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Properties of Water

Properties of Water. Chapter 2. Water (H 2 O). Most important inorganic molecule in living things. Living organisms = 75-80% H 2 O. Many biological processes require H 2 O Survive 21-24 days without food Survive 3 days without water. Three Physical States of H 2 O. Solid (ice) Liquid

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Properties of Water

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  1. Properties of Water Chapter 2

  2. Water (H2O) • Most important inorganic molecule in living things. • Living organisms = 75-80% H2O. • Many biological processes require H2O • Survive 21-24 days without food • Survive 3 days without water

  3. Three Physical States of H2O • Solid (ice) • Liquid • Gas (vapor)

  4. Properties of Water • Buoyancy • Polarity • Cohesion • Adhesion • Surface Tension • High Specific Heat • Forms solutions • Neutral pH

  5. Heats Slowly & Cools Slowly • High Specific Heat- a lot of heat is needed to raise the temperature of 1 gram of H2O by 1°C • H2O retains heat & cools slowly. • Ex: pool/ocean is warm in the fall. • Allows organisms to maintain relatively constant body temperatures.

  6. Polar Molecule • Atoms of different elements don’t always share e- equally. • More protons (+) in the nucleus means a stronger attraction for electrons (-).

  7. Polar Molecule • e- drawn the nucleus with more protons MORE than the others. • Charges form  polar molecules or polar regions of large molecules

  8. Cohesion- ability of H2O molecules to resist coming apart. • Keeps H2O molecules together as they move from roots to leaves. Giant Sequoia

  9. Cohesion and Surface Tension • How droplets of H2O form. • Attraction between H2O molecules  surface tension • Surface Tension- molecules in the surface layer are H-bonded to H2O molecules below them. • Prevents water’s surface from easily breaking. Water Strider Droplet Formation

  10. Adhesion • Adhesion- attraction between H2O molecules and molecules of other substances (that can form H-Bonds). • Due to polarity of H2O • Other polar substances get wet (mix with H2O) • Nonpolar molecules, like oils, do not.

  11. Adhesion and Capillary Action • Attraction of H2O to surfaces with a charge  capillary action • Capillary Action- tendency of liquids to rise in tubes of small diameter. • Explains movement of H2O from roots  leaves

  12. Forms Solutions • Many substances dissolve in H2O. • Solution- mixture in which 1+ substances are evenly distributed in another substance. • Can be mixtures of liquids, solids, or gases. • Substances transported in organisms as solutions of water. • Ex: Plasma (liquid part of blood)- made up of various ions and macromolecules, as well as gases, that are dissolved in H2O.

  13. Parts of Solutions • Solute- substance being dissolved. • Ex: Sugar • Solvent- substance in which solute is dissolved. • Ex: H2O Sugar + H2O  Sugar H2O **Sugar & H2O molecules remain unchanged and can be separated again.**

  14. Low Density Solid • Ice (solid) is LESS dense than liquid H2O.

  15. Acids and Bases • Bonds break between some water molecules as they collide. • Forms a H ion (H+) and a hydroxide ion (OH-). • Pure H2O ALWAYS has a low concentration of H+ and OH- ions • H+ ions = OH- ions

  16. Acids and Bases • Compounds that form H+ when dissolved in H2O are acids. • Adding acids to pure H2O  H+ level increases above that of pure H2O • Bases- compounds that reduce [H+] in a solution. • Many bases form OH- when dissolved in H2O. • Lower [H+] because OH- reacts with H+ to form H2O.

  17. Acids and Bases • pH scale- measures H+ concentration in a solution.

  18. Acids and Bases • Each whole # (on pH scale) represents a factor of 10. • Solution with pH 5 has 10 times more H+ than a solution with pH 6. • Note: Stomach acid pH= 2 Blood pH= 7.5

  19. Questions • Lemons have a pH of 2. Are lemons acidic or basic? • The strongest bases have a pH of ____. • Pure water is a neutral substance. What is the pH of pure water?

  20. Animations/Tutorials/Videos • Matter: http://www.teachersdomain.org/asset/lsps07_int_naturematter/ • Matter Video Review: http://www.teachersdomain.org/asset/psu06-nano_vid_matter/ • Atomic Structure: http://www.teachersdomain.org/asset/lsps07_int_theatom/ • Chemical Bonding: http://www.teachersdomain.org/asset/lsps07_int_chembonds/ • Water Video: http://www.teachersdomain.org/asset/idptv11_vid_d4ksow/ • NOVA Hunting the Elements Video: http://www.pbs.org/wgbh/nova/physics/hunting-elements.html

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