WJEC AS Biology - Biological Molecules - Water

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Water

 (http://www.ethicalsuperstore.com/blog/wp-content/uploads/2011/05/water-art-4.jpg)

Water is a polar molecule and has an no overall charge. The oxygen end of the molecule has a slight negative charge and the hydrogen end of the molecules has a slight positive charge. When two water molecules are in close contact their opposing charges attract each other forming a hydrogen bond. Individually hydrogen bonds are weak but because there are many of them they stick together in a strong lattice frame work. This sticking together of water molecules is called cohesion. This means that tall columns of water can be drawn up xylem vessels in tall trees.

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At ordinary temperatures water has the highest surface tension of any liquid except mercury. In a pond cohesion between water molecules produces surface tension so that the body of an insect such as the pond skater is supported.

 (http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/graphics/water.gif)

 Water is a solvent. Because water is a polar molecule it will attract other charged particles, such as ions, and other

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