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Water and the Fitness of the Environment

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  1. Water and the Fitness of the Environment

  2. Introduction Water makes life possible. All organisms are made mostly of water and live in an environment dominated by water. 70-95% of all cells are water. ¾ of the Earth is water. Water is found in 3 forms on Earth: water, ice, water vapor.

  3. Polar Molecule Water is a polar molecule- it is both slightly positive on one end and slightly negative on the other end.

  4. Click to view animation. animation

  5. Hydrogen Bonding Positive charge of one water molecule attaches to negative charge of another water molecule. All properties of water are a result of hydrogen bonding.

  6. Important Properties of Water • Cohesion • Adhesion • Surface Tension • High Specific Heat • High Heat of Vaporization • Ice Floats • Universal Solvent

  7. Adhesion & Cohesion Cohesion- water molecules sticking to each other. Adhesion- water molecules sticking to other substances.

  8. Click to view animation. animation

  9. Surface Tension Due to cohesion, it is difficult to break the surface of water. Ex. Skipping a rock

  10. High Specific HeatHigh Heat of Vaporization • It is difficult to heat or cool water. This helps stabilizes temperatures around the Earth. • A lot of heat is absorbed to evaporate water. Evaporation of sweat significantly cools the body surface.

  11. Ice Floats Ice is less dense than water

  12. Water is the Universal Solvent Solute- substance that is dissolved. Solvent- substance doing the dissolving. Solution- homogenous mixture of 2 or more substances. Biological fluids are important solutions!

  13. Hydrophilic vs. Hydrophobic • Hydrophilic- polar or ionic substances that have an affinity for water. salts, sugars, ions, etc. • Hydrophobic- nonpolar or non-ionic substances that repel water. fats

  14. Dissociation of Water Water has a tendency to separate into two ions: H2O  H+ + OH-

  15. Acids and Bases When there is additional H+ ions in a solution, we call the solution acidic. When there is additional OH- ions in a solution, we call the solution basic.

  16. pH Scale 0-14 <7 Acidic =7 Neutral > 7 Basic

  17. Buffers Substances that minimize changes in the concentrations of H+ or OH- in a solution. Buffers are found in human blood in order to maintain blood pH very close to 7.4

  18. Acid Rain Due to pollution of sulfur oxides and nitrogen oxides (mainly from the burning of fossil fuels), rain in many parts of the world is acidic. Acid Rain pH can be as low as 2 This leads to incredible biological damage, especially in lakes, ponds, and soil.

  19. QUIZ 1. What type of bonds exist between water molecules? Hydrogen bonds 2. The ability of water to cling to itself is due to: Cohesion 3. It is usually cooler near the beach during the summer because of which property of water: High specific heat 4. Life can live underwater through the coldest winters because: ICE floats 5. The bonds that are broken when water molecules vaporize are: a) ionic bonds b) hydrogen bonds c) polar covalent bonds d) nonpolar covalent bonds B- hydrogen bonds

  20. QUIZ 6. In salt water, what is the solute? Salt 7. What type of molecule does water dissolve more readily, hydrophobic or hydrophilic? Hydrophilic 8. Substances that have excessive H+ ions are considered: Acidic 9. A substance with a pH of 10.4 is considered: Basic • Which of the following is considered hydrophobic a) sugar b) pasta c) table salt d) wax D- wax