Science homework my son is stuck on.?

I am stuck on a desert island with nothing to drink but seawater. I need to in some way separate the salt so that I am able to drink the water. How should I do this and why?

Please help. He has tried answering this question but is a little stuck. Any help and scientific explanations would be extremely helpful and I would be grateful...thank you.....

Answer:
Humans cannot drink saline water. But, saline water can be made into freshwater, which everyone needs everyday. The process is called desalination, and it is being used more and more around the world to provide people with needed freshwater.
In nature, this basic process is responsible for the hydrologic cycle. The sun causes water to evaporate from surface sources such as lakes, oceans, and streams. The water vapor eventually comes in contact with cooler air, where it re-condenses to form dew or rain. This process can be imitated artificially, and more rapidly than in nature, using alternative sources of heating and cooling.

You could achieve the same result by causing evaporation of the seawater though heat (hot sunshine will do!) followed by condensation of the resultant steam (the technical term is vapour-compression distillation), while the salt will precipitate as a solid waste.

You can have a look at the device to use in this page:
http://ga.water.usgs.gov/edu/drinkseawat...
I remember this from school to seperate salt from water you need to use a filtering device. The reason that he can't drink the salt water is because salt causes you to feel even more thirsty and people have died from having only salt water. Best wishes!
Ella B
Sea water composes of water and salt.
The boiling point of water is much lower than of salt.
By heating the solution (water and salt) up, water will boil first giving steams, by collecting steam and condense it gives water.
Hmm what kind of equipment does he have with him. He can either heat the sea water so that it evaporates into a separate contained plus giving you salt and pure water, or by the means of some filter device
make a hole in the sand and make onther hole put the water through the sand wil filter the water oh ya make a connetion for both of them and put some stones inside
You would use distillation to purify the water. Several references are given. You would create a still similar to the way they did things on Gilligan's Island. It can be done with native things using the sun as the heat source. Filtration of salt requires power and large equipment to do, so on an island it could not occur.
Distillation would be the best way.
use a simple distillation unit .u can get it from any chemical store near by
You cannot remove salt from water by filtration because the salt also goes through the filter holes just as easily as the water. That is what we mean when something is dissolved. Sand will not filter the salt out. The technological answers like distillation and reverse osmosis are fine if you have the equipment. But you don't say you have the equipment or anything to make it with. So they are out.

The only answer is to move inland, presuming the island is reasonably large. Then dig a well. Fresh water from rain is less dense than salt water and with a matrix of sand around it, will float on the salt water without mixing, at the top, anyway. I hope the island is sandy or well digging could be difficult without a spade.
i think you'll need a container for the water to evaporate there.
first thing you need to do is to heat the sea water and the water would evaporate. you should connect a container on the other end so you could get pure water. this process is distillation..ΓΌ

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