Exit Choose to view chapter section with a click on the section heading. ►The Water PlanetThe Water Planet ►Water’s Unique PropertiesWater’s Unique Properties ►The Inorganic Chemistry of WaterThe Inorganic Chemistry of Water ►The Organic Chemistry of WaterThe Organic Chemistry of Water ►Chemical Factors That Affect Marine LifeChemical Factors That Affect Marine Life Chapter Topic Menu

MenuPreviousNext The Water Planet Chapter 8 Pages 8-2 to 8-5

MenuPreviousNext The Water Planet nWater covers about 71% of the Earth’s surface. Considering the depth and volume, the world’s ocean provides more than 99% of the biosphere – the habitable space on Earth. nThe vast majority of water on Earth can’t be used directly for drinking, irrigation, or industry because it’s salt water. The Water Planet Chapter 8 Pages 8-2 to 8-5

MenuPreviousNext The Water Planet nAs the population increases, so does the need for water.  Part of the solution to meeting this demand lies in understanding what water is, where it goes, and how it cycles through nature. The Water Planet Chapter 8 Pages 8-2 to 8-5

MenuPreviousNext The Water Planet nThe Hydrologic Cycle. The Water Planet Chapter 8 Pages 8-2 to 8-5

MenuPreviousNext The Water Planet nThe ocean is vast.  Considering depth and volume, the world’s ocean provides more than 99% of the biosphere - the habitable space on Earth.  The entire ocean is a biosphere - organisms live everywhere in the water column.  How does this compare to land animals? The Water Planet Chapter 8 Pages 8-2 to 8-5

MenuPreviousNext The Water Planet nOur ocean on planet Earth averages 3,730 meters (12,238 feet) deep and it contains more than 1.18 trillion cubic kilometers (285 million cubic miles) of water. nThe deepest known point in any ocean is the Challenger Deep in the Mariana Trench. The Water Planet Chapter 8 Pages 8-2 to 8-5

MenuPreviousNext Water’s Unique Properties Chapter 8 Pages 8-5 to 8-8

MenuPreviousNext The Polar Molecule nMolecules are the simplest part of a substance. nCompared to many important molecules, water is a simple molecule - it’s chemical symbol = H 2 O. nConsists of three atoms - two hydrogen and one oxygen. nThe way it’s held together gives it unique properties. Water’s Unique Properties Chapter 8 Pages 8-5 to 8-6

MenuPreviousNext The Polar Molecule nCovalent bonding.  Covalent bonds result in the formation of molecules.  The hydrogen atoms bond to the oxygen atoms with a covalent bond.  A covalent bond is formed by atoms sharing electrons. This makes water a very stable molecule. In water, the oxygen atom shares the electrons of two single-electron hydrogen atoms. Water’s Unique Properties Chapter 8 Pages 8-5 to 8-6

MenuPreviousNext The Polar Molecule nA molecule with positive and negative charged ends has polarity and is called a polar molecule.  Water is a polar molecule.  The two hydrogen atoms have a net excess positive charge.  The oxygen atom has a net excess negative charge. Water’s Unique Properties Chapter 8 Pages 8-5 to 8-6

MenuPreviousNext The Polar Molecule nThe water molecule’s polarity allows it to bond with adjacent water molecules. nThe positively charged hydrogen end of one water molecule attracts the negatively charged oxygen end of another water molecule. nThis bond between water molecules is called a hydrogen bond. Water’s Unique Properties Chapter 8 Pages 8-5 to 8-6

MenuPreviousNext The Polar Molecule nHydrogen bonds.  Individual hydrogen bonds are weak compared to covalent bonds - only 6% as strong.  Hydrogen bonds can easily break and reform. Water’s Unique Properties Chapter 8 Pages 8-5 to 8-6

MenuPreviousNext The Effects of Hydrogen Bonds nBeing a polar molecule, water has these characteristics:  Liquid Water. The most important characteristics of the hydrogen bonds is the ability to make water a liquid at room temperature. nWithout them, water would be a gas - water vapor or steam at room temperature. nHydrogen bonds hold the molecules together, requiring more energy (heat) to form steam. Water’s Unique Properties Chapter 8 Pages 8-6 to 8-8

MenuPreviousNext The Effects of Hydrogen Bonds nBeing a polar molecule, water has these characteristics:  Cohesion/Adhesion. Because hydrogen bonds attract water molecules to each other, they tend to stick together. This is cohesion. Water also sticks to other materials due to its polar nature. This is adhesion.  Example of adhesion - a raindrop clinging to the surface of a leaf. Water’s Unique Properties Chapter 8 Pages 8-6 to 8-8

MenuPreviousNext The Effects of Hydrogen Bonds nBeing a polar molecule, water has these characteristics:  Viscosity. This is the tendency for a fluid (gas or liquid) to resist flow.  Most fluids change viscosity as temperatures change.  The colder water gets, the more viscous it becomes. It takes more energy for organisms to move through it, and drifting organisms use less energy to keep from sinking. Water’s Unique Properties Chapter 8 Pages 8-6 to 8-8

MenuPreviousNext The Effects of Hydrogen Bonds nBeing a polar molecule, water has these characteristics:  Surface Tension. A skin-like surface formed due to the polar nature of water. Surface tension is water’s resistance to objects attempting to penetrate its surface. Water’s Unique Properties Chapter 8 Pages 8-6 to 8-8

MenuPreviousNext The Effects of Hydrogen Bonds nBeing a polar molecule, water has these characteristics:  Ice Floats: as water cools enough to turn from a liquid into solid ice, the hydrogen bonds spread the molecules into a crystal structure that takes up more space than liquid water, so it floats. Water’s Unique Properties Chapter 8 Pages 8-6 to 8-8

MenuPreviousNext The Effects of Hydrogen Bonds nIf ice sank, the ocean would be entirely frozen – or at least substantially cooler – because water would not be able to retain as much heat. nThe Earth’s climate would be colder – perhaps too cold for life. nSo, the question is… “How important is Hydrogen Bonds to your very existence?” Water’s Unique Properties Chapter 8 Pages 8-6 to 8-8

MenuPreviousNext The Inorganic Chemistry of Water Chapter 8 Pages 8-9 to 8-23

MenuPreviousNext The Inorganic Chemistry of Water Chapter 8 Pages 8-9 to 8-11 Solutions and Mixtures in Water nA solution occurs when the molecules of one substance are evenly dispersed among the molecules of another substance. nWater can act as a solvent. (often called the “universal solvent”)  A solvent is the more abundant substance in a solution; usually a liquid. nA solute is the substance being dissolved and is less abundant in the solution. Solutes are usually a solid or gas.

MenuPreviousNext Solutions and Mixtures in Water nA mixture is the combination of two or more substances that are not chemically bonded, and not in fixed proportions to each other.  Two kinds of mixtures: Homogeneous and Heterogeneous. The Inorganic Chemistry of Water Chapter 8 Pages 8-9 to 8-11

MenuPreviousNext Solutions and Mixtures in Water nTwo kinds of mixtures:  Homogeneous - has a uniform appearance throughout. Examples: Milk, fog, sugar and water, smoke, and stirred up dust in the air. nColloid - a homogeneous solution with intermediate particle size between a solution and suspension. Like milk.  Heterogeneous - is not uniform throughout and consists of visibly different substances. Examples: India ink, oil and water, sand and water. nSuspension - a heterogeneous mixture of larger, visible particles that will settle out on standing. Like sand and water. The Inorganic Chemistry of Water Chapter 8 Pages 8-9 to 8-11

MenuPreviousNext Solutions and Mixtures in Water nWater can be part of both homogeneous and heterogeneous mixtures.  Water’s polar nature makes it good solvent.  Regarding salt, let’s examine why water is a good solvent. Salt crystals are held together by ionic bonding. Sodium loses an electron, making it positive. Chlorine gains and electron making it negative. The opposites attract forming salt. The Inorganic Chemistry of Water Chapter 8 Pages 8-9 to 8-11

MenuPreviousNext Solutions and Mixtures in Water nWater dissolves salt.  Water’s charged ends pull apart - dissociate - the salt (sodium chloride - NaCl) crystal.  Sodium and chlorine become charged particles - ions. Salt - sodium chloride - NaCl in its crystal or solid state. The Inorganic Chemistry of Water Chapter 8 Pages 8-9 to 8-11

MenuPreviousNext Solutions and Mixtures in Water nWater dissolves salt.  The positive sodium ion is attracted to the negative oxygen side of the water molecule.  The negative chlorine ion is attracted to the positive hydrogen side of the water molecule. The Inorganic Chemistry of Water Chapter 8 Pages 8-9 to 8-11

MenuPreviousNext Salts and Salinity nSalinity refers to sodium chloride and many other salts dissolved in seawater. nSalinity includes the total quantity of all dissolved inorganic solids in seawater (ions). nDissolved salts includes sodium chloride and everything else. nScientist’s measure salinity in various ways – current method uses how well water conducts electricity. The Inorganic Chemistry of Water Chapter 8 Pages 8-11 to 8-12

MenuPreviousNext Salts and Salinity nSalinity is expressed in parts per thousand (‰). nThe ocean’s average salinity is 35, meaning 35‰ or 35g/kg. nVariations as small as 0.01 are of importance to oceanographers. nThe ocean’s salinity varies from near zero at river mouths to more than 40‰ in confined, arid regions. nThe proportion of the different dissolved salts never change, only the relative amount of water. The Inorganic Chemistry of Water Chapter 8 Pages 8-11 to 8-12

MenuPreviousNext The Colligative Properties of Seawater nColligative properties are properties of a liquid that may be altered by the presence of a solute and are associated primarily with seawater.  Pure water doesn’t have colligative properties. Fresh water, with some solutes, can have colligative properties to some degree.  The strength of the colligative properties depends on the quantity of solute. The Inorganic Chemistry of Water Chapter 8 Page 8-13

MenuPreviousNext The Colligative Properties of Seawater nThe colligative properties of seawater include:  Raised boiling point. Seawater boils at a higher temperature than pure fresh water.  Decreased freezing temperature. As salinity increases, water resists freezing (why salt is put on a road during ice/snow storms). The Inorganic Chemistry of Water Chapter 8 Page 8-13

MenuPreviousNext The Colligative Properties of Seawater nThe colligative properties of seawater include:  Ability to create osmotic pressure. Liquids flow or diffuse from areas of high concentration to areas of low concentration until the concentration equalizes. The Inorganic Chemistry of Water Osmosis occurs when this happens through a semi-permeable membrane, such as a cell wall. Because it contains dissolved salts, water in seawater exists in lower concentration than in fresh water. Chapter 8 Page 8-13

MenuPreviousNext The Colligative Properties of Seawater nThe colligative properties of seawater include:  Electrically conductive. Ability to conduct an electrical current. A solution that can do this is called an electrolyte.  Decreased heat capacity. Takes less heat to raise the temperature of seawater.  Slowed evaporation. Seawater evaporates more slowly than fresh due to the attraction between ions and water molecules. The Inorganic Chemistry of Water Chapter 8 Page 8-13

MenuPreviousNext The Principle of Constant Proportions nIn seawater no matter how much the salinity varies, the proportions of several key inorganic elements and compounds do not change. Only the amount of water and salinity changes.  This constant relationship of proportions in seawater is called the principle of constant proportions.  This principle does not apply to everything dissolved in seawater – only the dissolved salts. The Inorganic Chemistry of Water Chapter 8 Page 6-14

MenuPreviousNext Dissolved Solids in Seawater nNext to hydrogen and oxygen, chloride and sodium are the most abundant chemicals in seawater. The Inorganic Chemistry of Water Chapter 8 Page 8-14

MenuPreviousNext Determining Salinity, Temperature, and Depth nIf you know how much you have of any one seawater chemical, you can figure out the salinity using the principle of constant proportions. nChloride accounts for 55.04% of dissolved solids – determining a sample’s chlorinity is relatively easy. nThe formula for determining salinity is based on the chloride compounds: salinity ‰ = x chlorinity ‰ Sample of seawater is tested at 19.2‰ chlorinity: salinity ‰ = x 19.2‰ salinity ‰ = 34.68‰ The Inorganic Chemistry of Water Chapter 8 Pages 8-14 to 8-16

MenuPreviousNext Determining Salinity, Temperature, and Depth nMost commonly, salinity is determined with a salinometer. It determines the electrical conductivity of the water. nAn important tool to measure the properties of seawater are the Argo floats - an array of 3,000 free-drifting floats. The Inorganic Chemistry of Water Salinometer Argo Float Chapter 8 Pages 8-14 to 8-16

MenuPreviousNext Determining Salinity, Temperature, and Depth nAnother tool is the conductivity, temperature, and depth (CTD) sensor. The CTD profiles temperature and salinity with depth. nAnother less accurate way to determine salinity is with a refractometer. The Inorganic Chemistry of Water CTD Sensor Refractometer Chapter 8 Pages 8-14 to 8-16

MenuPreviousNext nA source of sea salts appears to be minerals and chemicals eroding and dissolving into fresh water flowing into the ocean. nWaves and surf contribute by eroding coastal rock. nHydrothermal vents change seawater by adding some materials while removing others. nScientists think these processes all counterbalance so the average salinity of seawater remains constant. nThe ocean is said to be in chemical equilibrium. The Inorganic Chemistry of Water Chapter 8 Pages 8-16 to 8-18 Why the Seas Are Salty

MenuPreviousNext Salinity, Temperature, and Water Density nMost of the ocean surface has average salinity, about 35‰. Waves, tides, and currents mix waters to make them more uniform. nPrecipitation and evaporation have opposite effects on salinity.  Rainfall decreases salinity by adding fresh water.  Evaporation increases salinity by removing fresh water.  Freshwater input from rivers lowers salinity.  Abundant river input and low evaporation results in salinities well below average. The Inorganic Chemistry of Water Chapter 8 Pages 8-18 to 8-19

MenuPreviousNext Salinity, Temperature, and Water Density nSalinity and temperature also vary with depth.  Density differences causes water to separate into layers.  High-density water lies beneath low-density water. The Inorganic Chemistry of Water Chapter 8 Pages 8-18 to 8-19

MenuPreviousNext Salinity, Temperature, and Water Density nWater’s density is the result of its temperature and salinity characteristics:  Low temperature and high salinity are features of high- density water.  Relatively warm, low-density surface waters are separated from cool, high-density deep waters by the thermocline, the zone in which temperature changes rapidly with depth.  Salinity differences overlap temperature differences and the transition from low-salinity surface waters to high-salinity deep waters is known as the halocline.  The thermocline and halocline together make the pycnocline, the zone in which density increases with increasing depth. The Inorganic Chemistry of Water Chapter 8 Pages 8-18 to 8-19

MenuPreviousNext Salinity, Temperature, and Water Density The Inorganic Chemistry of Water Global Salinity Chapter 8 Pages 8-18 to 8-19

MenuPreviousNext Acidity and Alkalinity npH measures acidity or alkalinity. nSeawater is affected by solutes. The relative concentration of positively charged hydrogen ions and negatively charged hydroxyl ions determines the water’s acidity or alkalinity.  It can be written like this: The Inorganic Chemistry of Water Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext Acidity and Alkalinity nAcidic solutions have a lot of hydrogen ions (H+), it is considered an acid with a pH value of 0 to less than 7. nSolutions that have a lot of hydroxyl ions (OH-) are considered alkaline. They are also called basic solutions. The pH is higher than 7, with anything over 9 considered a concentrated alkaline solution. The Inorganic Chemistry of Water Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext Acidity and Alkalinity The Inorganic Chemistry of Water Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext Acidity and Alkalinity npH can be measured chemically or electronically. nPure water has a pH of 7 - neutral pH. nSeawater pH ranges from 7.8 to mildly alkaline. nOcean’s pH remains relatively stable due to buffering.  A buffer is a substance that reduces the tendency of a solution to become too acidic or alkaline.  Seawater is buffered primarily by carbon dioxide. The Inorganic Chemistry of Water Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext Acidity and Alkalinity nSeawater is fairly stable, but pH changes with depth because the amount of carbon dioxide tends to vary with depth. nShallow depths have less carbon dioxide with a pH around 8.5. nShallow depths have the greatest density of photosynthetic organisms which use the carbon dioxide, making the water slightly less acidic. The Inorganic Chemistry of Water Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext Acidity and Alkalinity nMiddle depths have more carbon dioxide and the water is slightly more acidic with a lower pH.  More carbon dioxide present from the respiration of marine animals and other organisms, which makes water somewhat more acidic with a lower pH. The Inorganic Chemistry of Water Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext Acidity and Alkalinity nDeep water is more acidic with no photosynthesis to remove the carbon dioxide.  At this depth there is less organic activity, which results in a decrease in respiration and carbon dioxide. Mid-level seawater tends to be more alkaline. nAt 3,000 meters (9,843 feet) and deeper, the water becomes more acidic again.  This is because the decay of sinking organic material produces carbon dioxide, and there are no photosynthetic organisms to remove it. The Inorganic Chemistry of Water Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext Acidity and Alkalinity The Inorganic Chemistry of Water The variation of pH and total dissolved inorganic carbon with depth. Chapter 8 Pages 8-20 to 8-22

MenuPreviousNext The Organic Chemistry of Water Chapter 8 Pages 8-23 to 8-30

MenuPreviousNext The Organic Chemistry of Water Chapter 8 Pages 8-23 to 8-24 Biogeochemical Cycles nOrganic chemistry deals mainly with chemical compounds consisting primarily of carbon and hydrogen. nInorganic compounds such as dissolved sea salts account for the majority of dissolved solids in seawater. nDissolved organic elements also interact with organisms on a significant scale.  These elements are crucial to life and differ from the sea salts in several ways.

MenuPreviousNext Biogeochemical Cycles nProportions of organic elements in seawater differ from the proportions of sea salts because:  The principle of constant proportions does not apply to these elements.  These nonconservative constituents have concentrations and proportions that vary independently of salinity due to biological and geological activity. The Organic Chemistry of Water Chapter 8 Pages 8-23 to 8-24

MenuPreviousNext Biogeochemical Cycles nAll life depends on material from the nonliving part of the Earth.  The continuous flow of elements and compounds between organisms (biological form) and the Earth (geological form) is the biogeochemical cycle. The Organic Chemistry of Water Chapter 8 Pages 8-23 to 8-24

MenuPreviousNext Biogeochemical Cycles nOrganisms require specific elements and compounds to stay alive.  Aside from gases used in respiration or photosynthesis, those substances required for life are called nutrients. nThe primary nutrient elements related to seawater chemistry are carbon, nitrogen, phosphorus, silicon, iron, and a few other trace metals. nNot all elements and compounds cycle at the same rate. nThe biogeochemical cycle of the various nutrients affects the nature of organisms and where they live in the sea. The Organic Chemistry of Water Chapter 8 Pages 8-23 to 8-24

MenuPreviousNext Carbon nCarbon is the fundamental element of life. nCarbon compounds form the basis for chemical energy and for building tissues. nThe seas have plenty of carbon in several forms. It comes from:  Carbon dioxide in the air.  Natural mineral sources - such as carbonate rocks.  Organisms - excretion and decomposition. The Organic Chemistry of Water Chapter 8 Pages 8-24 to 8-26

MenuPreviousNext Carbon nCarbon cycle. The movement of carbon between the biosphere and the nonliving world is described by the carbon cycle. The Organic Chemistry of Water Chapter 8 Pages 8-24 to 8-26

MenuPreviousNext Nitrogen nNitrogen is another element crucial to life on Earth. nOrganisms require nitrogen for organic compounds such as protein, chlorophyll, and nucleic acids. nNitrogen makes up about 78% of the air and 48% of the gases dissolved in seawater. The Organic Chemistry of Water Chapter 8 Pages 8-26 to 6-27

MenuPreviousNext Nitrogen nGaseous nitrogen must be converted to a chemically usable form before it can be used by living organisms. nBacteria “fixes” nitrogen from the air into usable compounds - nitrate, nitrite and ammonium. nIn these forms, autotrophs take up the nitrogen and incorporate it into their systems as protein. The Organic Chemistry of Water Chapter 8 Pages 8-26 to 6-27

MenuPreviousNext Nitrogen The Organic Chemistry of Water nThe nitrogen cycle. Bacteria and humans carry out many of the important steps of the nitrogen cycle. The cycle has four stages: Assimilation, Decomposition, Nitrification, Denitrification. Chapter 8 Pages 8-26 to 6-27

MenuPreviousNext Phosphorus and Silicon nPhosphorus is another element important to life because it is used in the ADP/ATP cycle, by which cells convert chemical energy into the energy required for life.  Phosphorus combined with calcium carbonate is a primary component of bones and teeth. The Organic Chemistry of Water Chapter 8 Page 8-28

MenuPreviousNext Phosphorus and Silicon nThe phosphorus cycle. Dissolved phosphorous is carried to the sea by runoff and leaching from land. Phosphorus is used by plants, then recycled through animals until it is released from waste and decay. The Organic Chemistry of Water Chapter 8 Page 8-28

MenuPreviousNext Phosphorus and Silicon nSilicon is used similarly by some organisms in the marine environment (including diatoms and radiolarians) for their shells and skeletons.  Silicon exists in these organisms as silicon dioxide, called silica. The Organic Chemistry of Water Chapter 8 Page 8-28

MenuPreviousNext Iron and Trace Metals nIron and other trace metals fit into the definition of a micronutrient.  Micronutrients are substances essential to organisms in very small amounts.  These are essential to organisms for constructing specialized proteins, including hemoglobin and enzymes. Plants need iron to produce chlorophyll.  Other trace metals used in enzymes include manganese, copper, and zinc. The Organic Chemistry of Water Chapter 8 Page 8-29

MenuPreviousNext Chemical Factors that Affect Marine Life The Organic Chemistry of Water Chapter 8 Pages 8-30 to 8-34

MenuPreviousNext Chemical Factors That Affect Marine Life Diffusion and Osmosis nDiffusion is the tendency for a liquid, gas, or solute to flow from an area of high concentration to an area of low concentration. Chapter 8 Pages 8-30 to 8-32

MenuPreviousNext Diffusion and Osmosis nOsmosis is diffusion through a semipermeable cell membrane. Chemical Factors That Affect Marine Life Chapter 8 Pages 8-30 to 8-32

MenuPreviousNext Diffusion and Osmosis nThis has important implications with respect to marine animals.  Hypertonic - having a higher salt concentration, and the water will diffuse into the cells. What happens when you put a marine fish into fresh water.  Isotonic - when water concentration inside the cell is the same as the surrounding water outside the cell. There is no osmotic pressure in either direction. Marine fish cells are isotonic.  Hypotonic - having a lower salt concentration than the surrounding water. It is what happens when you put a freshwater fish into seawater. Chemical Factors That Affect Marine Life Chapter 8 Pages 8-30 to 8-32

MenuPreviousNext Diffusion and Osmosis Chemical Factors That Affect Marine Life Hypertonic Isotonic Hypotonic Chapter 8 Pages 8-30 to 8-32

MenuPreviousNext Active Transport, Osmoregulators, and Osmoconformers nOsmosis through a semipermeable cell membrane is called passive transport.  Passive transport moves materials in and out of a cell by normal diffusion. Chemical Factors That Affect Marine Life Chapter 8 Pages 8-32 to 8-34

MenuPreviousNext Active Transport, Osmoregulators, and Osmoconformers nThe process of cells moving materials from low to high concentration is called active transport.  Active transport takes energy because it goes against the flow of diffusion. Chemical Factors That Affect Marine Life Chapter 8 Pages 8-32 to 8-34

MenuPreviousNext Active Transport, Osmoregulators, and Osmoconformers nMarine fish that have a regulation process that allows them to use active transport to adjust water concentration within their cells are osmoregulators. Chemical Factors That Affect Marine Life Chapter 8 Pages 8-32 to 8-34

MenuPreviousNext Active Transport, Osmoregulators, and Osmoconformers nMarine organisms that have their internal salinity rise and fall along with the water salinity are osmoconformers. Chemical Factors That Affect Marine Life Chapter 8 Pages 8-32 to 8-34