Sugar (a carbohydrate) is dehydrated with concentrated sulfuric acid. Since a carbohydrate was once considered just hydrated carbon, if you remove the water, carbon would be left over. The acid rips the water out of the sugar and the heat generated by this reaction causes the water to turn to steam. A black mass of carbon is produced.
1. Place the sugar into the beaker 2.
2. Add the sulphuric acid to the beaker
3. Stir it briefly.
4. Wash the carbon column in excess water to dilute and wash away the acid.
The sucrose turns yellow and then red brown. After about one and a half minute the mixture changes color to black and a spongy mass of carbon grows well above the top of the cylinder. The formation of a carbon column is accompanied by the release of heat and evolution of vapor.