Question: how many molecules are in 1 cup of water?
Answer: The density of water is 1 gram per cc, so 1 mole of water takes 18cc of volume. 1 cup is approximately 250ml (i.e. 250cc) - so 1 cup will contain approximately 13.89 moles of water, which will contain approximately 8.36 x 1024 molecules of water.