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the ...

Show the animation Conservation of Mass in Physical and Chemical Changes. Explain that whether a process involves melting, dissolving, or a chemical reaction, all the atoms that were there before the ...

Photo: Seabamirum [CC by 2.0]/Flickr. Extinction is a natural part of evolution, having already claimed an estimated 99 percent of all species in Earth's history.