My sister teaches 5th grade science and she recently conducted a classroom exercise where her students dissolved granulated sugar and powdered sugar in water. The granulated sugar went immediately into solution and the powdered sugar made an insoluble, pasty mass.
She asked her chemist brother why this happened.
I suspect that it has something to do with surface tension and particle size.
Any ideas?
Thank you,
Kevin Olsen
Nice question. In a sugar crystal, the molecules stick together well, meaning that they have rather low energy. For a sugar molecule to leave the crystal and go out into the liquid water it has to pick up some energy, because that raises the total energy of the sugar and liquid. What we mean when we say something is "hot" or "high temperature" is that it's easy for its parts to get to high energy. So the hotter the water, the easier it is for a sugar molecule to pick up enough energy to break away from the crystal. So more sugar will dissolve in hot water.
Dear Raveendra,
are you serious or joking?
The answer: the powdered sugar contains a small amount of anti-caking agent.
Dear Sir I am seeing some of the yahoo question and answers and i am answering the question. If any mistake in the answer, sorry for that one.
Yes, powdered sugar (or icing sugar in Europe) is finely divided and covered by starch for preventing its agglomeration in the presence of moisture. It may also contain a small amount of silica for the same role. Hence its very different behaviour, making it valuable in the kitchen for nicely icing cakes ...
Alain
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