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TechnoratiIntermolecular Forces
Submitted by Anonymous on 12 June 2006 - 2:50am.
Hi,
I am doing an experiment on intermolecular forces - Van der Waals, dipole and hydrogen bonds.
The last question with this experiment reads:
"With the same type of agitation and at the same temp. why would sugar dissolve in water much faster the does salt?"
I have read the text several times and can't find the answer.
Water's intermolecular forces are hydrogen bonds- which are strong compared to the rest. So I was thinking perhaps that it is because the surface area of a sugar molecule is greater than that of salt?
Thanks
How *fast* something happens
How *fast* something happens in chemistry is called "kinetics".
It is quite a different question to whether or not something happens at all (which is described by thermodynamics).
Whether or not something will dissolve (ie how soluble it is) is a thermodynamic issue - you are comparing the strength of the bonds before and after it dissolves.
How fast though - that's kinetics............
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A very interesting
A very interesting question!!
If you think carefully about what is happening here you will realise that dissolving sugar leaves the molecule intact and are only breaking forces of attraction between sugar molecules. These are relatively weak.
With the salt you are pulling apart positive and negatively charged ions which are held together by electrostatic attraction. These, by comparison, are much stronger.
It therefore follows that sugar crystals will dissolve faster than salt crystal (under the same conditions). Dissolving salt, if I recall correctly, is also very slightly endothermic.
...pssst...make the sugar
...pssst...make the sugar solution 68% solids w/w and see what happens....OK I will tell...in this instance you are making/learning about super saturated solutions..and at 20 degrees C- 2 % of that sucrose solution will just refuse to dissolve!! Throw that one back at the tutor!!
The rest you have been told by other contributors.
But remember sugar aint always sugar- sucrose is the common sugar, but when you get a chance have a play with glucose ( dextrose),maltose, and other " sugars" to see how they dissolve.