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Chapter 3

Chapter 3. Water and the Environment. The Molecule That Supports All of Life. Can exist in 3 forms at once Main reason Earth is habitable Life on earth probably evolved in water Living organisms require water more than any other substance Most cells are surrounded by water

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Chapter 3

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  1. Chapter 3 Water and the Environment

  2. The Molecule That Supports All of Life • Can exist in 3 forms at once • Main reason Earth is habitable • Life on earth probably evolved in water • Living organisms require water more than any other substance • Most cells are surrounded by water • Cells are compose of 70–95% water

  3. The polarity of water results in hydrogen bonds • polar molecule • Oxygen very electronegative • Attractions exist between partially charged poles

  4. Emergent properties of water contribute to life on Earth • Properties of water that support life: • Cohesive and Adhesive • Ability to moderate temperature • Solid form lighter than liquid form • Versatility as a solvent

  5. Cohesion • Water molecules tend to stick to each other • Surface tension

  6. Adhesion • Water molecules stick to other polar molecules • Counteracts gravity

  7. Moderation of Temperature • Heat is transferable energy • Objects exchange heat until they are achieve an equal temperature • Water has a high heat capacity • Absorbs/releases great amounts of heat

  8. Heat is a form of energy and temperature is a measure of the kinetic energy of an object or solution • Heat energy increases the movement of molecules • Water has high specific heat • Can absorb and release great amounts of heat, influencing the temperature

  9. Water has a high heat of vaporization • Evaporative cooling

  10. Water Expands when it freezes • Ice floats in liquid water • Hydrogen bonds are more “ordered,” making ice less dense • Floating ice insulates bodies of water

  11. Water is the solvent of life • Solution • Solvent • Solute • Aqueous solution

  12. Hydrophilic substances • Hydrophobic substances Hydrogen Shell Salt, an ionic compound, dissociates in water

  13. (b) Lysozyme molecule (purple) in an aqueous environment (c) Ionic and polar regions on the protein’s surface attract water molecules. (a) Lysozyme molecule in a nonaqueous environment • Even large polar molecules such as proteins can dissolve in water but maybe not completely

  14. Acids and Bases • Changes in hydrogen ion concentration results in acidic and basic solutions • Measured as pH

  15. Acid • substance that increases H+ of a solution • Base • substance that reduces H+ of a solution • Salt • substance that has no impact on H+ of a solution

  16. pH calculated by: • pH = -log [H+] • For a neutral solution • [H+] is 10–7 = –(–7) = 7 • Each number represents a tenfold difference in ion concentrations

  17. Buffers • Buffers • minimize changes in H+ and OH– concentration • accept or donate H+ to maintain consistent pH • pH of living cells maintained close to 7

  18. Blood always contains a combination of some carbonic acid and some bicarbonate ions. When hydrogen ions (H+) are added to blood: When hydroxide ions (OH−) are added to blood: Prevents any significant change in blood pH

  19. Threats to Earth’s Water Quality Acid Precipitation Reduction of CO32- in Oceans

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