Water and the Fitness of the Environment

1. Water and the Fitness of the Environment

2. What molecule supports all of life?

3. Transport over land Solar energy Net movement of water vapor by wind Precipitation over land Precipitation over ocean Evaporation from ocean Evapotranspiration from land Water Cycle Percolation through soil Runoff and groundwater

4. How does the polarity of water affect its properties? • What is a polar molecule? • Has polar bonds • Water has polar covalent bonds • Oxygen is more electronegative than H • Electrons of covalent bonds spend more time closer to Oxygen than to H • Creates a polar molecule • O region is partially negative • H regions are partially positive • Causes the anomalous properties of water

5. – O POLAR MOLECULE H H + + H2O

6. – + Water (H2O) + Hydrogen bond – HYDROGEN BONDS Ammonia (NH3) + + +

7. States of Water

8. How does this change when water is in different states? • Slightly positive H of 1 molecule is attracted to slightly negative O of nearby molecule creating a H bond that holds those molecules together • Hydrogen bonds by themselves are not that strong; however, when they are continuously forming, re-forming, breaking, then at any instant a large percentage of water molecules are hydrogen-bonded to neighbors

9. Hydrogen bonds Water and Polarity

10. What are the 4 Emergent Properties of Water? • Cohesive behavior • Ability to moderate temperature • Expansion up freezing • Versatility as a solvent

11. What are the 4 Emergent Properties of Water?Cohesive Behavior • What is cohesion? • Molecules are linked by multiple hydrogen bonds which make water more structured than other liquids • Collectively, hydrogen bonds hold substance together = Cohesion

12. Water-conducting cells Water and Cohesion 100 µm

13. What are the 4 Emergent Properties of Water?Cohesive Behavior • Contributes to transport of water and dissolved nutrients against gravity in plants • There exists a network of water-conducting cells help water reach the leaves from the roots What starts the process?

14. Adhesion

15. What are the 4 Emergent Properties of Water?Cohesive Behavior • Cohesion is supported by Adhesion • What is Adhesion? • clinging of one substance to another • Adhesion of water to cell walls by those same hydrogen bonds

16. What are the 4 Emergent Properties of Water?Cohesive Behavior • How is this related to Surface Tension? • Surface tension= how difficult it is to stretch or break the surface of a liquid

17. What are the 4 Emergent Properties of Water?Cohesive Behavior • Benefits: • Bugs that walk on water • Bugs that use air bubble to breath underwater • Leads to transport of water and its dissolved nutrients against gravity in plants • Water molecules leaving tree through evaporation cause its H bonds to tug on water molecules in the tree creating an upward force of water

18. Hydrogen bonds Water and Temperature

19. What are the 4 Emergent Properties of Water?Ability to Moderate Temperature • How does water moderate air temperature? • By absorbing heat from the air that is warmer and releasing stored heat to air that is cooler • Can absorb or release a large amount of heat with only slight change in its own temperature

20. What are the 4 Emergent Properties of Water?Ability to Moderate Temperature • How does this work? 1st - Have to understand what heat is: • Heat is a form of energy • Measure of the amount of heat is a measure of the matter’s TOTAL kinetic energy due to motion of its molecules and depends on matter’s volume • The energy of motion= kinetic energy • Related to temperature, but not same • Temperature= measure of heat intensity that represents the average kinetic energy of the molecules, regardless of volume

21. What are the 4 Emergent Properties of Water?Ability to Moderate Temperature • How does this work? • Water stabilizes temperatures from its relatively high specific heat • Specific Heat- • is defined as the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 °C • For Water- 1 calorie per gram per °C = 1 cal/g/°C • Because has high specific heat relative to other material, water will change its temperature less when it absorbs or loses a given amount of heat

22. What are the 4 Emergent Properties of Water?Ability to Moderate Temperature • How does this work? • In order to absorb heat, bonds must be broken • Because once one bond is broken, it can reform with another molecule, the heat absorbed is lost through the reforming of bonds, • Much of the actual heat absorbed is used to break the bonds before the molecules can begin moving faster • Water has a high specific heat and high heat of vaporization

23. What are the 4 Emergent Properties of Water?Ability to Moderate Temperature • What is Evaporative cooling? • Molecules moving fast enough to overcome the attraction to each other, can leave the liquid and enter the air as gas • Called Vaporization orEvaporation • Heat of vaporization • Quantity of heat a liquid must absorb for 1 g of it to be converted from liquid to the gaseous state • High specific heat= high heat of vaporization • Caused by the H bond

24. Evaporative Cooling

25. Evaporative Cooling in plants

26. What are the 4 Emergent Properties of Water?Ability to Moderate Temperature • What is Evaporative cooling? • As liquid evaporates, the surface of the liquid that remains behind cools down • Occurs because the “hottest” molecules with greatest kinetic energy, are the most likely to leave as a gas

27. What are the 4 Emergent Properties of Water?Ability to Moderate Temperature • Benefits: • Bodies of water maintain a constant temperature keeping its inhabitants from going into heat shock on a hot day • Keeps water warm on a cool day and cool on a hot day, and in turn, cools the air around it on a hot day and heats air around it on a cool day • Keeps temp for fluctuating greatly due to the fact that oceans cover the earth • Helps moderate Earth’s climate bc amount of solar heat absorbed by tropical seas is consumed during the evaporation of surface water • Contributes to stability of temperature in lakes and ponds and provides mechanism that prevents terrestrial organisms for overheating

28. What happens to the ice?

29. What are the 4 Emergent Properties of Water?Expansion Upon Freezing • Water is less dense as a solid than as a liquid • Ice Floats • Begins freezing when its molecules are no longer moving vigorously enough to break their hydrogen bonds • Above 4 degrees C acts like any other liquid, but below, freezes at 0 degrees locking the water molecules in place in their very structured arrangement • Becomes about 10% less dense • Creates H bonds at arms’ length from each other • When absorbs enough heat for water to rise above 0°C then the H bonds become disrupted

30. Hydrogen Bond angles

31. What are the 4 Emergent Properties of Water?Expansion Upon Freezing • What happens after 0°C? • Water reaches its greatest density at 4°C and begins to expand as the molecules move faster

32. What are the 4 Emergent Properties of Water?Expansion Upon Freezing • Benefits: • Fish get to survive in cold temperatures • We get cold drinks

33. Universal Solvent

34. What are the 4 Emergent Properties of Water?Versatility as a Solvent • Solution- • Liquid that is completely homogeneous mixture of two or more substances • Solvent- • Dissolving agent of a solution • Solute- • Substance that is dissolved • Aqueous solution- • Solution in which water is the solvent

35. Solution

36. Suspension

37. ColloidThis is why you should shake milk first

38. What are the 4 Emergent Properties of Water?Versatility as a Solvent • Why is water such a versatile solvent? • Due to polarity of the ions • Ions have mutual affinity through electrical attraction of the opposite charges • For this reason, water molecules surround the individual ions, separating and shielding them from one another, creating a hydration shell • Hydration shell- sphere of water molecules around each dissolved ion • Compounds don’t have to be ionic to dissolve water • Dissolve when water molecules surround each of the solute molecules, forming hydrogen bonds with them

39. What are the 4 Emergent Properties of Water?Versatility as a Solvent • It’s ability to be such a great solvent, led to the creation of the two terms: • Hydrophilic • Any substance that has an affinity for water • Can be hydrophilic without dissolving- • Substances that are suspended in the aqueous solution create mixtures called: colloid • Stable suspension of fine particles in a liquid • Hydrophobic • Any substance that does not have an affinity for water • Generally substances that are nonionic and nonpolar • Seems to repel water

40. What are the 4 Emergent Properties of Water?Versatility as a Solvent • Benefits: • Allows the movement of solvents through cohesion • Makes the solvent hydrophilic, benefitting cellular processes

41. How can you determine how many atoms and molecules are involved and present in an aqueous solution? • Use mass to calculate the number of molecules • Process: • Know: • Mass of each atom in molecule • Calculate: • Molecular Mass • Sum of masses of all the atoms in a molecule

42. How can you determine how many atoms and molecules are involved and present in an aqueous solution? • Example: • C6H12O6 = Glucose • (12 daltons) x 6 + (1 daltons) x 12 + (16 daltons) x 6 = 72+12+96 = 180 daltons • Glucose has a molecular mass of 180 daltons • Not practical to measure out 1 molecule of something, instead we use mole

43. How can you determine how many atoms and molecules are involved and present in an aqueous solution? • Know: • Mole = (mol) = represents an exact number of objects – 6.02 x 1023 • 6.02 x 1023 = Avogadro’s number • There are 6.02 x 1023daltons in 1 gram • Calculate : • Molar mass • Use the molecular mass to determine the grams of the molecule to give 6.02 x 1023 molecules of the substance = 1 mol of the substance

44. How can you determine how many atoms and molecules are involved and present in an aqueous solution? • Example: • Glucose has a molecular mass of 180 daltons • Therefore, there are 180 grams for 1 mol of glucose • What is the point of this? • If you want to make a 1:1 mixture of something, using mol makes it easier to create that mixture because you can’t just mix 10 grams of one and 10 grams of the other because it might not represent a 1:1 molecular mixture because the molecules have different weights

45. How can you determine how many atoms and molecules are involved and present in an aqueous solution? • What if you wanted to make a solution? • Determine the molar mass and add enough water to bring the total volume of the solution up to 1 L = 1 Molar solution • Molarity= the number of moles of solute per liter of solution

46. What are Acids and Bases? • Hydrogen ion- • H+ • Occurs when a hydrogen atom participating in a hydrogen bond between two water molecules shifts from one molecule to the other • Hydrogen atom leaves it electron behind • what is actually transferred is a hydrogen atom with a positive charge • a single proton with a charge of +1

47. What are Acids and Bases? • hydroxide ion – • OH- • The water molecule that lost the proton • Has a charge of 1-

48. What are Acids and Bases? • Hydronium ion – • H30+ • Occurs when the proton binds to another water molecule • This reaction is reversible

50. What are Acids and Bases? • Overall, what effect does this have? • H+ does not exist solitarily, always associated with another water molecule • The reversible reaction is generally at a dynamic equilibrium when water molecules dissociate at the same rate that they are being re-formed from H+ and OH- • These concentrations are equal in pure water • By themselves, H+ and OH- are very reactive • Adding solutes (Acids and Bases) disrupt the balance present in pure water