Here's why:

* Water molecules: Water (H₂O) is composed of two hydrogen atoms and one oxygen atom. These atoms are connected by covalent bonds, which are strong and share electrons.

* Hydrogen bonds: Water molecules are polar, meaning they have a slightly positive end (near the hydrogens) and a slightly negative end (near the oxygen). This polarity allows water molecules to form weak bonds called hydrogen bonds with each other. These bonds are weaker than covalent bonds, but they are still important.

* Life-supporting properties: The unique properties of water that support life are largely due to the hydrogen bonds between water molecules:

* High heat capacity: Water can absorb a lot of heat energy before its temperature increases significantly. This helps to regulate the temperature of organisms and the environment.

* High heat of vaporization: Water requires a lot of energy to change from a liquid to a gas (evaporation). This helps organisms cool down through sweating.

* Excellent solvent: Water's polarity allows it to dissolve many substances, making it an ideal medium for chemical reactions in living organisms.

* Cohesion and adhesion: Hydrogen bonds give water its cohesive (stick together) and adhesive (stick to other surfaces) properties. This allows water to move through plants and animals.

* Density: Water is less dense as a solid (ice) than as a liquid. This means ice floats, which is essential for aquatic life.

In summary, water's ability to form hydrogen bonds is the key to its unique properties that make it essential for life.