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Water & pH

Water & pH. Ch. 3 Water & the Fitness of the Environment. Acids & Bases. ACID : substance that release H+ into solution BASE : substance that releases OH- into solution pH : Measurement of H+ ions in solution pH Scale: 1-14 Acids : 1-6 Neutral : 7 Bases : 8-14.

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Water & pH

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  1. Water & pH Ch. 3 Water & the Fitness of the Environment

  2. Acids&Bases • ACID: substance that release H+ into solution • BASE: substance that releases OH- into solution • pH: Measurement of H+ ions in solution • pH Scale: 1-14 • Acids: 1-6 • Neutral: 7 • Bases: 8-14

  3. How Does the pH Scale Work? The ratio of H+ to OH- is used to measure how much acid is in a substance. The measurement of H+ ions has been “translated” to pH (power of hydrogen) pH = -log [H+]

  4. How Does the pH Scale Work? • If [H+] [OH-] = 10-14 Then – log 10-7 = -(-7) = 7 (neutral pH) • If pH = 1= Maximum H+ (very acidic) 7= neutral (pure water) 14= least H+ (very basic)

  5. Why do we care? • Organisms are very sensitive to pH • Ex: Human blood maintains pH of 7.4 • If it changes to 7.3 or 7.5, we’re in danger of dying • Can our radish seeds germinate in extreme pH? We’ll find out, won’t we?  • How do living organisms protect themselves? • Hooray for BUFFERS!

  6. Buffers Rock! • Buffer = group of substances that release OR absorb H+. Examples: Blood with carbonic acid (builds up in blood while you breathe) H2CO3 - HCO3- + H+

  7. Buffers Rock! H2CO3 - HCO3- + H+ • When pH is too high, release H+ in blood • This makes blood pH more acidic

  8. OR…. • HCO3- + H+ H2CO3 • When pH is too low (too many H+ ), the reaction reverses to make carbonic acid. • This reduces the H+ in our blood • This raises the pH

  9. Acid Rain • Rain more acidic than pH 5.6 • Caused by burning fossil fuels • Sulfur oxides and nitrogen oxides • Lowers pH in soil and bodies of water • Let’s try a germination experiment….

  10. Germination Experiment • Seeds must have moisture to sprout and grow. • Q: Is pure water required, OR, will any liquid do? • Control: dry paper towels • Independent var.: type of liquid • Dependent var.: # of sprouts from seeds

  11. Germination Experiment • Types of liquids: • Pure water • Diluted rubbing alcohol • Diluted vinegar • Soapy water Set up your assigned petri dishes today, and we’ll check back in on our seeds in a few days…

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