Final answer:
Three examples of chemical changes in white sugar (sucrose) include oxidation, the reducing action of sugars, and dehydration reactions. These demonstrate the transformation of sugar molecules into new substances, like the charring of sugar into carbon, the reduction of metal salts, and the formation of new bonds through the removal of water.
Step-by-step explanation:
Chemical changes involving white sugar, specifically sucrose, can occur through various reactions. Three types of these chemical changes are:
- Oxidation: Sucrose can be oxidized when heated over a flame, leading to its charring and the formation of a blackened mixture primarily consisting of carbon. This demonstrates a chemical change as sucrose is converted into new substances.
- Reducing action: In an alkaline medium, sucrose and other sugars such as glucose and fructose can reduce certain metal salts (like copper) due to their aldehydic or ketonic groups. For instance, Benedict's reagent is used to detect reducing sugars in urine.
- Dehydration reaction: Disaccharides like sucrose can undergo dehydration reactions, where water is removed from the sugar molecule, often in the formation of glycosidic bonds between monosaccharides.
Sugars can be further classified based on the presence of aldehydic or ketonic groups.
For example, glucose, galactose, and fructose are all hexoses with the same molecular formula, but they differ in structure determining whether they are an aldose or a ketose.
The type of glycosidic bond, whether it's an alpha or beta bond, also plays a role in the sugars' chemical behavior, as in the case of maltose and lactose.