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pH , Acids and Bases

pH , Acids and Bases. Pg 164-165. pH. Reminder: Water is held together by ___________________ bonds. These are relatively __________ bonds. These bonds are constantly _________ and _____________. Water molecules can naturally break apart. This is called the dissociation of water .

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pH , Acids and Bases

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  1. pH , Acids and Bases Pg 164-165

  2. pH • Reminder: Water is held together by ___________________ bonds. • These are relatively __________ bonds. • These bonds are constantly _________ and _____________. • Water molecules can naturally break apart. This is called the dissociation of water.

  3. Acids, Bases and pH One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-) Hydrogen Ion Hydroxide Ion Acid Base H2O  H+ + OH-

  4. The pH Scale **Some compounds form acids or bases Scientists use something called the pH scale to measure how acidic or basic a liquid is The scale looks at the concentration of positively charged hydrogen ions (H+) in a solution vs. the amount of negatively charged hydroxide ions (OH-) The scale goes from values 0 through 14. Brain pop

  5. Acids • An acid releases hydrogen ions when it dissolves in water. • HighH+concentration • Low OH- concentration • - pH less than 7 • Tastes sour • Corrodes metals

  6. Bases • Tastes bitter, chalky • Feels soapy, slippery A base releases hydroxide ions

  7. A B Left to right

  8. Summary! • If you have an ionic compound and you put it in water, it will break apart into two ions. • If one of those ions is H+, the solution is acidic. • If one of the ions is OH-, the solution is basic. There are other ions that make acidic and basic solutions, but we won't be talking about them here.

  9. ACIDBASE

  10. Neutral • Pure water contains small, but equal amounts of ions: H+ and OH- • On the pH scale the number is 7

  11. Acids vs Bases • Acids: Anything that dissolves in water and adds H+. • Bases: Anything that dissolves in water and adds OH- ions.

  12. Buffers • Buffer - mixtures that can react with acids or bases to prevent major pH changes. • Buffered aspirin has a coating on it to prevent the acids in your stomach from dissolving it right away.

  13. 9 8 7 6 Buffering range 5 pH 4 3 2 1 0 0 1 2 3 4 5 Amount of base added Buffers & Cellular Regulation • pH of cells must be kept ~7 • pH affects the shapeof molecules • shape of molecules affects function • pH affects cellular function • Buffers Control pH • donate H+ when [H+] falls • absorb H+ when [H+] rises Honors Biology

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