Water properties


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Water properties

  1. 1. Textbook Chapter 3, p.41-49 Properties of Water
  2. 2. 6 Properties of Water 1. Cohesion & adhesion 2. Low density solid 3. High specific heat capacity 4. High heat of vaporization & fusion 5. Solubility: a versatile solvent 6. Ionization: determines pH
  3. 3. 1. Cohesion & Adhesion Cohesion: the clinging of a substance to itself hydrogen bonds between water molecules holding water together Adhesion: the clinging of one substance to another E.g. Meniscus: hydrogen bonds between water molecules and the glass of a test tube
  4. 4. 1. Relevance of Cohesion & Adhesion
  5. 5. 1. Cohesion: SurfaceTension A measure of how difficult it is to break the surface of a liquid Surface tension is one of the results of cohesion in water  Video: A National Geographic video showing how a lizard employs the water pro
  6. 6. Water is most dense at 4o C Ice is less dense than water Water is the only type of matter which becomes less dense when a solid 2. Low Density Solid
  7. 7. 2. Low Density Solid
  8. 8. 2. Relevance of Low Density Aquatic life When the temperature of the atmosphere falls below 0o C, the water at the surface gradually freezes to ice The water under the ice remains at 4o C
  9. 9. 3. High Specific Heat Capacity Amount of heat energy needed to increase the temperature of a substance by 1o C Water has a high specific heat capacity: Water is capable of absorbing a lot of heat without increasing in temperature Demonstration: water balloon
  10. 10. 3. High Specific Heat Capacity
  11. 11. 3. Relevance of High Specific Heat Capacity Help organisms maintain constant body temperature Large bodies of water have moderating effect on nearby land temperature
  12. 12. 4. High Heat ofVaporization and Fusion Heat of vaporization: amount of heat a liquid must absorb to be converted to a gas Heat of fusion: amount of heat a solid must absorb to be converted to a liquid Water has high heat of both vaporization and fusion Relevance: sweat
  13. 13. 5. Solubility Versatile solvent due to its polarity Forms a hydration shell
  14. 14. 5. Solubility
  15. 15. 5. Solubility:Versatile Solvent Many molecules are able to dissolve in water if it has ionic and polar regions on its surface Some biologically significant solutes include salts, sugars, proteins, vitamins Organic matter may be hydrophilic or hydrophobic.
  16. 16. H2O H+ + OH- Dissociation of water is reversible and rare H+ and OH- very reactive, can disrupt pH balance pH = -log[H+ ] Relevance: Organisms are very sensitive to pH changes 6. Ionization: Determines pH
  17. 17. 6. Ionization: Buffers Substances that minimize changes in the concentrations of H+ and OH- accepts H+ from solutions when in excess and donate H+ to solutions when depleted Example: Human blood pH maintained by carbonic acid To reduce pH of solution H2CO3 H+ + HCO3- To increase pH of solution
  18. 18. Review: Acid-Base Chemistry
  19. 19. Review: Acid-Base Chemistry Example: Carbonic acid H2CO3 + H2O H+ + HCO3-
  20. 20. Review: Bronsted-Lowry Acid compounds that will donate a proton in solution results in a negative charge Base compounds that will receive a proton in solution results in a positive charge
  21. 21. HW Question Explain how 2 properties of water help maintain body temperature. [4 marks] Hint:You first need to figure out which 2 properties of water is relevant to this question.