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WATER AND THE FITNESS OF THE ENVIRONMENT CHAPTER 3

WATER AND THE FITNESS OF THE ENVIRONMENT CHAPTER 3. I. The Effects of Water’s Polarity. A. The _______ of water molecules results in _________ bonding. 1. Two hydrogens form ________ covalent bonds with an oxygen.

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WATER AND THE FITNESS OF THE ENVIRONMENT CHAPTER 3

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  1. WATER AND THE FITNESS OF THE ENVIRONMENT CHAPTER 3

  2. I. The Effects of Water’s Polarity

  3. A. The _______ of water moleculesresults in _________ bonding • 1. Two hydrogens form ________ covalent bonds with an oxygen. • Because oxygen is more ____________, the region around oxygen has a partial negative charge. • The region near the two hydrogen atoms has a partial positive charge. • 2. Water is a polar molecule with opposite ends having opposite charges.

  4. B. The Unique Properties of Water: • 1.Water molecules stick to each other, a phenomenon called ____________. --Cohesion plays a key role in the _________ of water against _________ in plants. • 2. ___________,water sticks to other stuff, contributes too, as water adheres to the wall of the vessels.

  5. 3. _________________ of water is very high because of hydrogen bonding at the surface.

  6. 4. Water moderates ___________ on Earth • Water can absorb or release relatively large amounts of heat with only a slight change in its own temperature because it has a high specific heat. • Water stabilizes air temperatures by absorbing heat from warmer air and releasing heat to cooler air. • Water has a high heat of vaporization which allows for evaporative cooling.( The molecules with the most kinetic energy leave as a gas).

  7. 5. Oceans and lakes don’t freeze solid because ice ________. • Water is unusual because it is less ________ as a solid than as a liquid. • Most materials contract as they solidify, but water expands. • At temperatures above 4oC, water behaves like other liquids, expanding when it warms and contracting when it cools.

  8. 6. Water is the solvent of life • A liquid that is a completely homogeneous mixture of two or more substances is called a __________. • A sugar cube in a glass of water will eventually dissolve to form a uniform mixture of sugar and water. • The dissolving agent is the _______ and the substance that is dissolved is the ________. • In our example, water is the solvent and sugar the solute. • In an _______ solution, water is the solvent. • Water is considered the universal polar solvent.

  9. a. Water is an effective solvent because it forms hydrogen bonds with charged molecules. • For example, when a crystal of salt (NaCl) is placed in water, the Na+ cations form hydrogen bonds with partial negative oxygen regions of water molecules. • The Cl- anions form hydrogen bonds with the partial positive hydrogen regions of water molecules.

  10. Each dissolved ion is surrounded by a sphere of water molecules, called a ____________shell. • Eventually, water dissolves all the ions, resulting in a solution with two solutes, sodium and chloride. Hydration shells

  11. b. Any substance that has an affinity for water is ___________or “water loving.” • These substances are dominated by ionic or polar bonds. • This term includes substances that do not dissolve because their molecules are too large and too tightly held together. • For example, cotton is hydrophilic because it has numerous polar covalent bonds in cellulose, which is its major constituent.

  12. c. Substances that have no affinity for water are __________ or “water fearing.” • These substances are dominated by non-ionic and nonpolar covalent bonds. • Because there are no consistent regions with partial or full charges, water molecules cannot form hydrogen bonds with these molecules. • Oils are hydrophobic because the dominant bonds, carbon-carbon and carbon-hydrogen, exhibit equal or near equal sharing of electrons. • Hydrophobic molecules are the major ingredients of cell membranes.

  13. II. The Dissociation of Water • A.Water molecules dissociate and a hydrogen ion is transferred to a second water molecule creating a __________ion (H3O+). • B.The water molecule that lost it’s proton is called a _________ion (OH) -.

  14. C. Acids and Bases • 1. ________ are substances that _______the relative number of H+ ions in solution. • For example: HCl = H+ + Cl • 2. _______are substances that ________ therelativenumber of H+ ions in solution. • For example: NaOH = Na+ + OH- • A base may also reduce the number of H+ directly by capturing the H+ ions: • NH3 + H + NH4+

  15. D. _______ minimize changes in pH • They ______ H+ when the solution is acidic and _________ H+ ions when the solution becomes basic. • Blood pH is 7.4(slightly basic). A change to 7.0 or 7.8 is deadly! • Carbonic acid dissociates to yield a bicarbonate ion and a hydrogen ion: H2CO3 HCO3- + H+

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