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The Chemistry of Life

The Chemistry of Life

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The Chemistry of Life

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  1. The Chemistry of Life Properties of Water

  2. The Water Molecule • Neutral Charge • All Molecules Are Neutral

  3. The Water Molecule • Polarity • A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. (+) (—)

  4. Hydrogen Bonds • Polar water molecules act like magnets and attract each other • Hydrogen Bonds • The attraction of the Hydrogen end (+) of one molecule for the Oxygen end (-) of another water molecule. • They are the strongest bonds that can form betweenmolecules

  5. Hydrogen Bonds

  6. Cohesion • The attraction between molecules of the same substance (e.g. water). • Allows some insects and spiders to walk on water.

  7. Adhesion • Attraction between molecules of different substances • Responsible for Capillary forces in plants

  8. Solutions & Suspensions • Water is usually part of a mixture. • There are two types of mixtures: • Solutions • Suspensions

  9. Solution • Ionic compounds disperse as ions in water • Evenly distributed • SOLUTE • Substance that is being dissolved • SOLVENT • Substance into which the solute dissolves

  10. Solution

  11. Suspensions • Substances that don’t dissolve but separate into tiny pieces. • Water keeps the pieces suspended so they don’t settle out.

  12. Acids, Bases & pH • 1 water molecule in 550 million naturally dissociates into a Hydrogen Ion and a Hydroxide Ion Hydrogen Ion Hydroxide Ion Acid Base H2O  H+ + OH-

  13. The pH Scale • Indicates the concentration of H+ ions • Ranges from 0 – 14 • pH of 7 is neutral • pH 0 – 6.99 is acid … H+ • pH 7.01 – 14 is basic… OH- • Each pH unit represents a factor of 10 change in concentration

  14. Acids • Strong Acid = pH 1-3 H+ ions

  15. Bases • Strong Base = pH 11 – 14 OH-ions

  16. Buffers • Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH. Weak Acid Weak Base