General Biology Lecture 1 Notes

General Biology Lecture 1 Notes - General Biology Lecture...

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General Biology Lecture Notes Hydrogen Bonds Relatively weak bonds Form when A hydrogen atom with a partial positive charge (e.g. in water) Is attracted to an atom (usually O or N) with a partial negative charge( e.g. in Ammonia) Each atom is already bonded to another molecule or part of the same particle. Van der Waals interactions Based on fluctuating electric charges: Similar molecules, compounds in constant motion o Set up a region w/ temporary excess or deficit of electrons e.g. millions of separate water molecules In these regions, adjacent molecules may be attracted to each other over short distances Weak forces from temp bonding in larger Cohesion and Adhesion Water molecules exhibit cohesion – form hydrogen bonds with one another (stick to each other ) Water molecules exhibit adhesion – hydrogen bonding to other substances with ionic/polar regions A combination of adhesion and cohesion accounts for capillary action even against the force of gravity (e.g. water up a plant stem) Cohesion: Each H2O molecule can form H bonds with a maximum of 4 neighboring water molecules. Fig 2-13 Specific Heat Hydrogen bonding is also responsible for waters high specific heat o Amount of energy required to raise the temp of water is quite high. Hydrogen bonds must be broken to raise the water temp o Specific heat of water is 1 cal/g of water/degree C, which is far higher than ethyl alcohol which is 0.59 cal/g/degree C. High heat input needed to raise the water temp- means that the oceans and large bodies of water are quite constant in temperature. Specific heat of water helps organisms maintain relatively constant internal temperature. General Biology Lecture Notes September 17, 2009 Heat of Vaporization Water has high heat of vaporization o The amount of heat required to change 1g of water from liquid to vapor o Measured as calories 1 cal = heat energy required to raise temp of 1g water, 1 degree C Hydrogen bonds must also break for molecules to enter vapor phase o To vaporize water one needs 540 cal because of the hydrogen bonding Evaporative Cooling When water is heated, some molecules escape as vapor and carry heat with them, lowering temp of the liquid causing evaporative cooling
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This note was uploaded on 01/18/2012 for the course BIO 101 taught by Professor Martin during the Fall '08 term at Rutgers.

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General Biology Lecture 1 Notes - General Biology Lecture...

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