11Jan_3 - Biological Science I Tuesdays and Thursdays...

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Biological Science I Tuesdays and Thursdays 8:00-9:15, HCB 102 Mondays 5:15-6:15, KIN 1024 11 January 2010 – Lecture 3 WATER – THE MEDIUM OF LIFE Water: appears to be unique to our earth covers three-fourths of its surface constitutes 60-70 wt % of the living world regenerates and is redistributed through evaporation (water cycle) exists in all three states (ice, water, steam) in the natural environment absolutely essential to life (dehydration kills quickly) Develop our understanding of water on three fronts: II. Hydrogen Bonding III. Emergent properties IV. Acid Base chemistry I. Hydrogen Bonding A. The structure of water is simple – you must be able to draw water A.1. One O covalently bonded to two H A.2. Bond angle is 105 O A.3. O is electronegative – it attracts electrons. A.4. The electrons of the H spend more time closer to the O A.5. Unequal electron distribution gives water a polarity A.5.a. O region is ha a slight “-” charge A.5.b. H ends have a slight “+” charge B. The polar nature allows for interactions B.1. Liquid B.1.a. Fragile disorganized hydrogen bonds B.1.b. Last few trillionths of a second B.1.c. Constantly reforming B.2. Solid B.2.a. Organized hydrogen bonds – four neighbors in 3D space B.2.b. Crystal is more spacious than disorganized liquid – Ice floats B.3. Gas B.3.a. Single molecules liberated from others by the addition of energy 1
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Biological Science I Tuesdays and Thursdays 8:00-9:15, HCB 102 Mondays 5:15-6:15, KIN 1024 11 January 2010 – Lecture 3 II. Emergent properties that make water great for sustaining life on earth A. Cohesion, adhesion, and surface tension A.1. Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion A.2. Cohesion helps the transport of water against gravity in plants A.3. Adhesion is an attraction between different substances, for example, between water and plant cell walls A.4. Surface tension is a measure of how hard it is to break the surface of a liquid - Surface tension is related to cohesion B. Ability to moderate temperature B.1. Heat and Temperature B.1.a. Water absorbs heat from warmer air and releases stored heat to cooler air B.1.b. Water can absorb or release a large amount of heat with only a slight change in its own temperature B.1.c. The behavior of water is the basis for the metric temperature scale B.1.c.a. The Celsius scale is a measure of temperature using Celsius degrees (°C) B.1.c.b. A calorie (cal) is the amount of heat required to raise the temperature of 1 g of water by 1°C B.1.c.c. The “calories” on food packages are actually kilocalories (kcal), where 1 kcal = 1,000 cal
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11Jan_3 - Biological Science I Tuesdays and Thursdays...

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