Dissertation on Water
The Chemical and Physical Properties of Water
Millions of years ago the first forms of life on Earth originated in the oceans. Today, although many plants and animals live on land, they are still dependent on water. Though odourless, transparent, and not very exciting to the taste buds, this life sustaining liquid is perhaps the most important liquid in the world. Covering 75% of the Earth's surface it serves as many purposes which would not be possible if it were not for its specific physical and chemical properties, those of which I will be discussing.
Water consists of two volumes of hydrogen to one volume of oxygen. The hydrogen atoms are arranged at a bonding angle of 105 degrees. This makes the water molecule polar because the shape of the molecule is such that it has a positive end and a negative end. This polarity accounts for the strong bonding between the molecules and peculiar properties of water, e.g. Relatively high melting and boiling point, expands when freezes. Because of its polarity water is a good solvent, attracting both the positive and negative charges of other solutions. This is very important because all chemical reactions in cells take place in aqueous solution.
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Water has a pH of 7, which makes it a neutral liquid medium. It's neutrality ensures that reactions taking place within living organisms are not disturbed by being too acidic or basic. Blood in animals and sap in plants consist largely of water. It's serves as a transport medium for food and removal waste materials within living organisms. Water is transparent allowing for sunlight to penetrate deep into water bodies. If it were not, photosynthesis would not take place and few organisms would be able to survive. Transparency also allows for organisms to see in water.
Water has a high specific heat, meaning that it takes large amounts of energy to cause a change in temperature. Because so much energy is needed to raise or lower the temperature, oceans and other bodies of water remain at a relatively constant temperature, ensuring that the organisms that they house are provided with a constant environmental temperature. The same is true for organisms living on land. A constant body temperature is crucial because rates of chemical reactions are greatly affected by temperature. Water also helps minimise temperature fluctuations. Without this property, living organisms would overheat or freeze to death with the slightest change in temperature.
Along with high specific heat water also has a high heat of vaporisation. This property is important because it allows for perspiration in humans and transpiration in plants to take place. Without these cooling processes taking place, living organisms would overheat. The amount of heat man produces in one day would be enough to raise his body temperature to 150 degrees Celsius if it were not for the water present in his body.
Water molecules have a high surface tension, because of the molecules very strong tendency to stick to each other (cohesiveness). This results in water molecules at the surface to crowd together and produce a strong layer, providing a habitat for certain aquatic organisms. The strong cohesive forces also play an important part in the movement of water up the vessels and tracheids of plants. If these forces were weaker, trees would not grown as tall.
The fact that water is less dense as a solid than a liquid is very important. As a result ice floats in water. If the opposite occurred and ice sank in water, frozen water in a lake or ocean would sink to the bottom and pile up to the top, killing all the marine life. The expansion of water when it freezes has important geological effects. Water that enters tiny cracks in rocks creates an enormous amount of pressure when it freezes, expands and then splits or breaks the rock, playing a great part in erosion.
The importance of water as a medium for life springs from its abundance on the Earth's surface. Water is the major constituent of living matter. Seventy percent of our total body weight is water. As ice it is found as glaciers, snow, hail and frost. It occurs in liquid form as dew, rain, in swamps, rivers and oceans. As gas it occurs as fog, steam and clouds. If it were not for the specific properties that allow for water to be so abundant, life on Earth would not exist.
Water has a high specific heat, meaning that it takes large amounts of energy to cause a change in temperature. Because so much energy is needed to raise or lower the temperature, oceans and other bodies of water remain at a relatively constant temperature, ensuring that the organisms that they house are provided with a constant environmental temperature. The same is true for organisms living on land. A constant body temperature is crucial because rates of chemical reactions are greatly affected by temperature. Water also helps minimise temperature fluctuations. Without this property, living organisms would overheat or freeze to death with the slightest change in temperature.
Along with high specific heat water also has a high heat of vaporisation. This property is important because it allows for perspiration in humans and transpiration in plants to take place. Without these cooling processes taking place, living organisms would overheat. The amount of heat man produces in one day would be enough to raise his body temperature to 150 degrees Celsius if it were not for the water present in his body.
Water molecules have a high surface tension, because of the molecules very strong tendency to stick to each other (cohesiveness). This results in water molecules at the surface to crowd together and produce a strong layer, providing a habitat for certain aquatic organisms. The strong cohesive forces also play an important part in the movement of water up the vessels and tracheids of plants. If these forces were weaker, trees would not grown as tall.
The fact that water is less dense as a solid than a liquid is very important. As a result ice floats in water. If the opposite occurred and ice sank in water, frozen water in a lake or ocean would sink to the bottom and pile up to the top, killing all the marine life. The expansion of water when it freezes has important geological effects. Water that enters tiny cracks in rocks creates an enormous amount of pressure when it freezes, expands and then splits or breaks the rock, playing a great part in erosion.
The importance of water as a medium for life springs from its abundance on the Earth's surface. Water is the major constituent of living matter. Seventy percent of our total body weight is water. As ice it is found as glaciers, snow, hail and frost. It occurs in liquid form as dew, rain, in swamps, rivers and oceans. As gas it occurs as fog, steam and clouds. If it were not for the specific properties that allow for water to be so abundant, life on Earth would not exist.
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