Learn more physics!
Q:
Can you get fresh water from salt water by evaporation. If yes,how?
- Anonymous (age 12)
A:
Sure -- that's a process known as "distillation", although evaporation
is only half of the story. Evaporation from salt water gives nice, pure
water vapor, but to produce water again requires condensation. This can
be done by flowing the water vapor (+ any air it might be mixed with)
past a surface that is cooler than it, and necessarily cooler than the
boiling point of water. The cooler it is, the faster it will condense
water out of the vapor. The condensing surface is tilted so the water
that forms runs down the surface into a container. If the condensing
surface is colder than 32 degrees Fahrenheit (0 Celsius) some water
will freeze on the condensing surface.
Note -- the salt from the seawater (and anything else that might
have been in it) stays in the original container holding the seawater.
Eventually this may cake up with salt and it will have to be cleaned
out. Some people buy sea salt at the grocery store and claim it is
tastier than the kind you get out of salt mines (I cannot tell the
difference however).
Tom
(published on 10/22/2007)
Follow-Up #1: Biblical water
Q:
I hear and read that the water supply in the area Jesus taught was polluted and scarce so the people drank wine. Did the inhabitants of that area know how to produce clean water from brackish water and saltwater?
- Bob Sims (age 67)
Huntsville, Alabama, USA
Follow-up on this answer.
