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TGK2:
Separating a solution of salt in water
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Evaporation video
Students should notice that the water evaporates to leave
the salt: none of the salt particles leave. This tells us
that it is very difficult for salt particles to leave the
mixture.
Distillation video
The amount of water collected is only 10ml. We show a better
method for distillation in ‘A closer look at boiling’.
Forming crystals
Here the salt crystals form because the volume of water is
going down: the remaining solution cannot keep all the salt
dissolved. This is different from using a change in solubility
with temperature to grow crystals, when the volume of water
remained the same. Notice that the salt crystals are much
smaller when they are made to form quickly.
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Science Enhancement Programme CD-ROM 2005 |
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user
guide |
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