Water

Water
Water Water has 2 very important roles! But anyway, without water no life would exist on earth, it is the most important biochemical of all. Three quarters of the earth is covered with water. 1.Role 70-95% percent of a cell contains water. The human body for example contains about 60% water. 2.Role An environment for all organisms, which live in water. Such a small molecule would exist as a gas at normal Earth temperatures were it not for its special property of hydrogen bonding to other water molecules. In water (used as a medium) molecules and ions can mix in and hence a medium. In this medium life could envolve. Hydrogen Bonds are hard to break and hard to convert from liquid standard to a gas. Therefore a lot of energy is needed. Because of this qualitys, it is difficult to separate the water molecules and to affect the physical properties of water.
Important other roles Water as a solvent Water is a solvent for ions and polar molecules. Water has the quality, that its molecules are attracted to ions and polar molecules and can collect around and separate them. Chemicals can move free and react with other chemicals in water. Most processes in living organisms take place in solution in this way. As soon as a chemical dissolves in water, the watermolecules start doing the mentioned process. But, water is not a solvent for non-polar molecules and lipids. In contrast, the water molecules start pushing them together, until the water molecules are attracted to each other. Because of this, the structures are more stabile and it is important in hydrophobic interactions in protein and membrane structure. Water as a transport medium The fact that water is an solvent is very important in other areas, too. In animals it is needed, to transport things in the blood, in the lymphatic, in the excretory and in the digestive systems. In plant cells it is needed as a tranport medium in the vascular tissues. Properties of water Thermal properties But the fact, that hydrogen bonds are hard to break, is not only good. A lot of energy is needed, to move the water molecules and so to raise the temperature of water. But anyway, that?s not so bad, because it makes water more stabile. For example if in summer the temperature of an ocean raises, the water won?t get cold in the winter very fast. Another example is the human body, which contains about 60% water. The water in the human body, or rather the water molecules in the water, makes the body temperature more stabile and make it harder to change the temperature. Another advantage for the human body and for the living organisms in water is, that water doesn?t freeze so fast. Because a lot of energy is needed, to change water into a gas, during the progress of evaporation a lot of energy is transfered. This can be an effective mean of cooling the body, for example, when it is hot and you?re sweating. But, also a lot of energy must be transferred from water, before it is changed from a liquid to a solid. Density and freezing properties Water is not like other chemicals, the solid form is less dense than the liquid form. Below 4 C the density of water starts to decrease. In this process, the ice is ?swimming? on the water and insulates the water under it. So the advantage is, that big bodies of water doesn?t freeze completely and organisms, who live in the water have a bigger chance to survive in the winter. High surface tension and cohesion Another quality and important property of the water molecules is, that they tend to stick to each other. This ?function? is useful, because water moves in long, unbroken columns through the vascular tissues in a plant. There are a lot of little organisms, for example the pond skater, which can ?walk? on the water surface. The reason, why they are able to do that, is that the high cohesion also results in high surface tension at the surface of water. Glaciers and icecaps: A storehouse of fresh water Almost 10% of the world?s land mass is currently covered with glaciers, mostly in places like Greenland and Antarctica. Glaciers begin their life as snowflakes. When the snowfall in an area far exceeds the melting that occurs during summer, glaciers start to form. The weight of the accumulated snow compresses the fallen snow into ice. These ?rivers? of ice are very heavy, and if they are on land that has a downhill slope the whole ice patch starts to slowly slide downhill. The size of glaciers varies, some are as big as a football-field, some are as bis as a river a hundred meters long. If all glaciers melted today the seas would rise about 260 feet. Water withdrawals e.g. United States in 1995 Public supply (water delivered to our homes and businesses by water departments) Domestic (water use at home) Irrigation (water for growing crops, golf courses, etc.) Thermoelectric power (electrical-power generation, other than hydroelectric) Livestock (water for cows, chickens, horses, etc.) Hydroelectric power (power produced at dams) Wastewater treatment (sewage treatment)

Water 8.5 of 10 on the basis of 1592 Review.