Seawater Chemistry 003

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

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

Protons (p + ) Neutrons (n o ) Electrons (e - )

proton neutron electron hydrogen atom helium atom carbon atom 1p, 0n, 1e-2p, 2n, 2e- 6p, 6n, 6e-

atomic number: number of p; #p = #e- 2 He  2e- and 2p He

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

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

O16O17O18 stable isotopes Isotope atoms that differ in the number of neutrons 16 8 O 18 8 O 17 8 O #p #p+n O

Major Elements Comprising the Biological Molecules of Living Things C arbonC arbon H ydrogenH ydrogen O xygenO xygen N itrogenN itrogen P hosphorusP hosphorus S ulfurS ulfur

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

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

Molecule Two or more atoms held together by chemical bonds OxygenO 2 NitrogenN 2 AmmoniaNH 3 Carbon DioxideCO 2 WaterH 2 O MethaneCH 4 GlucoseC 6 H 12 O 6

Carbohydrates: C 6 H 12 O 6 (glucose) Lipids: C 3 H 8 O 3 (glycerol) + 3C 16 H 32 O 2 (fatty acids) Proteins: COOH-NH 2 Nucleic Acids: sugar, PO 4, N 2 containing base Organic Molecules

Compound Binding two or more different kinds of elements together NaCl CH 4 C 6 H 12 O 6

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

Sodium (Na) Atom 11 P + 12 N o

Sodium (Na + ) Ion 11 P + 12 N o

Chlorine (Cl) Atom 17 P + 18 N o

Chloride (Cl - ) Ion 17 P + 18 N o

HydrogenH + PotassiumK + FluorideF - CalciumCa +2 MagnesiumMg +2 HydroxideOH -HydroxideOH - BicarbonateHCO 3 -BicarbonateHCO 3 - NitrateNO 3 -NitrateNO 3 - PhosphatePO 4 -3PhosphatePO 4 -3

Ionic Covalent Hydrogen

Transfer of electron 17 P + 18 N o 11 P + 12 N o

electron sharing O H H

Between Water Molecules Covalent bond Hydrogen bond

Boiling Point: 100 o C Freezing Point: 0 o C Density: 1g/cm 3 Properties of Water gasliquid solid

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%

IceDensity vs Temp ( o C)

Properties of Water 1.High heat capacity 2.High heat of vaporization 3.High Surface tension 4.Polarity solvent properties

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

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

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

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

Water has a high surface tension

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

Properties of Seawater Heat capacity: Heat capacity with salinity Evaporation: Evaporates more slowly than fw Specific gravity: Pure water density = g/cm 3 Seawater (2 o C) density = g/cm 3 Seawater’s Boiling Point: As salinity, the boiling point

When NaCl dissolves, each ion becomes hydrated

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

Salt IonIons in sw ( 0 / 00 ) Cl Na SO Mg Ca K HCO Br H 3 BO Sr F Total34.38

Na + - Weathering of crustal rock Cl - - from the mantle by way of volcanic vents and outgassing from mid-ocean rifts Mg ++ - mid ocean rifts

White sections represent warm surface currents. Purple sections represent deep cold currents

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

Bases Na + + OH -  NaOH NH 3 + H +  NH 4 OH - + H +  H 2 O HCO 3 +H +  H 2 CO 3 Proton acceptor, i.e., they take up H+ ions NaOH is a strong base ~pH 12

Neutralization HCl + NaOH  H 2 O + NaCl

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

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

Bases Na + + OH -  NaOH NH 3 + H +  NH 4 OH - + H +  H 2 O HCO 3 - +H +  H 2 CO 3 Proton acceptor, i.e., they take up H+ ions NaOH is a strong base ~pH 12

Neutralization- HCl + NaOH  H 2 O + NaCl Buffer- resists dramatic changes in pH; ex. tums, rolaids…buffers stomach acid Neutralization & Buffers

pH Scale Acidic0-6 Neutral7 Basic (alkaline)8-14 Type of Solution pH Value 0-14

pH Scale Logarithmic scale

Depth (m) Concentration of dissolved gas (ppm) O 2 CO CO 2 O2O2 O 2 and CO 2 vs ocean depth Compensation depth

Carbon Dioxide System in the Ocean Respiration Photosynthesis C 6 H 12 O 6 +6O 2 6CO 2 + 6H 2 O 6CO 2 + 6H 2 O C 6 H 12 O 6 +6O 2 Air Water CO 2 gas

CO 2 + H 2 O ↔ H 2 CO 3 ↔ HCO H + ↔ CO H + By-product of respiration carbonic acid bicarbonate carbonate The addition of CO 2 makes water acidic The effects of pH in an ocean system

Carbonate buffer Seawater too basic: H 2 CO 3 HCO H + pH drops Seawater too acidic: HCO H + H 2 CO 3 pH rises

Ocean Acidity

Global Ocean Acidity.

Consequences of Ocean Acidity Animals with CaCO 3 skeletons affected Plankton Corals Mollusks Fish Fisheries

In a high CO 2 world, the ocean will be… More acidic More stratified More oligotrophic, but better light conditions Less oxygenated Consequences of Ocean Acidity

Inquiry 1.How many neutrons in 7 N? 2.Why do all the oceans have relatively the same proportion of salinity? 3.At what temperature is fw most dense? 4.Of the following pH’s which is most acidic? Why are there no plants at the compensation depth? 6. Why can a water strider walk on water? 7. Besides temperature and salinity, what physical factor effects thermohaline circulation? 8. What is the oceans most dense sea water called? 14