What does the "proof" mean on a bottle of liquor? i know that 100 proof liquor is 50% alocohol and 80 proof is 40% and so on. but where does the term "proof" come from and why display it on the bottle? why not just say 50% alcohol etc etc?

Different isotopes indicate that an element will have different numbers of

Which of the following ocean acidification? are the most likely side effects of a ph less than 7.0 in the ocean b. more metal salts altering the ocean chemistry c. dissolution of the shells of marine organisms d. both a & b e. all of the above.

Chromosome 17 is made of over million base pairs.