Understanding Electrolytes and Nonelectrolytes
To determine if corn starch is an electrolyte, it is important to understand the difference between electrolytes and nonelectrolytes. An electrolyte, when dissolved in water, breaks apart into free-moving, charged particles known as ions. These mobile ions are essential for conducting an electrical current through the solution. Common examples include table salt (sodium chloride), acids, and bases.
In contrast, a nonelectrolyte dissolves in water but does not produce ions. Instead, its molecules disperse throughout the solution as neutral, uncharged entities. Since there are no mobile charge carriers, the resulting solution cannot conduct electricity. Typical nonelectrolytes include many covalent compounds like sugar (sucrose) and ethanol.
The Chemical Structure of Corn Starch
Corn starch is a carbohydrate, specifically a polysaccharide composed of long-chain polymers of glucose. These polymers are known as amylose and amylopectin, and they are held together by covalent bonds, primarily alpha-glycosidic linkages. Unlike ionic compounds, which are formed by the electrostatic attraction between oppositely charged ions, covalent compounds are formed by the sharing of electrons between atoms.
When corn starch is mixed with water, it does not dissolve completely in cold water but rather forms a suspension of starch granules. Even when heated to the point of gelatinization, the glucose polymers merely swell and disperse rather than breaking down into charged ions. Because the molecular structure remains intact without releasing charged particles, the solution remains a poor conductor of electricity, confirming its status as a nonelectrolyte.
How Electrical Conductivity Works in Solutions
Electrical conductivity in a solution relies on the presence and mobility of charged particles. When an ionic compound like sodium chloride (NaCl) is added to water, the water molecules pull the sodium and chloride ions apart. The liberated $Na^+$ and $Cl^-$ ions can then move freely within the solution. When an electric current is applied, these ions migrate towards the oppositely charged electrodes, completing the electrical circuit.
In a corn starch and water mixture, no such ions are released. The glucose polymer chains, though they may disperse, do not carry a net electrical charge. As a result, they are not attracted to either electrode and cannot facilitate the flow of an electrical current through the solution. This is a clear demonstration of why corn starch, in its natural state, is not an electrolyte. While some research shows that electrical conductivity can be used to monitor cornstarch gelatinization in water, this is due to the slight release of native ions (like potassium and magnesium) within the starch granules and the behavior of the water itself, not the starch polymer acting as an electrolyte.
Can Starch Be Made Conductive?
Interestingly, while pure corn starch is not an electrolyte, it can be modified to become conductive. This is a common practice in the field of materials science, particularly for creating solid polymer electrolytes (SPEs) for applications like batteries and supercapacitors.
One method involves using starch as a host polymer and doping it with ionic salts. For example, studies have shown that adding sodium iodate ($NaIO_3$) or lithium iodide (LiI) to a corn starch film can significantly increase its ionic conductivity. The added salt is the source of the free-moving ions, which are then transported through the polymer matrix.
Furthermore, corn starch has been modified with acids, like citric acid, to produce printable hydrogel-polymer electrolytes for use in printed electronics. This demonstrates that corn starch itself is non-conductive, but its polymer structure can be utilized as a scaffold to create new materials that exhibit electrolyte properties when combined with other, conductive components.
Electrolyte vs. Nonelectrolyte: Key Differences
| Property | Electrolyte | Nonelectrolyte |
|---|---|---|
| Mechanism of Conduction | Dissociates into free-moving ions when dissolved or melted. | Does not dissociate into ions; remains as neutral molecules. |
| Type of Bonding | Primarily ionic bonds (e.g., NaCl, $KNO_3$). | Primarily covalent bonds (e.g., corn starch, sugar, ethanol). |
| Electrical Conductivity | Conducts electricity when in aqueous or molten form. | Does not conduct electricity in aqueous or molten form. |
| Effect on Solution | Increases the conductivity of the solvent significantly. | Has no significant effect on the conductivity of the solvent. |
| Examples | Salts (NaCl), Acids (HCl), Bases (NaOH). | Sugar, Alcohol, Corn Starch, Urea. |
Conclusion
In conclusion, pure corn starch is not an electrolyte because it is a covalently bonded polymer that does not dissociate into free-moving ions when dissolved in water. This lack of mobile, charged particles prevents it from conducting electricity, classifying it as a nonelectrolyte. While it is a non-conductor on its own, corn starch's chemical structure and properties make it a valuable host material in the development of advanced polymer electrolytes when combined with ionic dopants for technological applications. Therefore, for a solution of pure corn starch and water, no electrical conductivity will be observed, reinforcing its nonelectrolyte status. For further exploration of the fundamental differences between these substances, see Study.com's lesson.
