The definitive answer is that solid table sugar (sucrose) does not conduct electricity to any meaningful extent. It is an electrical insulator, a material that strongly resists the flow of electric current. Understanding this requires looking closely at the fundamental conditions necessary for a material to be classified as a conductor.
The Simple Answer: Conductivity Requirements
Electrical conduction requires the movement of charged particles through a material. A substance must satisfy two conditions: it must contain charge carriers (particles with an electrical charge, such as electrons or ions), and these carriers must be mobile, free to move when voltage is applied.
In solid metals, conductivity occurs through the movement of delocalized electrons, known as metallic conduction. In liquids, such as molten salts or salt water, conduction happens through the movement of positive and negative ions, called electrolytic conduction.
Why Sugar’s Covalent Structure Prevents Conduction
Sucrose, a molecular compound, fails to meet either requirement for conduction. The atoms within each sugar molecule are held together by covalent bonds. These bonds involve sharing electrons, but the electrons remain localized and tightly bound within the molecule. This means there are no free electrons available to carry a current, unlike in a metal.
Solid sugar is composed of neutral, uncharged molecules. It does not naturally contain any ions, which are necessary for electrolytic conduction. In its crystalline solid form, these neutral molecules are held in a fixed, rigid structure called a lattice. Their rigid position within the lattice prevents them from moving and carrying a charge.
Any minute electrical activity observed is typically attributed to impurities or a mechanism called protonic conduction. This involves the movement of hydrogen ions through the network of hydrogen bonds linking the sugar molecules. However, this effect is negligible, classifying pure sucrose as an electrical insulator.
Testing the Limits: Sugar in Solution and Melted
The non-conductive nature of sugar remains largely unchanged even when its physical state changes.
Sugar in Solution
When sugar is dissolved in water, the crystal lattice breaks apart, and the individual sucrose molecules separate. Importantly, these molecules remain intact and neutral; they do not break down into charged ions, unlike table salt. Because the resulting sugar water solution contains only neutral molecules, it remains a non-conductor. This is why sugar solution is a non-electrolyte, meaning it does not enhance the water’s ability to carry an electric current.
Melted Sugar
Melting solid sugar also does not introduce conductivity. When heated, the weak intermolecular forces between the neutral molecules break to form a liquid. Since the internal covalent bonds of the molecules remain unbroken, the resulting liquid contains no mobile ions or free electrons and therefore cannot conduct electricity. Sugar only becomes conductive if it is heated to the point of thermal decomposition, where it breaks down and carbonizes, but at that point, it is no longer pure sucrose.