Vital Water

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Water

Text of Vital Water

  • 1. Vital Water Alice NewtonUniversity of Algarve Joint Master in Water and Coastal Management University of Bergen 2005-2006

2. Bibliography

  • Books :
    • Philip Ball 1999:H 2 O A biography of Water ISBN 0 75381 092 1
    • Peter H. Gleick 1993:Water in CrisisOxford University Press
    • Open University course team 1997 : Seawater: its composition, properties and behaviour
    • Frank J. Millero 1996 : Chemical Oceanography, CRC Press

3. Bibliography 2

  • Web
    • United Nations Environment Program www.unep.org Vital Water Graphics
    • Global International Water Assessment www.giwa.net
    • Intergovernemntal Panel on Climate Change www.IPCC.org

4. Objectives

  • Vital water is an introductory lecture that relatesboth to integrated river basin management or integrated coastal zone management
  • It also links up with many other modules in the course

5. Requirements

  • No special skills are required for this lecture
  • A knowledge of basic inorganic and environmental chemistry is useful.

6. Programme

  • The constituents of water
  • The water molecule
  • Properties of water
  • The origin of water
  • The hydrological cycle
  • Composition of natural waters
  • Ice and glaciation
  • Water and life
  • Water the destroyer
  • Water and society, resources, uses and abuses

7. Learning outcomes

  • After completing this module you should know:that although water is a very common substance on Earth, it has strange properties and is a scarce resource
  • After completing this module you should be able to:Explain why water is so special and what some consequences are for water and coastal management

8. Other skills

  • Consult scientific literature and websites

9. The Constituents of Watera little chemistry

  • Hydrogen (H )
  • Oxygen (O)
  • H 2 O is the basic unit of water
  • Ratio 2:1 is a consequence of the atomic structure

10. Hydrogen(H)

  • About of the mass of the Universe is Hydrogen!
  • H atom has 1 proton
  • H usually has no neutrons, so the atomic mass is 1
  • 0.000015 % of H has 1 neutron, so atomic mass is 2 (1 proton + 1 neutron)
    • This isotope (different number of neutrons) is called heavy water, Deuterium, or Hydrogen-2

11. Oxygen(O)

  • O atom has 8 protons
  • Mass of O is about 16 x mass of H (different isotopes and neutons)
  • O can have 7,8 , 9 or 10 neutrons
  • O is the third most abundant element in the Universe
  • (the second most abundant element in the Universe is Helium, relatively unreactive)

12. The Origin of H and Oa little cosmo-chemistry

  • Current scientifictheory
  • Protons (H + ) formed a millionth of a second after Big Bang,T~ a trillion degrees
  • Nucleosynthesis started one hundredth of a second later (protons+neutrons),T~ three billion degrees
  • Hydrogen atoms form, T~ 4000 C

13. The Origin of H, O and Water

  • Gravity leads to formation of Galaxies and StarsHans Bethe 1939
  • Elements (C-N- O) formed in stars byfusion
  • Mainly generates15 O but also16 O17 OBurbridge,Burbridge, Fowler and Hoyle 1957
  • Water formed byreactionof H and O

14. From Element to compound

  • Water classically was thought of as an Element
  • Lavoisiers experiments 1784 prove that water is formed by burning Hydrogen in the presence of oxygen. Hydrogen means water former
  • Nicholson and Carlisle split water by electrolysis to form hydrogen and oxygen
  • Berzelius recognized the fixed ratios H=2, O=1

15. Wateras a Liquid 16. Liquid water

  • At present most of the water on Earth is in the liquid phase
  • Most liquid water (~97%) is in seawater
  • Water is the main component (~96%) of seawater

17. The Water Molecule

  • Hydrogen (H) and Oxygen (O)
  • H 2 O is the basic unit of water
  • Ratio 2:1
  • Consequence ofatomicand molecularstructure

18. Molecular Structure of Water

  • Hydrogen atoms havea partial positive charge.
  • Oxygen has 2 unbondedpairs of electrons withpartial negative charges.
  • Tetrahedral, distorted by charges to minimize repulsion
  • Molecular structure is "bent" to yield a104.5angle between the hydrogen atoms instead of 109.5 for a regular tetrahedron .

19. Hydrogen bonds

  • A partly positive hydrogen atom of one water molecule attracts the partly negative unbonded electron pair in the oxygen atom, forming a hydrogen bond.

20. Hydrogen bonds

  • The oxygen atom of a water molecule is the hydrogen bond acceptor for two hydrogen atoms .
  • Each O-H group serves as a hydrogen bond donor.

21. 4 Hydrogen bonds

  • Leads to the formationof4 hydrogen bonds by water
  • The tetrahedral structureof the water hydrogen bondsis a consequence of the sp3hybridization of theoxygen's electrons.
  • The two hydrogen bonds between the oxygen and the hydrogen atoms on another water molecule utilize the two partly-negative pairs of unbonded electrons on oxygen.

22. Structure of liquid water

  • The hydrogen bonding pattern of water is more irregular than that of ice.
  • The absolute structure of liquid waterhas not been determined .
  • Many theoriese.g.Frank and Wenflickering cluster model : as a liquid, water has partly crystalline clusters but some loose molecules

23. Properties of Water The Strange Liquid 24. Density anomaly

  • Most substances are denser in the solid than in the liquid phase
  • The structure of ice at 0 o C is less dense than that of liquid water at 0 o Cbecause ice has a more rigid lattice.
  • Density maximum at 4 o C
  • Ice forms at surface and floats
  • Enormous implications for climate

25. High SpecificHeat Capacity

  • Very high energy required tochange the temperatureof water
  • Water is slow to heat and slow to cool
  • Warm ocean currents can therefore transport huge amounts of heat
  • Gulf Stream transports more heat daily than would be produced by burning global quantity of coal mined annually

26. Latent Heat Capacity

  • Energy tochange phasewithout changing temperature
  • When water isheated to 100C, is doesnt all instantly evaporate to steam. A lot of heat has to be supplied to transform all the liquid into vapour.
  • When ice isreaches 0C, is doesnt all instantly melt. A lot more heat must be applied to transform all the ice into liquid water

27. Specific HeatandLatent Heat Heat Energy Supplied 100 C 0 C T C Boiling Point Freezing Point Specific Heat of Water Specific Heat of Ice Latent Heat ofWater LatentHeatof Ice 28. Phase transitions solid-liquid-gas

  • Boundaries ofphasesare controlled by temperature and pressure
  • Phase diagramplots phases on a graph of temperature and pressure

T P 29. Phase diagram of water 30. Triple Point

  • Solid, Liquid andGas phasescan co-exist
  • BelowTriple Point , solidsublimesto gas
  • Gas and Solid extend throughout T and P
  • Liquid is a contigent state, not always necessary

31. CriticalPoint

  • Boundarybetween Liquidand Solid stops atCritical Point
  • Supercritical region: gas and liquid behave in same way
  • Gas and Liquid are bothFluids phases

32. More anomalous properties

  • Excellentsolvent , especially of ionic compounds
  • Highlyreactiveand therefore corrosive
  • Viscosity increases with pressure
  • High boiling point and freezing point
  • Low dissociation, but can act as an Acid or Alkali and is an electrolyte

33. Water as Ice 34. Molecular structure of ice

  • Water molecules in ice form an open hexagonal lattice in which every water molecule is hydrogen bonded to four others.
  • The geometric regularity of these hydrogen bonds contributes to the strength of the ice crystal.
  • All hydrogen bonds are satisfied in ice.

Structure of Ice I normal ice 35. Normal ice

  • Ice I hashexagonal symmetrythat we associate with snowflakes
  • Dendritic( branching ) growth from a seed particle

36. Many types of ice

  • Under pressure, Ice I can change to other formse.g.ice II andice III.
  • 1998 Ice XII was discovered!
  • Some forms are very unsta