[constant thinker]

To demonstrate the powerful dehydrating effects of concentrated sulfuric acid, add some concentrated sulfuric acid (~98% is what I used) to some sugar. The reaction takes a few seconds at room temperature. When it's all said and done with your left with carbon that has been liberated of H and O.

---!Caution!---
This should be done outside seeing as when I did it, I got some SO₂ that came off it. Also concentrated acids are not to be screwed around with. I spilt some on a wooden table and it caused a nice sized hole in the table. Ask many of the people here (especially Limpet Chicken) about their experiences with concentrated acids.

[mike]

The dehydration of sugar is rather exothermic (ie the container and contents will get very hot). The equation fo the reaction is:

C₁₂H₂₂O₁₁ (s) + 11H₂SO₄ (l) -----> 12C (s) + 11(H₂SO₄.H₂O) + lots of heat

So you will most likely get steam and sulfuric acid fuming out of the flask so this is best done in a hood. Do not stand over the reaction or inhale the vapour.