Ap bio ch 2 ppt The Chemistry of Life and Water

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  • 1. Ch 2 The Chemical Basis of Life Element- substance that can’t be broken down into simpler substances.• # of protons makes each unique
  • 2. Atom – smallest unit of matter• Composed of:• 1. Protons, +, in nucleus• 2. Neutrons, o, in nucleus• 3. Electrons, -, orbit nucleus in shells or levels http://www.youtube.c om/watch?v=sWVX_ rGzzQU&feature=rel ated Atom animation
  • 3. GoldMercury
  • 4. Define & distinguish among atomic number, mass number, atomic weight, and valence• Valence is the number of electrons needed to fill the outermost shell of an atom.
  • 5. Interactions between atoms:• Atoms strive to fill their outer shell w/ e-. To do this they’ll share e- or steal e-• 1st level max of 2• 2nd level – 8
  • 6. Is this sodium atom satisfied? What could it do?
  • 7. Compare these twoWhat do you notice is different? How doyou think that would affect its charge? +
  • 8. Is Chlorine satisfied?What could it do? How do you think that would affect it? -
  • 9. If I couldonly get rid Heyof this one Sodium,electron in my outer I’ll takeshell I’d be it! I satisfied! need one more to be satisfied!Hey, baby …I + Hey, babysuddenly … I feel the feel this same way.attraction It’s like we have this to you. bond…
  • 10. Ionic bond – attraction between opp. charged ions• + charged ion – ion with less electrons than protons• - charged ion – ion with more electrons than protons
  • 11. Covalent bond - atoms share electrons to bond… http://www.wellesley.edu/Biology/Concepts/Html/c ovalentbonding.html
  • 12. Polar Covalent bond - atoms share electrons unequally to bond…
  • 13. Molecule- 2 or more atoms that share e-• Represented by formulas• Ex: H2
  • 14. Water is SUPER!
  • 15. Unique properties of H2O Bonds b/t the O and H atoms in H2O - polar covalent bond.• Polar covalent bond – unequal sharing of electrons.• Occurs b/c O “hogs” the electrons
  • 16. Water is polarPolar – one side is +and other side is –Due to O hoggingelectrons.
  • 17. 1. Orgs depend on the cohesion of water molecules.• Cohesion – when H bonds hold a substance together. Contributes to transport of water against gravity in plants. Adhesion – the clinging of one substance to another Ex: Miniscus Surface tension – a measure of how difficult it is to stretch or break surface of a liquid. Due to H bonds Skin
  • 18. H –bonds make water molecules stick to each other• Weak bonds between water molecules due to its polarity.
  • 19. Jesus Lizzard• http://www.visionlearning.com/library/mod ule_viewer.php?mid=57&l=&c3=• Link above!
  • 20. 2. Water contributes to Earth’s habitability by moderating temperatures.• It absorbs heat from warmer air & releases heat into cooler air.• Ice cools drinks by absorbing heat• Heat – measure of the total quantity of kinetic E.• Temperature – measure of the intensity of heat due to the average kinetic E of the molecules.Swimmer in ocean has a higher temp than water but the ocean contain far more heat due to its volume.
  • 21. • Specific heat – amt of heat that must be absorbed or lost for 1 g of that substance to change its temp by 1 C.• measure of how well a substance resists changing its temp.• Water - high specific heat. 1cal/g/C• To increase temp of H2O heat must be absorbed to break H bonds.• To decrease temp of H2O heat must be released to form H bonds. When enough H bonds are formed, it’s solid – ice.• This is why it actually gets a little warmer when the rain turns to snow… heat is released when the H bonds form.
  • 22. Why is water important to life?3. Cools orgs when they sweat, pant, or roll in mud b/c the hottest molecules are leaving the surface - evaporative cooling.
  • 23. Why is water important to life?4. Oceans and lakes don’t freeze solid b/c ice is less dense than water so it floats. Less dense b/c when H-bonds form, water molecules are farther apart.
  • 24. Diffusion• Diffusion = random movement of molecules high concentration to less• Ex: smell of popcorn spreads The Diffusion Applet
  • 25. Diffusion• Continues until all molecules are evenly spread out.• Dynamic equilibrium = concentration of molecules are even but molecules are still moving.• It’s how molecules get into & out of our cells
  • 26. Diffusion• The faster the molecules are moving, the faster diffusion will occur.
  • 27. Why is water important to life?5. Many substances dissolve in it because it is polar.
  • 28. Terms to know…SoluteSolventHydrophilicHydrophobic
  • 29. Solute concentration in aqueous solutionsMole – equal in # to the molecular wt. but upscaled to gramsMolecular wt – sum of wts of all atoms in a moleculeSo… to obtain 1 mol of sucrose (C12H22O11):C = 12 (daltons) x 12 (atoms present) = 144H = 1 x 22 = 22O = 16 x 11 = 176Molecular wt = 342 g
  • 30. molarity• # of moles of solute per liter of solutionSo… to make a 1 molar solution of sucrose you would add 1 liter of water to 342g of sucroseA 0.2 molar solution of sucrose?Add 1 liter of water to 68.4g of sucrose (342 x 0.2)
  • 31. Orgs are sensitive to changes in pHAcid – substance that increases the H+ of a solutionBase – substance that reduces the H+ of a solution & has more OH- ions.
  • 32. pH scale• In any solution the product of the H+ and OH- is 10-14• from 0-14 used to show H+ concentrations• Each pH unit represents a tenfold diff in the concentration of H+• pH declines as H+ increases