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W16
Making salt, sugar
and citric acid visible again = crystallisation
Salt, sugar and citric acid
cannot have been lost during the previous experiment.
Now it will be observed how the 3 solutions change while the liquid disappears.
Material
The
3 solutions of the previous experiment.
Experiment
In the previous experiment the grains
of salt, sugar and citric acid disappeared during mixing with 3 big drops. They
were dissolved (Photo 1).
F* Halte den Tropfen
--> Leave the solution for
evaporation of the water..
Observation
The 3 white solids are visible again:
Salt forms small cubes, citric acid
reappears as small fans, sugar does not (yet) show a special shape (Photo
2).
Explanation
After their dissolution the invisible
particles of the 3 solids are mixed with so many small particles of water that
they remain separated from each other. Later on more and more water particles
left the liquid and mixed with air. Finally the remaining water could no longer
separate the particles of salt sugar and citric acid. The particles of different
substances have different shapes and properties. So each substance forms a solid
of typical shape called crystal. Photo
3 and 4: Crystals of salt and of sugar (rock candy).
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publication: 11.09.2001
................................last
modification: 21.12.2008