Caramelization or caramelisation (see spelling differences) is the oxidation of sugar, a process used extensively in cooking for the resulting nutty flavor and brown color.
As the process occurs, volatile chemicals are released, producing the characteristic caramel flavor. If a sucrose solution is left in a sand bath over night, the sucrose (once the water has evaporated) will caramelize.
When caramelization involves sucrose, it adds one water molecule to sucrose to split it apart to form fructose and glucose, increasing the mass of the sugar (caramel).