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Water : A Molecule Essential for Life

Water : A Molecule Essential for Life. Thoughts to Ponder……. Why can’t we survive more than a week without water? How does water rise up 300 feet from the roots of a redwood tree without a pump? Why does water take so long to boil? Can it really boil faster if salt is added?

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Water : A Molecule Essential for Life

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  1. Water : A Molecule Essential for Life

  2. Thoughts to Ponder…… • Why can’t we survive more than a week without water? • How does water rise up 300 feet from the roots of a redwood tree without a pump? • Why does water take so long to boil? • Can it really boil faster if salt is added? • Why do oil and water not mix?

  3. And how does this Spider Walk on Water? Source: http://static.flickr.com/82/237875014_4d579d57c5.jpg

  4. Life is dependent on Water Why? Source: http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-earth.html

  5. Water has unique properties that support life due to its structure http://www.lenntech.com/images/Water%20molecule.jpg

  6. Water is a Covalently bonded molecule– Hydrogen and Oxygen share electrons

  7. The electrons are not shared equally– the Oxygen atom pulls the shared electrons closer to itself.This “pulling force” is called electronegativity. Negative Pole Positive Pole http://rst.gsfc.nasa.gov/Sect20/water_molecules_con_c_la_784.jpg

  8. Electrons that are shared by hydrogen and oxygen stay closer to the Oxygen atom because oxygen has a greater electronegativity than hydrogen.

  9. Because the e- are closer to the oxygen atom, it gets a slight/partial negative charge

  10. Because the e- are away from the hydrogen atom, it gets a slight/partial positive charge

  11. A molecule that has different charges on opposite sidesis called a Polar Molecule Water is one example of a Polar Molecule. Negative Pole/ Side Positive Pole/Side http://rst.gsfc.nasa.gov/Sect20/water_molecules_con_c_la_784.jpg

  12. What else do you know of that has opposite poles or sides?

  13. A polar molecule behaves a like a magnet due to having different charges on either side

  14. Water’s polarity gives it the ability to form hydrogen bonds with other charged molecules or ions.A hydrogen bond is an attractive force between a positivelycharged hydrogen atom in one molecule and an negatively charged atomor ionin a differentmolecule.

  15. One hydrogen bond is notvery strong - it doesn’t require much energy to break it. But when there are many hydrogen bonds working together A LOTof energyis needed to break the bonds.

  16. Strength in Numbers! Let’s be water molecules and try this out! Source: www.personal.psu.edu/.../ bonddiagram.gif.

  17. This is why it takes so much energy to melt and evaporate water – billions of hydrogen bonds must first be broken before the individual molecules can be separated.

  18. Hydrogen Bond Formation Intermolecular force Between molecules Intramolecular force Within molecule http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page3.html

  19. Intramolecular bonds – form between atoms within the same moleculeEx. Covalent and Ionic bonds • Intermolecular bonds – form between atoms in different molecules Ex. Hydrogen bonds

  20. Oxygen’s electronegativity -> Water’s polar structure -> Hydrogen bondingThese characteristics of water molecules give rise to the properties that support life.It is an important example of how a molecule’s structuredetermines how it functions /what it can do. Remember a common theme is biology:Structure and Functionare related.

  21. Water’s ability to Hydrogen Bond gives it Properties which Support Life • Cohesion / Surface Tension • Adhesion • High heat capacity • Dissolves polar and ionic compounds • Hydrophobic effect on nonpolar substances • Expands and less dense as it freezes

  22. Cohesion Because water is a polar molecule it is attracted to itself Cohesion – the attractive force between Water molecules Water molecules“stick” together Creates surface tension

  23. Adhesion Water molecules are attracted to other charged molecules. (Polar molecules/Ions)_

  24. Capillarity Capillarity – ability of water to move upwards in small tubes due to its attraction for each other (cohesion) AND the solid surface it’s in contact with (adhesion).

  25. Ex.’s of Capillarity

  26. Water exists in all three states (liquid, solid, gas) over a wide range of temperatures • 32 – 212 F • 0 – 100 C

  27. High Heat capacity Water can absorb and release large quantities of heat energy without changing its temperature. Ex. It takes a long time for water to boil and to cool down. http://i.telegraph.co.uk/multimedia/archive/01549/perspiration_1549996c.jpg

  28. When’s the water the warmest at the beach?

  29. High Heat Holding Capacity Cities located near large bodies of water benefit from this property The slow release of heat the water absorbed in the summer warms their air in the winterand the absorption of heat energy cools their air in the summer. Water helps to maintain stable temperatures Our bodies are made of 70% water which helps keep our temp. stable

  30. High Vaporization Energy Large amounts of heat E are needed to break the hydrogen bonds between liquid water molecules so they can evaporate into gas. Sweating is a homeostatic mechanism designed to cool your body down as heat from your body is used to evaporate the sweat

  31. Universal Solvent The “Great Dissolver” Water’s ability to hydrogen bond lets it dissolve many polar and ioniccompounds which also have a charge.

  32. 2 Parts of a Solution • Solvent 1. Substance that’s present in the greater amount 2. Dissolves another substance • Solute 1. Substance that’s present in lesser amount 2. Gets dissolved

  33. Water “the Great Dissolver” • “Like Dissolves Like” • Water dissolves many ions and molecules that can be carried throughout the body in blood and urine (both of which are mostly water) • Most chemical reactions must occur in water STAY HYDRATED – YOUR HEALTH DEPENDS ON IT!

  34. Hydrophobic effect on Nonpolarsubstances Water cannot dissolve nonpolar substances like fats, waxes and oils – they have No Chargeto attract water with. “Oil and Water Don’t Mix” As Water molecules hydrogen bondwith each other they exclude nonpolar substances - Hydrophobic effect Causes molecules like DNA and proteinsto fold into their specific shapes

  35. Why Water and Oil Don’t Mix • Water is NOT able to dissolve nonpolar molecules (molecules that don’t have a charge) • Examples of nonpolar molecules: *Fats *Waxes *Oils

  36. When fat molecules and water molecules are mixed, water molecules are attracted to each other by hydrogen bond and push the fat molecules away because they can’t hydrogen bond with them • YouTube: Why Oil and Water Don't Mix

  37. Density Anamoly The space between water molecules expands as water freezes making ice less dense than liquid water - ice floats Water bodies freeze from the top down with the ice insulating the water and organisms below.

  38. Biology Crash Course Videos • Water - Liquid Awesome https://www.youtube.com/watch?v=HVT3Y3_gHGg • Polar and Nonpolar molecules https://www.youtube.com/watch?v=PVL24HAesnc

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