Question

Why is ethanol able to mix with both water and gasoline (octane) but gasoline and water do not mix?

Answer 1

Hydrogen bonding

Explanation:

Ethanol can undergo hydrogen bonding, "Any molecule which has a hydrogen atom attached directly to an oxygen or a nitrogen is capable of hydrogen bonding. Such molecules will always have higher boiling points than similarly sized molecules which don't have an -O-H or an -N-H group." (https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Intermolecular_Forces/Specific_Interactions/Hydrogen_Bonding)

H-Bonding allows water and the OH group of ethanol to bond together, so they can mix, Gasoline is a hydrocarbon, with no OH group attached, therefore cannot undergo H-Bonding, and cannot mix with water.