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