Bio 1201 Chapter 3 -

Bio 1201 Chapter 3 - - Chapter 3 Water and the Fitness of...

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Chapter 3 Water and the Fitness of the Environment Water: Hydrogen Bonding, Solubility, and Specific Heat - 3.1.1 Cells are 70-95% water. Water cover 70% of the earth’s surface. I. Some of the most biologically important polar covalent bonds are the bonds in water molecules. A. Because of these polar covalent bonds water is a polar molecule . 1. This is an example of an emergent property. 2. Polar covalent bonds are when the sharing of electrons is not equal 3. The polarity of water molecules makes water a good solvent for molecules that have charged regions (polar molecules) or atoms that are charged (ions) 4. Water is a very versatile solvent (see fig. 3.6 and fig 3.7). *Solution – a liquid that is homogenous mixture of two or more substances Solvent – liquid in which substances are dissolved Solute – the dissolved substance *Aqueous solution – when something is mixed/dissolved in water II . Interaction is based on change either partially charged or fully charged Atoms ability to pull electrons – electronegativity <- they both want some # of electrons so pull is same Example: Carbon: outershell is 4/8 full Hydrogen: outershell is ½ full Oxygen: valence shell is 6/8 full – more electronegative than ^ Nitrogen: valence shell is 5/8 full – more electronegative because bigger A. Water's polarity along with hydrogen bonding orders water into a higher level of structural order (see fig. 3.2).
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Because oxygen has a higher electronegativity, it pulls more electrons from the hydrogen molecules B. This higher structural order and polarity results in some other extraordinary emergent properties: 1. Water has a high specific heat making it resist changes in temperature This helps to moderate the effects of changes in temperature. 2. Heat is the kinetic energy due to molecular motion in matter
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This note was uploaded on 03/19/2010 for the course BIOL 1201 taught by Professor Wishtichusen during the Fall '07 term at LSU.

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Bio 1201 Chapter 3 - - Chapter 3 Water and the Fitness of...

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