Question

why the sugar get black by evaporating water

Answer 1

Good Evening!

The sugars ,glucose, sucrose and fructose all are carbon based molecules. As one heats any of the sugars, the hydrogen and oxygen molecules will break their bonds and be released into the atmosphere. This leaves behind carbon which will darken the residue from brownish to black as more carbon is liberated. There is a point in caramelization when the flavor changes from sweet to bitter to burnt. This is due to the change in molecular structure from application heat.

Answer 2

sugar is made up of carbon and water vapour. on evaporating the water vapour escapes from sugar and merges with the atmosphere leaving carbon behind. since carbon is black in colour the sugar gets black by evaporating water.