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The water cycle.

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Introduction

Water covers 70% of the earth's surface and is vital to all living things. Water is always circulating between the earth's surface and the atmosphere in the water cycle. Many processes work together to keep the Earth's water moving in a cycle. There are five processes at work in the hydrologic cycle: 1. Condensation Condensation is the process of water changing from a vapour to a liquid. Water vapour in the air rises mostly by convection. This means that warm, humid air will rise, while cooler air will flow downward. As the warmer air rises, the water vapour will lose energy, causing its temperature to drop. The water vapour then has a change of state into liquid or ice. 2. Precipitation Precipitation is water being released from clouds as rain, sleet, snow, or hail. Precipitation begins after water vapour, which has condensed in the atmosphere, becomes too heavy to remain in atmospheric air currents and falls. 3. Infiltration A portion of the precipitation that reaches the Earth's surface seeps into the ground through the process called infiltration. ...read more.

Middle

Explanation 2 Heat from the sun makes water evaporate from the oceans, rivers and lakes forming water vapour. As the water vapour rises it cools and starts to condense and become water again. This forms clouds. As the clouds get cooler the water droplets become bigger and bigger. Eventually they fall as rain, snow, sleet, or hail. The water then runs back into the oceans, rivers and lakes and the cycle repeats! Water is the lifeblood of industry. It is used as a raw material, a coolant, a solvent, a transport agent, and as a source of energy. A regular sized family car coming off the assembly line, for example, will have used at least 120 000 litres of water - 80 000 to produce its tonne of steel and 40 000 more for the actual fabrication process. Many thousands more litres of water are involved in the manufacture of its plastic, glass, fabric components. Manufacturing accounted for 14% of water withdrawals in 1996. ...read more.

Conclusion

The greatest part of the hard water is built by hydrogen carbonates. You measure the water hardness in "DEUTSCHEN H�RTEGRADEN" (�dH) � Water: 0 -7 �dH > is soft water � Water: 8 -15 �dH > is middle-hard water � Water: more than 15�dH > is hard water Temporary hardness can simply be removed by boiling the water. Permanent hardness can be removed by adding sodium carbonate. Hard water contains dissolved compounds which are good for health. It often provides calcium to strengthen bones, and there is evidence of people who live in hard water areas as they have reduced risk of heart disease. Using hard water can increase cost as more soap is needed. Some hard water decomposes when it is boiled. Ca(HCO3)2 � CaCO3 + H2O + CO2 This is the reverse of the reaction which forms the hard water in the first place. Water will dissolve a little bit of most things, but the polar nature of the water molecule results in water molecules orienting themselves around charged particles making ions and polar molecules the most soluble. This is why it is used as a solvent. ...read more.

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