Water is a very unique and important liquid. It is the reason for the survival of life on this planet. It is essential for all living things. Water is often referred to a universal solvent because of its ability to dissolve many substances. The reason for all of these special properties has to do with the way individual water molecules are able to interact with each other. To understand the reasons that make waters properties so important, you first need to understand waters molecular behavior.
Cohesion and Adhesion
Water is attracted to other water. This is called cohesion. The cohesive forces are especially strong on the surface of water and form surface tension. When water is not attracted to any other substance it will stick to itself trying to take as little amount of surface area as it can creating a sphere shape (bead). Water can also be attracted to other materials. This is called adhesion. Adhesion forces are stronger than cohesion forces meaning when water has the chance to stick to other substances it is attracted to it will. For example on glass water will not stay together because the adhesion forces the water has with the glass are greater than the cohesive forces causing the water to spread out on a thin film.
Nearby water molecules are attracted to each other. The reason why the surface tension is so great at the surface of water is because there are fewer water molecules and so they have a greater attraction to the few molecules nearby. This causes the surface area of water slightly harder to break than the interior. Two creatures that really take advantage of this are the Basilisk lizard and the Water Strider. The basilisk can't actually stay suspended on the water but in fact it runs fast enough along the water before the surface tension breaks. The Water Strider's tinny mass and the geometry of its legs allow it to be supported by the surface tension.
Capillary action is related to the adhesive properties of water. You can easily see an example of this when you place a straw in a glass of water. The water in the glass tries to climb up the straw. This is because the water molecules are attracted to those of the straw. Because the water molecules are still slightly attracted to each other the molecule attached to that of the straw will pull up the other water molecule creating this capillary action. The water in the straw can only climb so far until the forces of gravity become greater causing the molecules to drop once again. Plants really take advantage of this. The roots of the plants pull in the water and the water molecules from there will climb up the stem of the plant. You can also see this on the outside of a glass of water. You can see that on the edges of the glass the water molecules will curve upwards sticking to the glass. This is called the meniscus.
High Specific Heat
Water has a very high specific heat of 4.186 joule/gram C. It has a higher specific heat than any known substance. Water plays a very important part in temperature regulation. A really good example of this is how when you put water on an oven to boil the oven may be hot, but it will take time for you to feel the same amount of heat coming from the water.