Question: how many water molecules are in 1 ml of water?
Answer: In this case, a density of `1.00 g/mL tells you that every milliliter of water has a mass of 1.00 g . Finally, the relationship between number of moles and number of molecules is given by Avogadro's number, which tells you that every mole of a substance contains exactly 6.022⋅2023 molecules of that substance.