Chapter 5

Chapter 5 - Intro to Oceanography: Chapter 5 I. Why does...

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Intro to Oceanography : Chapter 5 I. Why does Water Have Such Unusual Chemical Properties? a. Atomic Structure i. Atoms are the basic building blocks of all matter. ii. Oxygen + Hydrogen -> Water 1. Oxygen a. 8 protons and 8 electrons 2. Hydrogen a. 1 proton iii. An atom will lose or gain one or more electrons and thus have an overall electrical charge (ions) b. The Water Molecule i. A group of two or more atoms held together by mutually shared electrons 1. Geometry a. Oxygen is twice the size of hydrogen b. Central oxygen covalently bonded to two hydrogen atoms separated by and angle of 105 degrees c. Relatively strong chemical bonds, so a lot of energy is required to break them d. Instead of straight line, there is a bend (both hydrogen atoms are on the same side of the oxygen atom) 2. Polarity a. Bent geometry gives a slight negative charge to the side of the oxygen atom and a slight positive charge to the side of the hydrogen atroms b. Gives it a dipolar polarity 3. Interconnections of Molecules a. Hydrogen bond formed when positively charged hydrogen area interacts with negatively charged oxygen area b. Water molecules stick together exhibiting cohesion c. Surface tension – thin “skin” that allows a glass to be filled just above the brim without spilling any of the water 4. Water: The Universal Solvent a. The electrostatic attraction between oppositely charged ions produces an ionic bond b. Hydration – process by which water molecules completely surround ions II. What Other Important Properties Does Water Possess? a. Water’s Thermal Properties i. Heat, Temperature, and Changes of State 1. Attractive forces – hydrogen bonds and van de Waals forces
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2. Energy must be added to the molecules or ions so they can move fast enough to overcome these attractions 3. Heat a. Energy of moving molecules b. Proportional to the energy level of molecules and thus is the total kinetic energy of a substance c. Calorie – amount of heat required to raise the temperature of 1 gram of water by 1 degree centigrade 4. Temperature a. Direct measure of the average kinetic energy of the molecules that make up a substance ii. Water’s Freezing and Boiling Points 1. melting point – if enough energy is added to a solid 2. freezing point – if enough energy is removed from a liquid 3. boiling point – if enough energy is added to a liquid 4. condensation point – if enough energy is removed from a gas 5. Pure water melting and freezing occur at 0 º C 6. Pure water boiling and condensation occur at 100 º C iii. Water’s Heat Capacity 1. Heat Capacity – the amount of heat required to raise the temperature of 1 gram of any substance by 1 degree centigrade 2. Water’s heat capacity is exactly 1 calorie per gram iv. Water’s Latent Heats 1. When water undergoes a change of state, the amount of heat absorbed or released is due to water’s high latent (hidden) heats
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This note was uploaded on 04/05/2008 for the course ES 15 taught by Professor Schauble during the Fall '06 term at UCLA.

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Chapter 5 - Intro to Oceanography: Chapter 5 I. Why does...

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