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KEY CONCEPT Water’s unique properties allow life to exist on Earth.

KEY CONCEPT Water’s unique properties allow life to exist on Earth. Objectives for Section 2-2. Elaborate on how life depends on the hydrogen bonds in water Discuss how many compounds dissolve in water State how acids and bases are formed. _. O. H. H. +. +.

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KEY CONCEPT Water’s unique properties allow life to exist on Earth.

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  1. KEY CONCEPTWater’s unique properties allow life to exist on Earth.

  2. Objectives for Section 2-2 • Elaborate on how life depends on the hydrogen bonds in water • Discuss how many compounds dissolve in water • State how acids and bases are formed

  3. _ O H H + + Life depends on hydrogen bonds in water. • Water is a polar molecule. • Polar molecules have slightly charged regions. -Polarity means having two opposite poles (positive + and negative -)

  4. -Nonpolar molecules do not have charged regions • Hydrogen bonds form between slightly positive hydrogen atoms and slightly negative atoms.

  5. Chemistry in Biology What do you notice here? 

  6. Hydrogen bonds are responsible for three important properties of water. • (1) high specific heat  resists changes in temperature

  7. -(2) Cohesion- attraction among molecules (water to water) • Water beads • Surface tension

  8. -(3)Adhesion – attraction between different substances • Paper towel • Water transport in plants

  9. Many compounds dissolve in water. • A solution is formed when one substance dissolves in another. • Homogeneous(same) mixture. • Solvents dissolve other substances. • Solutes dissolve in a solvent.

  10. Water is a great (Universal) solvent -Many important life-sustaining substances dissolve in water in your blood (blood is mostly water) -Oxygen, nutrients, enzymes, and hormones carried to cells by blood & move easily through cell membranes because they are dissolved in water

  11. Polar solvents dissolve polar solutes. (water) • Nonpolar solvents dissolve nonpolar solutes. (oil) • “Like dissolves like.” -Polar substances and nonpolar substances generally remain separate. (i.e. oil and water)

  12. stomach acid pH between 1 and 3 more acidic Some compounds form acids or bases. • An acid releases a hydrogen ion (H+) when it dissolves in water. • high H+ concentration • pH less than 7

  13. bile pH between 8 and 9 more basic • A base removes hydrogen ions from a solution. • low H+ concentration; high hydroxide (OH-) conc. • pH greater than 7

  14. pure water pH 7 • A neutral solution (pure water) has a pH of 7.

  15. pH can be regulated by buffers • Mixtures that can react with acids or bases to keep pH within a particular range • Blood (pH 7.5) is your buffer • Homeostasis!

  16. Quick Quiz Time  • Each question will be worth 2 points • You may NOT talk and/or communicate with a classmate • Scores will be collected and recorded at the end of the chapter

  17. 4. The attraction among molecules of different substances is called • Cohesion • Adhesion • Specific heat • Surface tension

  18. 5. Why is water necessary to your body? • It prevents large changes in blood pH • It dissolves and transports substances • It dissolves nonpolar fats and oils • It forms the solutes in blood plasma

  19. 6. Hydrogen Bonds can form between regions of polar molecules that are • Nonpolar • Negatively charged • Oppositely charged • Uncharged (neutral)

  20. End of Show

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