Page 19 - Curriculum Visions Dynamic Book

Sulphuric acid dehydrates sugars
If sulphuric acid is added to sugar (sucrose) the sugar dehydrates, that is, it loses its water and turns into black carbon.
The reaction produces considerable heat,
so water is released as steam. The chemical equation shows that the sulphuric acid remains uncombined. As the steam is given off, bubbles form, which cause the carbon to develop into a “volcano” of a substance which, on cooling, has the feel of coke.
 As the glucose is dehydrated it changes to black carbon. At this stage the glucose is a hot, syrupy liquid, which does not readily allow the steam to escape, so some of it remains trapped as bubbles.
dehydration: the removal of water from a substance by heating it, placing it in a dry atmosphere, or through the action of a drying agent.
glucose: the most common of the natural sugars. It occurs as the polymer known as cellulose, the fibre in plants. Starch is also a form of glucose. The breakdown of glucose provides the energy that animals need for life.
oxidation: a reaction in which the oxidising agent removes electrons. (Note that oxidising agents do not have to contain oxygen.)
EQUATION: Dehydration of sucrose
 The expanding bubbles
are trapped in the carbon as the reaction finishes and the carbon cools to a coke-like hard material.
Sucrose + sulphuric acid ➪ water + carbon + sulphuric acid C12H22O11(s) + H2SO4(aq) ➪ 11H2O(g) + 12C(s) + H2SO4(aq)
19
19