is sugar a pure substance?

Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. 

Sources and Kinds

Sugars are found in the tissues of most plants. Honey and fruits are abundant natural sources of simple sugars. Sucrose is especially concentrated in sugarcane and sugar beet, making them ideal for efficient commercial extraction to make refined sugar. In 2016, the combined world production of those two crops was about two billion tonnes. Maltose may be produced by malting grain. Lactose is the only sugar that cannot be extracted from plants. It can only be found in milk, including human breast milk, and in some dairy products. A cheap source of sugar is corn syrup, industrially produced by converting corn starch into sugars, such as maltose, fructose, and glucose.

Pure substance

Sugar is a pure substance. But sugar is a word used loosely for many types of sugars. Chemically, sugars are either monosaccharides like glucose and fructose or disaccharides like sucrose which is generally referred as sugar. Whether it is derived from cane or beetroot, it is purified into crystalline form and therefore it can be called pure. Larger the size of crystal the purer is the material. Thus amorphous and powdery products may contain impurities.

Uses

Sugar is used in prepared foods (e.g. cookies and cakes), is sometimes added to commercially available ultra-processed food and beverages, and may be used by people as a sweetener for foods (e.g. toast and cereal) and beverages (e.g. coffee and tea). 

Raw sugar manufacture

Sugarcane processing is practiced in many variations, but the essential process consists of the following steps: extraction of the cane juice by milling or diffusion, clarification of the juice, concentration of the juice to syrup by evaporation, crystallization of sugar from the syrup, and separation and drying of the crystals.