Hydrocarbon fuels do not mix with water.

• A. They dissolve in water
• B. They emulsify in water
• C. They mix readily with water
• D. They do not mix with water

Answer: (D)

Hydrocarbon fuels do not mix with water because of polarity differences and the resulting immiscibility of nonpolar and polar liquids. Water is highly polar and forms strong hydrogen bonds, while hydrocarbons are nonpolar and interact mainly through weak London dispersion forces. This mismatch means hydrocarbons cannot be solvated by water, so they separate into distinct layers rather than dissolving or mixing uniformly.

Dissolving would require the hydrocarbon molecules to be carried into the water by favorable interactions, which doesn’t happen here. Emulsifying would require surfactants or agitation to stabilize dispersed droplets; in pure form, hydrocarbons don’t form a stable emulsion in water. Mixing readily would imply easy, complete blending, which isn’t the case for immiscible liquids. Therefore, the statement that hydrocarbons do not mix with water best describes their behavior.