NEW AIM: What is so important about water?

1. Chapter 3 – Water and the fitness of the environment NEW AIM: What is so important about water?

2. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Lone pair electrons O H H Water has a bent geometry because the lone pair electrons in the valence shell of oxygen repel the electrons in ths O-H bonds giving it a “v” shape.

3. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Electronegativity: An elements attraction (affinity for) electrons. Remember that affinity for electrons depends on the charge of the nucleus AND the distance the electrons are from the nucleus. The further they are, the weaker the EM force. The fewer the protons in the nucleus, the weaker the EM force.

4. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Electronegativity: An elements attraction (affinity for) electrons. Therefore, as you move left to right on the periodic table, the electronegativity increases since the nucleus is getting larger, but the distance from the nucleus is staying the same.

5. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Electronegativity: An elements attraction (affinity for) electrons. As you move up a group, the electronegativity increases. This is because the valence shell electrons get closer to the nucleus (they have fewer shells/orbitals) even though the nuclei have fewer protons. Fluorine has the highest electronegativity. Why not neon or helium? Neon/Helium have a full valence shell and therefore are already stable all by themselves and will not attract electrons to be stable. In biology, we will focus on elements with high electronegativity like oxygen and nitrogen.

6. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? O H H

7. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Oxygen has a higher electronegativity than hydrogen and therefore the shared electrons will be more likely to be around oxygen than hydrogen giving oxygen a partial negative charge and hydrogen a partial positive charge.

8. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Polar vs Non-polar covalent bonds A polar covalent bond results when two elements of different electronegativity form a covalent bond resulting in an unequal sharing of electrons. One becomes partially negative and the other becomes partially positive. Ex. O-H : the O is partially neg. and the H is partially positive since oxygen has a higher electronegativity compare to hydrogen.

9. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Polar vs Non-polar covalent bonds They are called “polar” because they have opposite ends (one end is partial neg. and the other is partial pos.). The Earth has poles or is polar – north pole and south pole. Bipolar personality disorder – sometimes manic and sometimes depressed. Magnets are polar – north pole and south pole.

10. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Polar vs Non-polar covalent bonds A non-polar covalent bond results when two elements of similar electronegativity form a covalent bond resulting in an equal sharing of electrons. Both ends of the bond are neutral. Ex. C-C or C-H bonds.

11. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Why is the C-H covalent bond considered non-polar while the O-H and N-H bonds are polar? Carbon has 6 protons, while hydrogen has 1 proton. Therefore, in terms of nuclei, Carbon wins, but hydrogen only has one shell and carbon has two. Therefore, the electrons are much closer to hydrogen than to carbon. The closer distance balances the smaller number of protons in the nucleus resulting in carbon and hydrogen having a similar electronegativity.

12. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Which bonds are Polar and which are non-polar?

13. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Polar and Non-polar Molecules Most molecules are a mix of polar and non-polar covalent bonds. The ratio will determine how polar/non-polar the molecules will be.

14. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? How would multiple water molecules interact with each other?

15. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? The partially negative oxygens will be attracted to the partially positive hydrogens forming what is called a hydrogen bond.

16. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Hydrogen bonding A hydrogen bond (H-bond) is a weak bond (weaker than an ionic or covalent bond) formed between two partially charged atoms, one of which is a hydrogen. Each water can make up to four H-bonds, one to each hydrogen and one to each of the lone pairs. In liquid water, the H-bonds are constantly being formed and broken. http://www.visionlearning.com/library/module_viewer.php?mid=57

17. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? How would multiple water molecules interact with a non-polar molecule?

18. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Water molecules will not interact with non-polar molecules because non-polar molecules have no charge to “stick” to. Water molecules interact with other charged substances.

19. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? The molecule on the right is mostly non-polar (almost all C-C and C-H bonds). This region is known as the hydrophobic (water-fearing) end since it will not interact with water. The other end has some polar covalent bonds (C=O, O-H, C-O) making the tip of this molecule hydrophilic (water-loving) because water can H-bond to this part.

20. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Compare and contrast covalent, ionic and hydrogen bonds Covalent bonds share electrons between two atoms to satisify the valence shells (C-C). Ionic bonds result from donating elecrons from one atom to another resulting in a full and opposite charge in each atom, which causes them to attract each other (Na+ Cl-). Hydrogen bonds occur between partially charged atoms, one of which is typically a hydrogen. They result because of unequal sharing of electrons in covalent bonds due to differences in electronegativity. Bond Strengths: H-bonds are weaker than ionic and covalent bonds since only partial charges hold the two substances together.

21. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? What about Van der Waals Interactions (London dispersion)? Even non-polar molecules may have some positively and negatively charged region briefly and therefore can very weakly bind to each other… Dipole = two poles, or a positive side and a negative side. For example, a carbonyl (C=O) is a dipole as the carbon is partially positive and the oxygen partially negative. Figure 1. Two non-polar molecules (say H2) come into close proximity Figure 2. By chance, the position of the electrons around one of the molecules (the one of the left) are more on one side of the molecule than the other causing one side to be ever so slightly negative and the other side to be ever so slightly positive. Figure 3. This will then induce a dipole in the neighboring molecule as the neighboring molecule’s electrons will be attracted to the slightly positive region of the first molecule resulting again in an ever so slightly negative side and an ever so slightly positive side. Of course, the negative and positive will form a very weak interaction.

22. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Weak interactions add up… Think about velcro. Velcro consists of on side having numerous tiny hooks and the other having “fuzz” for each hook to wrap around. A single hook/fuzz interaction is extremely weak… However, hundreds of thousands of such interactions are additive and become important in the case of velcro jumping. Where do we see such additive affects of weak bonds in biological systems?

23. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Weak interactions add up… Where do we see such additive affects of weak bonds in biological systems? Plasma membrane are stabilized by the additive affect of Van der Waals interactions between non-polar fatty acid tails of phospholipids. The two strands of a DNA molecule are held together tightly by the additive affect of many, many weak Hydrogen Bonds

24. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Weak interactions add up… Where do we see such additive affects of weak bonds in biological systems? Geckos have been shown to walk up walls using countless numbers of Van der Waals interactions…

25. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? ? How is a water molecule held together A water molecule itself is held together by covalent bonds.

26. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? ? How are water molecules held together Water molecules are held to each other in liquid and solid (ice) by hydrogen bonds.

27. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? What determines the properties of water? Structure (Geometry/Shape and Polarity/charge) All of water’s properties are the product of its molecular structure/charge. All matter, including yourself, cannot be properly understood unless you understand the underlying molecular structures.

28. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Water is the only substance in nature to exist in the three common states of matter – liquid, solid, gas

29. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? This image demonstrates the cohesive (sticks to itself by H-bonds) properties of water. This is what holds it in droplet form. The leaf us covered with non-polar molecules, which is why the water will not stick to it (there is no charge to interact with)

30. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Cohesion gives water surface tension as the water molecules H-bond to each other on the surface forming a very delicate sheet that insects like this water strider can actually walk on without breaking.

31. Chapters 32: Plant Nutrition and Transport Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? How do plants get water/minerals from the roots to the leaves against the force of gravity without a mechanical pump like out heart? Transpiration - loss of water from leaves (stomata) pull xylem sap (water/minerals) upward - Two properties of water that make this possible: a. cohesion (water hydrogen-bonding to other waters): makes the xylem sap like a continuous string of “water beads” b. Adhesion (waterhydrogen-bonding to other molecules): sticks to cellulose walls of xylem cells Recall that the xylem is a network of dead cells involved in transporting water and minerals up from the soil. Fig. 32.3

32. Chapters 32: Plant Nutrition and Transport Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? How do plants get water/minerals from the roots to the leaves against the force of gravity without a mechanical pump like out heart? Transpiration - water molecule at end of chain in leaf is heated by solar energy - This molecule is “knocked” out of the stomateand evaporates - As it does this, it pulls on the neighboring waters that it hydrogen bonds to (cohesion), the neighbors pull on their neighbors and so on all the way to the roots (Without the suns KE, the water in the leaf would remain stuck to its neighbors - no pulling force, no transpiration) Fig. 32.3

33. Chapters 32: Plant Nutrition and Transport Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? How do plants get water/minerals from the roots to the leaves against the force of gravity without a mechanical pump like out heart? Transpiration - What about adhesion? - adhesion counters downward pull of gravity by “grabbing” (hydrogen bonding to) walls of xylem - holds water in xylem when transpiration is not occurring (at night) Fig. 32.3

34. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Heat Temperature vs Heat is referring to molecular motion. The “hotter” something is, the quicker the molecules are moving/vibrating. If something hot touches you like a hot iron, the rapidly vibrating molecules with crash into your skin causing your skin molecules to vibrate rapidly resulting in damage to the structure of your molecules/cells. It is the measure of the total amount of KE due to molecular motion in a body of matter. Temperature is the average motion of all the molecules in a substance. For example, in a glass of water that is 98.6 F (body temperature) the molecules have a certain average speed (about 700 meters per second). However, some will be moving faster than that and some will be moving slower. The temperature just tells us the average motion or KE of all the molecules.

35. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? What is specific heat? The amount of “energy” (collisions) it takes to heat up 1 gram of the substance by 1 degree Celcius. It takes a lot of energy to do this to water: 1 calorie (cal) of energy to be exact). Therefore the specific heat of water = 1 cal/g/°C Another way to say this is specific heat is a measure of how well as substance resists a change in temperature. 1 cal = 4.184 Joules (J)

36. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Water, because of it H-bonding (cohesive nature) has a very high specific heat relative to other molecules. This is because when molecules collide with the water molecules, it is difficult to get them vibrating since those waters are all sticking to each other. The H-bonds need to be broken. Think about the analogy in class where it is easy to push a single student and get them moving fast, but if you all hold hands, it becomes more difficult as I would need to break those bonds. Conclusion: water can absorb a great deal of energy without its temperature rising too greatly and vice versa, which is why it takes quite a bit of time to boil water on your stove relative to boiling another liquid like ethanol whose specific heat is 0.6 cal/g/°C.

37. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Because of the high specific heat, the temperature of coastal regions, especially islands, are regulated. During the summer, the water absorbs a lot of the sunlight’s energy and only heats up minimally resulting in cooler air temperatures. During winter, the water releases the energy warming the air keeping the winters warmer.

38. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Great Ocean Conveyor Belt delivering heat to the Northern Hemisphere….

39. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? The Great Ocean Conveyor Belt, as you should have learned in Earth Science, is a massive global current that carries energy from the sunlight at the equator, which is stored as heat in the water, up to the North keeping North America and Europe much warmer than it would be otherwise. One of the many fears of global warming is a disruption of this current resulting in colder temperatures in the North and the next Ice Age.

40. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Water helps modulate our body temperature as well. Just like water regulates the temperatures of land masses, it also helps organisms to resist temperature changes. Once again, the high specific heat of water means that is takes a great deal of energy to heat it up. Therefore, we can burn a lot of glucose and fat to move around, but our bodies will not quickly overheat as a result.

41. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Evaporative COOLING Heat of Vaporization Amount of energy (heat) required to turn a substance from a liquid to a gas. What can you predict about water’s heat of vaporization and why do you predict this? It is relatively high because once again, the waters are all H-bonded to each other, which must be broken in order to evaporate.

42. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Evaporative COOLING We also use water to cool ourselves down when we do eventually start to overheat to maintain a homeostatic level of 98.6 F. How does this work? When we overheat, we sweat. The sweat (water, salt and a bit of urea) sits on our skin. The molecules of your skin, which are moving too quickly (because you are overheating) will bump into the water, The result is your molecules moving slower and the water speeding up (energy transfer). Some of the water will move fast enough to jump off of your body (evaporate), carrying the kinetic energy away with it thereby cooling you down.

43. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? The solid phase of water (ice) floats

44. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Why does ice float and does this matter in terms of life on this planet? Ice floats because it is less dense than liquid water. What does that mean? It means that the water molecules take up more space/volume when water freezes compared to when it is a liquid (density is mass/volume). The mass is the same, but the volume is greater. Why is the volume greater?

45. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? The volume is greater because when water is cooled down (the molecules slow down) each water molecule will eventually move slow enough to make the maximum (4) hydrogen bonds with other waters forming a crystal of water (ice). The crystal has large spaces in it that liquid water doesn’t have making it less dense. In liquid water, the water molecules are moving quickly and H-bonds are being made and broken constantly and those large spaces found in ice are filled in making liquid water more dense.

46. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? Great, but who cares if ice floats? Arguably, life would not exist. If ice were more dense, as it forms in winter it would sink making the bottoms of lakes/oceans/etc… colder and eventually a build up of ice would occur. This ice is deep enough that even in the summer it would not melt as it would be insulated by the upper layer of water. The ice would build winter after winter until the oceans/lake would be completely frozen. The great ocean conveyor belt certainly would not exist and the Earth would be a snowball…

47. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? euphausid shrimp below arctic ice Great, but who cares if ice floats? Therefore, ice is a barrier or insulator against the cold air above and protects waterways from freezing over allowing life to persist.

48. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? The Universal Solvent (Solution, solvent, solute) Solvent – that which is dissolving the solute Solute – that which is being dissolved Solution – the result of a solute being dissolved in a solvent, a homogeneous mixture

49. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? The Universal Solvent (Solution, solvent, solute) Water is referred to as the universal solvent because it can dissolve a huge number of different substances; all of which are hydrophilic (contain many polar covalent bonds) and or charged. Ex. Water can dissolve salts, proteins, carbohydrates, DNA, RNA, vitamins, minerals, phosphate, nitrate, and the list goes on and on… All of these molecules are hydrophilic.

50. Chapter 3 – Water and the fitness of the environment Chapter 2 - The Chemical Basis of Life AIM: What is so important about water? AIM: What is so important about water? What does it mean to dissolve?