Video narration
Why doesn't ethanol settle into a separate layer when you pour it into a glass of water? At the molecular level, ethanol has an O-H group that attracts nearby water molecules. The O-H groups form hydrogen bonds-intermolecular attractions, not new chemical bonds. These ethanol-water attractions replace some water-water attractions, so molecules spread throughout the mixture. Ethanol's small carbon part doesn't stop this. So ethanol is miscible with water: it mixes completely, rather than sitting as a separate layer.