Re: Why is milk heavier than water?

Hi Robyn

The answer is quite simple really. Milk is water with stuff dissolved in it. So there are more bits in the same amount of space, if you know what I mean. If not, take a glass of water and weigh it, now weigh out some table salt (not more than half the volume of the glass preferably). Add this salt to the glass and stir - this makes the water cloudy. You should notice that as you stir, the water goes from cloudy to clear. Magic! the salt has disappeared! But wait... weigh the glass again and it should weigh the same as it did before plus the weight of the salt you added. The salt has just dissolved. Now leave the glass for a sibling to drink :).

Dissolving is the process by which liquids surround other substances. Water is a good solvent because it is polar (ie the charge on the H2O molecule has positive and negative areas) and so other charged ions or polar molecules can be surrounded by H20 molecules as opposite charges attract. -Things tend to dissolve because this increases entropy, which the universe seems to like. If you want to understand this better (as i’m sure my half-assed explanation isn’t too good) look up dissolving in any chemistry textbook. Entropy can be found in physics books under thermodynamics.

Anyway as I understand it, milk also contains cells, proteins, amino acids, fatty acids and minerals such as calcium and sodium. These are all somehow dissolved in water and so make up Milk, as a result it is heavier than the same volume of pure water. Those are also what make milk good for you, so keep drinking it ;-)

Paul Henderson