Exploring Seawater Chemistry: Elements, Molecules, and Properties

1. 003 Seawater Chemistry

2. Elements Pure substances that cannot be broken down into simpler chemical entities by ordinary chemical reactions. Periodic Table 112 known elements

4. Elements & Atoms An element is composed of atoms (0.1-1 nm in diameter) Atom cluster of small particles (proton, neutron, electron)

5. Subatomic Particles Protons (p +) Neutrons (n o) Electrons (e -)

6. Electron Configuration of Atoms proton neutron electron hydrogen atom helium atom carbon atom 1p, 0n, 1e- 2p, 2n, 2e- 6p, 6n, 6e-

7. atomic number: number ofp; #p = #e- 2He2e- and 2p He

8. He atomic mass (atomic wt.): sum of masses ofp+n He 2p + 2n, atomic mass = 4 4 2He p + n e-

9. C Carbon Atom p = n = e- = Atomic number = Atomic mass =

10. O Isotope atoms that differ in the number of neutrons 16 8 O 17 8 O 18 8 O #p+n #p O16 O17 O18 stable isotopes

11. Major Elements Comprising the Biological Molecules of Living Things • Carbon • Hydrogen • Oxygen • Nitrogen • Phosphorus • Sulfur

12. Other Major Elements of Living Things • Calcium (Ca) • Potassium (K) • Chlorine (Cl) • Magnesium (Mg)

13. Some Important Trace Elements of Living Things • Boron (B) • Cobalt (Co) • Iron (Fe) • Copper (Cu) • Fluorine (F) • Zinc (Zn)

14. Molecule Two or more atoms held together by chemical bonds Oxygen O2 Nitrogen N2 Ammonia NH3 Carbon Dioxide CO2 Water H2O Methane CH4 Glucose C6H12O6

15. Organic Molecules • Carbohydrates: C6H12O6 (glucose) • Lipids: C3H8O3 (glycerol) + 3C16H32O2 (fatty acids) • Proteins: COOH-NH2 • Nucleic Acids: sugar, PO4, N2 containing base

16. Compound Binding two or more different kinds of elements together NaCl CH4 C6H12O6

17. Ion An atom that has either gained or lost electrons such that it exhibits a net charge Na+ Cl-

18. Sodium (Na) Atom 11 P+ 12 No

19. 11 P+ 12 No Sodium (Na+) Ion

20. 17 P+ 18 No Chlorine (Cl) Atom

21. 17 P+ 18 No Chloride (Cl-) Ion

22. Examples of Ions • Hydrogen H+ • Potassium K+ • Fluoride F- • Calcium Ca+2 • Magnesium Mg+2 • Hydroxide OH- • Bicarbonate HCO3- • Nitrate NO3- • Phosphate PO4-3

23. Bond Types • Ionic • Covalent • Hydrogen

24. 11 P+ 12 No Ionic Bonds Transfer of electron 17 P+ 18 No

25. O electron sharing Covalent Bonds H H

26. Between Water Molecules Hydrogen Bonds Hydrogen bond Covalent bond

27. Properties of Water Boiling Point: 100oC Freezing Point: 0oC Density: 1g/cm3 solid gas liquid

28. The formation of ice • As water cools to 4°C: • Molecules slow • Water contracts • Density increases • Below 4°C: • Hydrogen bonds form • Water expands • As water freezes: • Expands by 9%

29. Ice Density vs Temp (oC)

30. Properties of Water • High heat capacity • High heat of vaporization • High Surface tension • Polarity solvent properties

31. The ocean moderates coastal temperatures • Water has high heat capacity, so it can absorb (or release) large quantities of heat without changing temperature • Moderates coastal temperatures

32. Hawaii Average High and Low Temperature The ocean moderates coastal temperatures Hawaii Average Ocean Water Temperature

33. Interconnections of water molecules • Polarity causes water molecules to form weak (hydrogen) bonds between water molecules • Water sticks to itself and to other substances • Allows water to be the universal solvent

34. Water as a solvent • Water dissolves table salt (NaCl) by attracting oppositely charged particles • Pulls particles out of NaCl structure to dissolve it

35. Water has a high surface tension

36. Water in the 3 states of matter • Latent (hidden) heat = energy that is either absorbed or released as water changes state

37. Properties of Seawater • Heat capacity: • Heat capacity with salinity • Evaporation: • Evaporates more slowly than fw • Specific gravity: • Pure water density = 1.000 g/cm3 • Seawater (2 oC) density = 1.028 g/cm3 • Seawater’s Boiling Point: • As salinity , the boiling point

38. NaCl NaCl in water When NaCl dissolves, each ion becomes hydrated

39. Seawater’s Freezing Point: • As salinity , the freezing point • Salt is an antifreeze- doesn’t freeze until -2oC (@35 o/oo) Sea ice (pancake ice) Lattice structure of an ice crystal

40. Major Solutes in Seawater Salt Ion Ions in sw (0/00) Cl- 18.980 Na+ 10.556 SO42- 2.649 Mg2+ 1.272 Ca2+ 0.400 K+ 0.380 HCO3- 0.140 Br- 0.065 H3BO3 0.026 Sr2+ 0.013 F- 0.001 Total 34.38

41. Source of Ocean Salts: • Na+ - Weathering of crustal rock • Cl- - from the mantle by way of volcanic vents and outgassing from mid-ocean rifts • Mg ++ - mid ocean rifts

42. Thermohaline Circulation White sections represent warm surface currents. Purple sections represent deep cold currents

43. Thermohaline Circulation

44. Thermohaline Circulation

45. Acids Proton donor, i.e., they donate H+ ions HCl is a strong acid with a pH 1-2 HCL  H+ + Cl-

46. Bases Proton acceptor, i.e., they take up H+ ions NaOH is a strong base ~pH 12 Na+ + OH- NaOH NH3 + H+ NH4 OH -+ H+ H2O HCO3 +H+ H2CO3

47. Neutralization HCl + NaOH H2O + NaCl

48. Buffer- resists dramatic changes in pH; ex. tums, rolaids…buffers stomach acid

49. Acids Proton donor, i.e., they donate H+ ions HCl is a strong acid with a pH 1-2 HCL  H+ + Cl-

50. Bases Proton acceptor, i.e., they take up H+ ions NaOH is a strong base ~pH 12 Na+ + OH- NaOH NH3 + H+ NH4 OH -+ H+ H2O HCO3- +H+ H2CO3