Universal Solvent
The water molecule is "polar," meaning that it has a positively charged pole and a negatively charged pole. The two hydrogen atoms carry a positive charge, and the oxygen atom carries a negative charge. The strength of the electrical charges in the molecule cause its precise shape: water's two hydrogen atoms rest 104.5 degrees apart. The atomic structure of the water molecule attracts other polar and charged molecules, which then dissolves in the water. That is why water it is the universal solvent.
Three States of Matter
Water is the only substance on earth that exists as a solid, liquid and a gas in the earth's natural temperature range. Without this quality we would not have the water cycle and water would not be able to cleanse itself.
Surface Tension
Water may flow freely, but it is very strong. That is, it has a strong surface tension. The molecules on the surface hold together and stretch like an elastic band. Water has the highest surface tension of any liquid on earth except mercury.
Heat Capacity
Water has one of the highest heat capacities on earth. The oceans absorb the sun's heat during the day and release it slowly at night. They keep the earth's temperature relatively stable throughout the 24-hour day. Without the oceans, the planet's temperature would swing hundreds of degrees between night and day.
