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Chemistry of Life

Explore the chemistry of water and its special properties such as cohesion, adhesion, high specific heat, and heat of vaporization. Learn why water is essential for life and how it plays a crucial role in sustaining ecosystems.

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Chemistry of Life

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Presentation Transcript

  1. Chemistry of Life Properties of Water

  2. More about Water Why are we studying water? All life occurs in water • inside & outside the cell

  3. Chemistry of water • H2O molecules form H-bonds with each other • + attracted to – • creates a sticky molecule

  4. Elixir of Life • Special properties of water • cohesion & adhesion • surface tension, capillary action • good solvent • many molecules dissolve in H2O • hydrophilic vs. hydrophobic • lower density as a solid • ice floats! • high specific heat • water stores heat • high heat of vaporization • heats & cools slowly I like the partabout the ice!

  5. Cohesion & Adhesion • H bonding between H2O molecules is cohesion • water is “sticky” • surface tension • drinking straw • H bonding between H2O & other substances is adhesion • capillary action • meniscus • water climbs uppaper towel or cloth Can you sucksugar up a straw?

  6. How does H2O get to top of trees? Transpiration built on cohesion & adhesion Let’s go to the videotape!

  7. Water is the solvent of life • Polarity makes H2O a good solvent • polar H2O molecules surround + & –ions • solvents dissolve solutes creating solutions

  8. Do you dissolve in water? • Hydrophilic • substances have attraction to H2O • polar or non-polar?

  9. Or don’t you? • Hydrophobic • substances that don’t have an attraction to H2O • polar or non-polar? fat (triglycerol)

  10. The special case of ice • Most (all?) substances are more dense when they are solid, but Not water… • Ice floats! • H bonds form a crystal And this hasmade all the difference!

  11. Ice floats

  12. Why is “ice floats” important? • Oceans & lakes don’t freeze solid • surface ice insulates water below • allowing life to survive the winter • if ice sank… • ponds, lakes & even oceans would freeze solid • in summer, only upper few inches would thaw • seasonal turnover of lakes • cycling nutrients in autumn

  13. Specific heat • H2O resists changes in temperature • high specific heat • takes a lot to heat it up • takes a lot to cool it down • H2O moderates temperatures on Earth

  14. Heat of vaporization Evaporative cooling Organisms rely on heat of vaporization to remove body heat

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