WATER, A UNIQUE MOLECULE
H-O-H, H2O - 2 HYDROGEN ATOMS COVALENTLY BONDED TO 1 OXYGEN ATOM
ANGLE BETWEEN THE HYDROGEN ATOMS IN H-O-H IS 105°
- EXCELLENT SOLVENT FOR SOLIDS AND GASES
- HYDROGEN BONDS AFFECT ITS HEAT CAPACITY (HIGH), BOILING POINT & LATENT HEAT OF EVAPORATION (HIGH) 540 cal/g at 100o C, 585.6 cal/g at 20o C and 590.8 cal/g at 10o C, FREEZING POINT & LATENT HEAT OF FUSION (HIGH) Because of the high heat capacity of water it will heat slowly and it will cool down slowly.
Click here for phase changes for water.
- WATER IS NOT A GOOD CONDUCTOR OF HEAT - Water will heat at the surface but the heat will not be transfered downward. This leads to the formation of a thermocline.
Click here for phase changes for water.
- CAUSES COHESION LEADING TO SURFACE TENSION, AND ADHESION
- WATER HAS ITS GREATEST DENSITY (1 gm/cc) AT 3.98° C
- ICE IS LESS DENSE THAN WATER (INCREASED ANGLE TO 109° (which is the angle of a tetrahedron) RESULTING IN A 9% INCREASE IN VOLUME)
1. Ice will float allowing life in freshwater lakes to survive in the winter, since the ice insulates against further heat loss, causing the lake water to freeze at the surface, not at the bottom.
2. Below 3.98° C the density of water decreases as it approaches the freezing point. As a result this promotes the rapid expansion of water. The weathering of rocks occurs when water, trapped in crevices, expands with freezing.
3. The freezing point of water will decrease under pressure causing melting at the base of glaciers, which allows them to flow.
4. When hydrogen bonds are under pressure ice becomes plastic resulting in the flow of the inland ice of Antarctica and Greenland. This results in the calving of icebergs at glaciers' margins which then returns water to the sea from whence it first came through the process of evaporation. If this did not happen, all water would eventually be trapped in the glaciers and we would have no water in the ocean.
- TRANSPARENT - APPEARS BLUE/GREENThe open ocean appears bluish green while coastal waters such as those at Jones Beach appear brownish green. Why?
- fresh water's pH is neutral, (7.0).
UNIQUE PROPERTIES OF WATER:
- Cl- , Na+, S04-2, Mg+2, Ca+2, K+, HCO3-, TRACE ELEMENTS
- SALINITY (GRAMS OF SALT IN 1 KG OF WATER) AVERAGE 350/00
- SOURCES OF SALTS - CRUST AND EXCESS VOLATILES
- CONSERVATIVE CONSTITUENTS - occur in constant proportions or change very slowly, are the inert gases in the ocean and have long residency times. These are the most abundant dissolved materials in the ocean, i.e., chloride ion, sodium ion, nitrogen gas.
- NON-CONSERVATIVE CONSTITUENTS - substances that are used by organisms, tied seasonal cycles or are "used up". Biologically active gases such as CO2 and O2which are a part of photosynthesis and cellular respiration, silica and calcium needed for animal and plant shells, nitrates and phosphates needed as nutrients for phytoplankton, trace elements such as iron needed for biological activity, and elements with short residency times, usually less than 1,000 years (the mixing time for the ocean) such as aluminum (600 years) which is adsorbed unto the clays in ocean sediments.
- The salinity of the ocean at the equator is lower because there is greater precipitation than evaporation. The salinities are higher in the North and South Trade Wind Belts because there is more evaporation, due to the winds, than precipitation.
Methods of measuring salinity:
- SALINITY IN 0/00 = 1.80655 X CHLORINITY IN 0/00
- REFRACTOMETER, SALINOMETER (Water samples are collected in NANSEN BOTTLES)
- STEADY STATE OCEAN, RESIDENCE TIMES (varies from Chlorine ion 100,000,000 years to iron, only 200 years), MIXING TIME (1,000 YRS)
- THE AVERAGE pH OF SEA WATER IS 8 - alkaline.
- COLLIGATIVE PROPERTIES
Temperature and heat are not the same. Heat is a function of how many molecules are vibrating and how fast they are vibrating. Heat is measured in calories.
Temperature is only a measure of how fast the molecules are vibrating. Temperature is measured in degrees.
TEMPERATURE AFFECTS THE DENSITY - typically temperature and salinity contribute to the density of seawater. Higher salinity means greater density, colder water means higher density. It is possible to have seawater with different temperatures and salinities have the same density. In deep water, an increase in pressure will increase density.
LOWERS FREEZING POINT - lower than 0º celsius.
LOWERS HEAT CAPACITY
EVAPORATION IS SLOWER - salt ions attract the water molecules.
OSMOTIC PRESSURE CHANGES - depending on salinity.Click here for the Effects of Salinity, Temperature and Pressure on the Properties of Water.
LIGHT IN WATER
- SOLAR RADIATION (INSOLATION) = 7 MILLION calories/m2/day
- LIGHT ENTERING WATER IN REFRACTED (BENT)
- DIFFERENT WAVELENGTHS OF LIGHT ARE ABSORBED IN DIFFERENT AMOUNTS AT VARYING DEPTHS (RED AND IR IN UPPER METER), BLUE & GREEN PENETRATE MOST DEEPLY
The density of sea water depends on BOTH temperature and salinity. The ocean is organized into layers or "zones" dependent on the salinity and temperature of the water. There are areas in the ocean where the temperature changes sharply called the thermocline, where the salinity changes sharply called the halocline and where the density changes sharply called the pycnocline.
The three zones of the ocean are the surface zone or mixed layer, the pycnocline zone and the deep zone. The deep zone has relatively uniform temperature, salinity and density and it occupies 80% of the ocean.
SOUND IN WATER
- SOUND TRAVELS 331.6 m/sec or 1088 ft/sec at 0o C or 32o F.
- THE VELOCITY OF SOUND IN AIR TRAVELS FASTER AT HIGHER TEMPERATURES SO SOUND TRAVELS AT 344 m/sec or 1129 ft/sec at 20o C or 68o F.
- SOUND TRAVELS FASTER IN LESS DENSE AIR THAN DENSER AIR SO SOUND TRAVELS FASTER IN MOIST AIR WHICH IS LESS DENSE THAN DRY AIR SINCE IT CONTAINS LIGHTER WATER MOLECULES
- THE VELOCITY OF SOUND IN GASES IS DEPENDENT ON THE SPECIFIC HEAT OF THE GAS
- THE VELOCITY OF SOUND IS FASTER IN SOLIDS AND LIQUIDS.
- THE SPEED OF SOUND IN SOLIDS IS DIRECTLY DEPENDENT ON THE SQUARE ROOT OF THE ELASTICITY OF THE SOLID. SINCE STEEL IS MORE ELASTIC THAN COPPER IT IS A BETTER CONDUCTOR OF SOUND. NOTE AN INCREASE IN TEMPERATURE DECREASES THE SPEED OF SOUND IN A SOLID SINCE ITS ELASTICITY IS NORMALLY DECREASED.
- SOUND TRAVELS 5 TIMES FASTER IN WATER THAN IN AIR
- SPEED OF SOUND IN 350/00 WATER IS 1,500 m/sec or 3,345 mph
- SPEED OF SOUND INCREASES WITH AN INCREASE IN TEMPERATURE, PRESSURE AND SALINITY WITH A MINIMUM SPEED AT ABOUT 1,000 METERS SINCE THE TEMPERATURE DOES NOT SIGNIFICANTLY CHANGE BELOW THIS LEVEL BUT PRESSURE DOES
- SOUND IS USED BY VARIOUS MARINE MAMMALS TO COMMUNICATE AND TO FIND PREY BY ECHOLATION. HOWEVER THE USE OF SONAR BY THE NAVY CAN DAMAGE THE EARS OF THESE MAMMAL. SONAR LEVELS, 215 DECIBELS, ARE HIGHER THAN THE LEVEL, 180 DECIBELS, THAT WILL RUPTURE THE EAR DRUMS OF WHALES. MANY BEACHED WHALES AND DOLPHINS SHOW HEMORRHAGING AROUND THE BRAIN AND EAR BONES PROBABLY CAUSED BY SONAR.
- CARBON DIOXIDE (15% OF OCEAN GASES IS CO2, WHILE ONLY .035% IS CO2 ON LAND)
- OXYGEN (36% COMPARED TO 20.95% ON LAND)
- NITROGEN (48% COMPARED TO 78.08% ON LAND)
The pH of seawater is between 7.4 and 8.4 making it alkaline.
The amount of a gas that can dissolve in water increases as the temperature of the water decreases. More gas can be dissolved in water under pressure. Cold, bottled soda, which is water, CO2, and flavoring under pressure, will lose its CO2 when the cap is removed and it is no longer under pressure, but the CO2 bubbles continue to rise as the temperature of the soda increases as it stands at room temperature.
Carbon dioxide is known as a "greenhouse gas". The glass in a greenhouse allows solar short-wavelenght infra-red radiation to pass through into the greenhouse. This has a warming effect on the greenhouse. The dirt and all other items in the greenhouse absorb the short IR rays and reradiate long-wavelength IR radiation. Long-wavelength IR radiation, however, will not pass through the greenhouse glass. This keeps the heat in the greenhouse. The same thing happens to automobiles on a sunny day. The automobiles heat up because the long-wavelength can not pass through the glass in the auto.
Carbon dioxide in the atmosphere prevents the re-radiated long-wavelength IR radiation from the earth from leaving our atmosphere. For this reason, as carbon dioxide concentrations in the atmosphere increase the long-wavelength IR radiation remains in the earth's atmosphere resulting in an increase in a climatic temperature increase.
The ocean is a buffer for atmospheric carbon dioxide. This atmospheric gas is readily absorbed into the ocean. The top layers of the oceans, like the atmosphere, contained fairly unwavering concentrations of carbon dioxide for more than 400,000 years. During that span concentrations never rose above 280 parts per million. Current concentrations are approaching 380 parts per million.
If too much CO2 dissolves it will shift the equilibrium and inhibit the formation of the carbonate shells of mollusks and the carbonate skeleton of corals. In addition, the accumulating CO2 entering the ocean will lead to changes in pH or acidity of the upper layers that will be three times greater in magnitude and 100 times faster than those experienced between ice ages.
Recent research, however, indicates that the continued use of fossil fuels will result in more carbon dioxide being dissolved in seawater which in turn will cause the pH of the ocean to become more acidic. In a San Francisco Chronicle article scientists at Lawrence Livermore National Laboratory warn that long-term emissions of carbon dioxide by the world's automobiles, power plants and industries could sharply increase the acidity of the oceans and devastate much of their marine life and that this change may well be irreversible.
These scientists have predicted, using computer modeling, that the change may take only 1,000 years whereas it has taken 300 million years to reach the ocean's current level of acidity.
Burning fossil fuels like coal, oil and natural gas are the cause of increased levels of carbon dioxide in the atmosphere and are considered among the major causes for global warming. Much of the atmospheric CO2 is absorbed and dissolved in the ocean where the dissolved CO2 reacts with water in a series of reactions. When CO2 is added to the ocean in larger and larger amounts, the pH of the ocean will move from its present alkaline state toward a more acidic level.
We already see the results of slightly increased acidity in the bleaching of corals around the world. Corals are very sensitive to changing pH. Increases in the acidity of the ocean will result in significant changes in the lives of oceanic organisms.