The Importance of Water as a Medium for Life

The Importance of Water as a Medium for Life
Water is a very important liquid found on the Earth?s surface and makes up 60 to 90 % of the fresh mass of all living things and is very important for cells. It is also an important habitat for animals such as fish and other aquatic organisms. It consists of 2 hydrogen atoms, covalently bonded to an oxygen atom. When discussing what makes water such an important medium for life, I must consider properties, such as its dipolar charge, its ability as a solvent, its thermal properties, its density, its high surface tension and its cohesion. An important feature of water is that it has a dipolar (uneven) charge. This occurs because of the covalent bonds shared between the 2 hydrogens and the oxygen atoms. When these covalent bonds are formed, the oxygen nucleus attracts electrons more then the hydrogen nuclei do, due to oxygen having 8 protons opposed to hydrogen?s 1 proton.
The result of this is that oxygen has a slight negative charge (δ-), and hydrogen having a slight positive charge (δ+). Water is an excellent solvent and has an ability to dissolve many polar substances in it. This is caused by water molecules (dipolar molecules) being attracted to polar molecules, surrounding them and separating them, making them dissolve. These dissolved chemicals are then free to move around and can then react with other chemicals. It is for this reason that biochemical reactions occur so effectively in living organisms, since living cells have a cytoplasm based in solution. Water molecules are attracted to one another by hydrogen bonds, restricting the movement of the particles. It is for this reason that water requires a relatively large quantity of energy to increase its temperature. Consequently, water is slow to change temperature in areas of high water content. This is useful in living organisms as it makes keeping a stable body temperature easier, being able to avoid rapid temperature changes and helping reactions in the body to take place at a narrow range in temperature. Another benefit of water?s thermal properties is that it needs a very high amount of energy to evaporate it into a gas (100� c boiling point). This makes sweating very effective for cooling the body. In contrast to this, water also needs a high amount of energy to be transferred away from it to make it freeze. This is important in making sure that living organisms, particularly aquatic creatures don?t freeze up. An unusual property of water compared with many other liquids is that its solid form (ice) is a lot less dense than its liquid form. We know this because ice tends to float on top of water. As this occurs in ponds and streams, the ice that forms on top of water insulates the liquid below it, ensuring that life beneath the ice survives. This is an important property of water, which ensures that aquatic animals don?t have their environment constantly fluctuating at different temperatures. The water temperature stays practically the same all year round. It is very rare to find large quantities of water completely freezing, even in extreme weather conditions. Since water molecules are attracted to one another by hydrogen bonds, they tend to stick together. This is illustrated well when water is sucked through a straw. The hydrogen bonds which attract other water molecules towards them make it possible for the water to flow. A way in which this property of water is used, is when plants absorb water through the long unbroken columns in their xylem tissues. This property in water is called cohesion and makes water an important transport medium in animals and plants. This cohesion in water molecules generates what is known as surface tension, meaning a thin smooth layer on the top of water. This enables small creatures such as pond skaters to use water as an environment. I feel that water is very important as a medium for life. This is due to many important properties that it holds. One of these properties is a dipolar charge, which causes hydrogen bonds to attract to each other and cause cohesion, which is important for transport. Another important property is the fact that it is an excellent solvent. This means that many biochemical reactions are able to take place in water, which is why 60 to 90% of the fresh mass of living things are made up of H2O. Water is also good for its thermal properties which insulate the bodies of living organisms, making it easy for them to keep a constant temperature. Another unusual property is that the density of water decreases when it?s a solid, which protects the organisms in lakes and ponds in extreme weather conditions. Each of these properties make water a very important substance for living in, whether we need it as an environment, to whether we need it for biochemical reactions in or bodies to take place. In conclusion, without water, the earth would be a very inhabitable place to live in for living organisms.

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