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Water Walk

Water Walk. 10 Different pictures/scenarios with brief description Write Down Number of Station and the scenario you are looking at. Start at the number of the station you are at Move clockwise Answer the following questions for each…

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Water Walk

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  1. Water Walk • 10 Different pictures/scenarios with brief description • Write Down Number of Station and the scenario you are looking at. • Start at the number of the station you are at • Move clockwise • Answer the following questions for each… • How does the structure of water relate to this action/scenario?

  2. Water The Solvent of Life

  3. Water • Chemical Formula • H2O • How water isformed • Covalent compound • Whichatom has a stronger pull for electrons? • The one thatisbigger…oxygen • Electrons are shared but theyspend more time aroundOxygenatomthan the hydrogenatoms • This makes water a… • Polar Molecule • Uneven sharing of electrons • slight positive charge by hydrogens • Slightnegative charge by oxygen • POLARITY • What do opposites do? • Water molecules are attracted to other water molecules to formHYDROGEN BONDS • Weak attraction betweenhydrogenatom of one molecule and an oxygen, nitrogen or sulfur bond of anothermolecule.

  4. LE 3-2

  5. Van der Waals Force • slightly polar side of one molecule being attracted another molecule with the slightly opposite charge • NOT a covalent bond….just a little attraction • Hydrogen bonds are a type of Van der Waals force

  6. *****HYDROGEN BOND***** • Weak attraction between hydrogen atom of one molecule (it will be the slightly positive side) and an oxygen, nitrogen or sulfur bond of another molecule (which will be the slightly negative side).

  7. Mixture, Solutions and Suspensions…oh my!

  8. A little bit about water • Water is the biological medium on Earth • Universal Solvent • Solvent: the substance that the solute (salt) is dissovled in (water) • Solute: substance (salt) that is dissolved in a liquid • Solution: when solutes are uniformly distributed throughout a water solvent • Water is a versatile solvent due to its polarity • Most cells are surrounded by water, and cells themselves are about 70-95% water • The abundance of water is the main reason the Earth is habitable

  9. Mixtures • physically, not chemically mixed compounds • Not necessarily evenly distributed • Homogenous mixtures • Evenly distributed • Cannot see the different parts • SOLUTIONS are homogenous mix. • Heterogenous mixtures • Not uniformly distributed • you can see the parts • SUSPENSIONS are heterogenous mix.

  10. Special types of mixtures… • Solution • Homogenous Mixture • components are uniformly distributed • Solutes and solvents • Ex. Salt water • Suspension • Mixture of water and non-dissolved material • Some of the most biologically important substances are both solutions and suspensions • Ex. blood

  11. Water as the Universal Solvent • Water is an effective solvent because it readily forms hydrogen bonds • When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules, a hydration shell • Water can also dissolve compounds made of nonionic polar molecules • Even large polar molecules such as proteins can dissolve in water if they have ionic and polar regions

  12. – Na+ + – + – + – – LE 3-6 Na+ – + + Cl– Cl– + – – + – + – –

  13. LE 3-7a Lysozyme molecule in a nonaqueous environment.

  14. LE 3-7b Lysozyme molecule in a aqueous environment.

  15. Properties of water • Versatility as a solvent • Polarity and hydrogen bonds • Cohesive and Adhesivebehavior • Capillaryactiondefygravity • Expansion uponfreezing • Solid water floats • High specificheat (heatcapacity) • EnablesTemperaturemoderation

  16. Versatility as a solvent (review) • Why can certain substances dissolve readily in water whole others cannot? (Answer in your notes!)

  17. How are water molecules moving in liquid water? • Constant, slow, un-directional movement • “wandering aimlessly” • Think ZOMBIES!

  18. What happens when we throw something POLAR or CHARGED into the Water? • Water molecules ATTACK! • They surround the polar/charged substance • Think Zombies hearing/seeing their next meal…they ALL attack and surround it!

  19. Zombie Water Molecules!!! • Always trying to get around the polar/charged molecules….

  20. Cohesive and Adhesivebehavior • Cohesion: whensimilarmolecules stick together (droplet of water) • hydrogen bonds hold water molecules together • Cohesion helps the transport of water against gravity in plants • Adhesion:whenunlikemolecules stick together (water on glass) • Adhesion of water to plant cell walls also helps to counter gravity • Start thinking… • How does water getfromroots to the leaves of a talltree?

  21. Cohesion accounts for SURFACE TENSION • Surface tension is a measure of how hard it is to break the surface of a liquid

  22. Capillary Action • DEF: The movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension • Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules.

  23. Capillary Action • Think of what happens when you dip a paper towel in water • What happens when you put celery in colored water • How does water getfromroots to the leaves of a talltree?

  24. How does water move through a plant??? • Roots to leaves…. • What do they travel through? • Plants have vessels like us • We have arteries and veins….plants have xylem and phloem • XYLEM • Carries water from roots to leaves so photosynthesis can occur and some times water leaves as water vapor through little pores on the underside of leaves • PHLOEM • Carries glucose made from photosynthesis to all other plant cells that need energy

  25. Transpiration: • Evaporation of water through the leaves of plants • “stomata”are the tiny pores in the leaves of plants through which water (and oxygen) escapes…carbon dioxide enters here…

  26. Expansion Upon Freezing • Liquid H2O WATER! • Molecules of a liquid move how? • Slide past each other! • Hydrogen bonds between water molecules keep breaking and reforming • Solid H2OICE! • Hydrogen bonds become stuck on whatever nearby water molecule they are attached to • Now molecules cannot slide past each other…therefore, they CANNOT pack densely together • Liquid water is more dense, therefore… • ICE FLOATS!!!

  27. Heat and Temperature • Kinetic energy is the energy of motion • Heat is a measure of the total amount of kinetic energy due to molecular motion • Temperature measures the intensity of heat due to the average kinetic energy of molecules

  28. How Does Energy (Heat) Move? • From where there is HIGH ENERGY (hot area/object) to where there is less energy (cooler area/object)…keeps transferring until they are STABLE  (do you see a pattern here in science…?)

  29. Water’s High Specific Heat • The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 gram of that substance to change its temperature by 1ºC • Water’s high specific heat minimizes temperature fluctuations to within limits that permit life • Heat is absorbed when hydrogen bonds break • Heat is released when hydrogen bonds form

  30. What Happens When Hydrogen Bonds Form Between Water Molecules? • ENERGY is Released!!! • Energy=HEAT • So…when water freezes, is energy released or absorbed? • RELEASED! • When water freezes, its warms up its surroundings.

  31. What Happens When Hydrogen Bonds Between Water Molecules Break??? • This REQUIRES ENERGY!!! • Energy or HEAT MUST Be absorbed • To break hydrogen bonds, you just need to add heat…

  32. High Specific Heat allows…Moderation of Temperature • Water absorbs heat from warmer air and releases stored heat to cooler air • Water can absorb or release a large amount of heat with only a slight change in its own temperature

  33. Weather and Water • Coastal Areas • During the hot day, the ocean/lake will absorb energy from the air so that it feels cooler • At night, when the air is cooler, the water releases all the stored energy, making it warmer at night • “moderate” temperature • Inland areas (no water nearby) • During the hot day, there is NO water to absorb heat so it is realllllyy hot (think desert) • At night, no energy is release, so it gets very cold

  34. Evaporative Cooling • Evaporation is transformation of a substance from liquid to gas • Heat of vaporization is the heat a liquid must absorb for 1 gram to be converted to gas • As a liquid evaporates, its remaining surface cools, a process called evaporative cooling • Evaporative cooling of water helps stabilize temperatures in organisms and bodies of water (HOMEOSTASIS) • “Sweating” liquid to gas requires heat…this heat comes from inside our body • What does the saying “It’s not the heat, it’s the humidity”mean? • Humidity: water vapor in the air • If there is more water in the air, it is harder for water molecules to evaporate off and pull away the heat from your body…so how do you feel? • Hot and sticky!

  35. Hydrophilic and Hydrophobic Substances • A hydrophilic substance is one that has an affinity (likes!) for water • A hydrophobic substance is one that does not have an affinity (does NOT like; scared of) for water

  36. Surfactants • A “surface acting” agent • a compound which lowers the surface tension of a liquid, increasing the contact between the liquid and another substance • Surfactants have a hydrophobic tail attracted to NON-POLAR molecules and a Hydrophilic tail, which is POLAR and attracted to polar molecules (such as…WATER!) • There are a wide variety of surfactants, which work with oil, water, and an assortment of other liquids

  37. Types of Attractions(Strongest to Weakest) • Covalent • Ionic • Van der Waals Forces • Intermolecular force of attraction • Due to uneven sharing of electrons in covalent bonds • Slight attraction between oppositely charged regions of molecules that are closely packed together • Holds large molecules together

  38. Acids and Bases • What do you know?

  39. How water acts in solution • Occasionally a water molecule dissociates (breaks up) into ions H2O H+ + OH- This happens to every one water molecule in a million in pure water…not very common • The H+ immediately reacts with another water molecule in the solution to make a HYDRONIUM ion H30+

  40. The pH Scale • The pH of a solution is determined by the relative concentration of hydrogen ions H+ • So it is really measuring how acidic something is • formula is.. • pH=-log[H+] • Negative means opposite, this is why a low pH has MORE H+ ions • [x] means concentration • Acidic solutions have pH values less than 7 • More H+ ions • Basic solutions have pH values greater than 7 • More OH- ions, less H+ ions • Most biological fluids have pH values in the range of 6 to 8

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