Animation showing the interactions between water molecules, and then water and ethanol (alcohol) molecules. Water and ethanol are completely miscible due to these interactions. In the first part of the clip, the water molecules are seen to form transient hydrogen bonds (black) with other water molecules. This is due to interactions between parts of the molecules with a slight negative charge (red) and positive charge (blue). The property of having a slight separation of charge in a molecule is known as polarity. When ethanol molecules are added, the same occurs: hydrogen bonds form between the polar OH groups on the ethanol and the polar water. The non-polar two-carbon chain of the ethanol (green) does not get in the way of this interaction, and the ethanol is completely soluble in water. See clip K004/5586 for a mixture of water and hexane, showing their immiscibility, and K004/5378 for the miscible mixture of ethanol and hexane.