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Cellular Chemistry (2)

Cellular Chemistry (2). Unit 2. THE PERIODIC TABLE. Water. All living organisms are mostly water, and all chemical reactions of life are carried out in water Hydrogen bonds between water molecules give water unique properties that make life possible Capacity to dissolve many substances

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Cellular Chemistry (2)

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  1. Cellular Chemistry (2) Unit 2

  2. THE PERIODIC TABLE

  3. Water • All living organisms are mostly water, and all chemical reactions of life are carried out in water • Hydrogen bonds between water molecules give water unique properties that make life possible • Capacity to dissolve many substances • Cohesion (surface tension) • Temperature stability

  4. Polarity and the Unique Properties of Water

  5. Water and Solutions • Polar water molecules hydrogen-bond to other polar (hydrophilic) substances, and repel nonpolar (hydrophobic) substances • Hydrophilic (water-loving) • A substance that dissolves easily in water • Hydrophobic (water-dreading) • A substance that resists dissolving in water

  6. Water and Solutions • Water is an excellent solvent • Solvent • Liquid that can dissolve other substances • Solute • A dissolved substance

  7. Water and Solutions • Salts, sugars, and many polar molecules dissolve easily in water • Salt • Compound that dissolves easily in water and releases ions other than H+ and OH- • Example: sodium chloride (NaCl)

  8. Water and Solutions Water molecules surround the atoms of an ionic solid and pull them apart, dissolving it

  9. Temperature Stability • Temperature stability is an important part of homeostasis • Water absorbs more heat than other liquids before temperature rises • Hydrogen bonds hold ice together in a rigid pattern that makes ice float • Temperature • Measure of molecular motion

  10. Cohesion • Cohesion helps sustain multi-celled bodies and resists evaporation • Cohesion • Tendency of water molecules to stick together • Evaporation • Transition of liquid to gas • Absorbs heat energy (cooling effect)

  11. Acids and Bases • Water molecules separate into hydrogen ions (H+) and hydroxide ions (OH-) • pH • A measure of the number of hydrogen ions (H+) in a solution • The more hydrogen ions, the lower the pH • Pure water has neutral pH (pH=7) • Number of H+ ions = OH- ions

  12. Acids and Bases • Acid • Substance that releases hydrogen ions in water • pH less than 7 • Base • Substance that releases hydroxide ions (accepts hydrogen ions) in water • pH greater than 7

  13. A pH Scale

  14. Acid Rain Sulfur dioxide and other airborne pollutants dissolve in water vapor to form acid rain

  15. Buffer Systems • Most molecules of life work only within a narrow range of pH – essential for homeostasis • Buffers keep solutions in cells and tissues within a consistent range of pH • Buffer • Set of chemicals that can keep the pH of a solution stable by alternately donating and accepting ions that contribute to pH

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