Substances that are not soluble in polar solvents like water but dissolve in nonpolar solvents are typically classified as what?

• A. Carbohydrates
• B. Lipids
• C. Proteins
• D. Nucleic acids

Answer: (B)

Substances that don’t mix with water but dissolve in nonpolar solvents are hydrophobic by nature. Lipids fit this pattern because they are built mostly from long hydrocarbon chains and other nonpolar components. Water is highly polar and forms strong hydrogen bonds, which don’t interact well with those nonpolar regions, so lipids don’t dissolve in water. However, nonpolar solvents like hexane or chloroform can dissolve lipids through favorable nonpolar interactions, so they do dissolve there. In contrast, carbohydrates, proteins, and nucleic acids contain many polar or charged groups that interact readily with water, making them soluble in polar solvents rather than nonpolar ones. This is why lipids are the best classification for substances insoluble in water but soluble in nonpolar solvents.