Expire Worthless is when options enter expiration out of the money and expire without any remaining value. Expiring worthless is one of the most common terms used in options trading. Options expire worthless whenever they go into expiration out of the money.
A single molecule of water consists of three atoms. H2O is built from a single atom of oxygen that is single-bonded with two atoms of hydrogen.
A mole is a convenient counting unit whenever one is dealing with numbers of atoms or molecules. It is equal to Avogadro's number (NA), namely 6.022 x10 23. If we have one mole of water, then we know that it will have a mass of 2 grams (for 2 moles of H atoms) + 16 grams (for one mole O atom) = 18 grams. Since we only have 0.001 grams, that means that we have NA * (0.001/18) = 3.35*10 19 molecules of water!