This document provides an overview of key chemistry concepts related to water and its importance for life. It discusses water's unique properties including its ability to form hydrogen bonds, act as a solvent, have lower density as a solid allowing ice to float, store and release heat via its high specific heat and heat of vaporization, and ionize into H+ and OH- ions determining pH. These special properties of water, especially its prevalence as the solvent for life processes and its role in moderating temperatures on Earth, make it uniquely suited to supporting life.

1. 2009-2010The Chemistry of Life

2. Why are we studying chemistry?Chemistry is the foundation of Biology

3. The World of ElementsHCONPSNaMgKCa

4. Elements & their valence shellsElements in the same column have the same valence & similar chemical propertiesRemembersome food chainsare built on reducing O to H2O& some on reducing S to H2S

5. –––Chemical reactivityAtoms tend tocomplete a partially filled valence shell orempty a partially filled valence shellThis tendency drives chemical reactions…and creates bonds

6. ––H2 (hydrogen gas)Covalent bondBonds in BiologyHydrogen bondH2OWeak bondshydrogen bondsattraction between + and –hydrophobic & hydrophilic interactionsinteractions with H2Ovan derWaals forcesionicStrong bondscovalent bondssharing electronsH2O

7. Nonpolar covalent bondPair of electrons shared equally by 2 atoms

8. example: hydrocarbons = CxHx

9. methane (CH4 )Lots of energy stored…& releasedbalanced, stable,good building block

10. HOxygenHPolar covalent bondsPair of electrons shared unequally by 2 atoms

11. example: water = H2O

12. oxygen has stronger “attraction” for the electrons than hydrogen

13. oxygen has higher electronegativity

14. water isa polar molecule

15. + vs – poles

16. leads to many interesting properties of water…+––––+

17. Hydrogen bondingH bondsHHOPolar water creates molecular attractions

18. attraction between positive H in one H2O molecule to negative O in another H2O

19. also can occur wherever an -OH exists in a larger molecule

20. Weak bond

21. but common in biology2010-2011Chemistry of LifeProperties of Water

22. More about WaterWhy are we studying water?All life occurs in waterinside & outside the cellChemistry of waterH2O molecules form H-bonds with each other+H attracted to –Ocreates a sticky molecule

23. Elixir of LifeSpecial properties of water1. cohesion & adhesionsurface tension, capillary action2. good solventmany molecules dissolve in H2Ohydrophilic vs. hydrophobic3. lower density as a solidice floats!4. high specific heatwater stores heat5. high heat of vaporizationheats & cools slowlyIce!I could use more ice!

24. 1. Cohesion & AdhesionCohesion

25. H bonding between H2O molecules