Hydrogen Bond
Many of water's unique properties arise because of a phenomena called Hydrogen Bonding. Hydrogen bonding arises because water is a polar molecule. But what does this mean?
Water carries no overall charge, but, as the diagram to the left shows, Oxygen atoms contain many electrons and they all surround it nucleus. The positive nucleus is completely surrounded by negative electrons. What's more it has 'extra' electrons that it is sharing with Hydrogen. The Oxygen is said to be electronegative. By contrast, the Hydrogen atoms have just one electron each and that is drawn towards the Oxygen leaving the positive nucleus exposed. We say it is electropositive.
As with all instances involving charges, opposites attract. The attraction between the partial positive charge of the Hydrogen and the partial negative charge of an adjacent Oxygen is called Hydrogen bonding. Hydrogen bonds are individually weak, but collectively strong.
Water carries no overall charge, but, as the diagram to the left shows, Oxygen atoms contain many electrons and they all surround it nucleus. The positive nucleus is completely surrounded by negative electrons. What's more it has 'extra' electrons that it is sharing with Hydrogen. The Oxygen is said to be electronegative. By contrast, the Hydrogen atoms have just one electron each and that is drawn towards the Oxygen leaving the positive nucleus exposed. We say it is electropositive.
As with all instances involving charges, opposites attract. The attraction between the partial positive charge of the Hydrogen and the partial negative charge of an adjacent Oxygen is called Hydrogen bonding. Hydrogen bonds are individually weak, but collectively strong.
This video explains this a little more, as well as some of the following properties that make water essential to life.