Why doesn't salt water and fresh water mix?

Answer 1

Salt water and fresh water do mix, when you mix them the salt water becomes more dilute meaning there is slightly more water then salt then there was before. If you want to witness them mixing for yourself, the experiment you could do is quite simple. Just take salt water and dye it one color and take fresh water and dye it another. Then just pour the contents of both into a glass, stir and wait a few hours. You'll find that the salt water which is dyed the one color does not separate from the fresh water which you dyed another. Salt water and fresh water are really just two types of the same thing, the only difference between the two is the type of impurities present. Those impurities defuse into purified or fresh water as easily as cigarette smoke diffuses into the air.

Answer 2

It will mix a bit, but the salt in the sea water makes the sea water heavier, causing it to pool below the fresh water.

Haven't done this experiment, but I'd bet that given a month the separation of the waters will be gone. (Water disolves in water.)

Answer 3

They do mix. Salt water and fresh water are not two completely different things; salt water is just fresh water with salt dissolved in it. Any time the two solutions are in contact, a saline gradient will form along initial boundary. Over time the gradient will become less steep, and eventually the system will reach equilibrium and the entire solution will be a less concentrated salt water.

Under certain conditions, it can appear as if they are not mixing, such as if there is a constant source of fresh water running into the ocean. At areas near the source it will appear as though the water nearer the source is not mixing, but this is just because more unmixed solution is being added.

There are places in the sea where there is a layer of water high in salt below a layer of water which is low in salt, and there can seem to be a pretty distinct boundary between them. However, if you stopped the currents from flowing, the two bodies would readily mix.

Answer 4

It does, but possibly only slowly through diffusion. The saltwater, containing various solutes, is heavier than pure water and displaces it, staying at the bottom. Sometimes rain will make the top section of salt ponds brackish (only slightly salty) without disturbing the concentrated salt solution farther below.

Answer 5

What makes you think they don't? They mix quite easily.