1. Water’s Unique Properties The Inorganic Chemistry of Water
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The Water Planet
Water’s Unique Properties
The Inorganic Chemistry of Water
The Organic Chemistry of Water
Chemical Factors That Affect Marine Life
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2. The Water Planet
The Water Planet
Chapter 8 Pages 8-2 to 8-5

3. The Water Planet
Water 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.
The 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

4. The Water Planet
As 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

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

6. The Water Planet The 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

7. The Water Planet
Our 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.
The 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

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

9. The Polar Molecule Molecules are the simplest part of a substance.
Compared to many important molecules, water is a simple molecule - it’s chemical symbol = H2O.
Consists of three atoms - two hydrogen and one oxygen.
The way it’s held together gives it unique properties.
Water’s Unique Properties
Chapter 8 Pages 8-5 to 8-6

10. The Polar Molecule Covalent 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

11. The Polar Molecule
A 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

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

13. The Polar Molecule Hydrogen 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

14. The Effects of Hydrogen Bonds
Being 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.
Without them, water would be a gas - water vapor or steam at room temperature.
Hydrogen bonds hold the molecules together, requiring more energy (heat) to form steam.
Water’s Unique Properties
Chapter 8 Pages 8-6 to 8-8

15. The Effects of Hydrogen Bonds
Being 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

16. The Effects of Hydrogen Bonds
Being 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

17. The Effects of Hydrogen Bonds
Being 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

18. The Effects of Hydrogen Bonds
Being 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

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

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

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

22. Solutions and Mixtures in Water
A 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

23. Solutions and Mixtures in Water
Two kinds of mixtures:
Homogeneous - has a uniform appearance throughout. Examples: Milk, fog, sugar and water, smoke, and stirred up dust in the air.
Colloid - 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.
Suspension - 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

24. Solutions and Mixtures in Water
Water 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.
The Inorganic Chemistry of Water
Chapter 8 Pages 8-9 to 8-11
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.

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

26. Solutions and Mixtures in Water
Water 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

27. Salts and Salinity
Salinity refers to sodium chloride and many other salts dissolved in seawater.
Salinity includes the total quantity of all dissolved inorganic solids in seawater (ions).
Dissolved salts includes sodium chloride and everything else.
Scientist’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

28. Salts and Salinity Salinity is expressed in parts per thousand (‰).
The ocean’s average salinity is 35, meaning 35‰ or 35g/kg.
Variations as small as 0.01 are of importance to oceanographers.
The ocean’s salinity varies from near zero at river mouths to more than 40‰ in confined, arid regions.
The 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

29. The Colligative Properties of Seawater
Colligative 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

30. The Colligative Properties of Seawater
The 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

31. The Colligative Properties of Seawater
The 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
Chapter 8 Page 8-13
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.

32. The Colligative Properties of Seawater
The 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

33. The Principle of Constant Proportions
In 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

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

35. Determining Salinity, Temperature, and Depth
If you know how much you have of any one seawater chemical, you can figure out the salinity using the principle of constant proportions.
Chloride accounts for 55.04% of dissolved solids – determining a sample’s chlorinity is relatively easy.
The 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

36. Determining Salinity, Temperature, and Depth
Most commonly, salinity is determined with a salinometer. It determines the electrical conductivity of the water.
An 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
Chapter 8 Pages 8-14 to 8-16
Salinometer
Argo Float

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

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

39. Salinity, Temperature, and Water Density
Most of the ocean surface has average salinity, about 35‰. Waves, tides, and currents mix waters to make them more uniform.
Precipitation 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

40. Salinity, Temperature, and Water Density
Salinity 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

41. Salinity, Temperature, and Water Density
Water’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

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

43. Acidity and Alkalinity
pH measures acidity or alkalinity.
Seawater 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

44. Acidity and Alkalinity
Acidic solutions have a lot of hydrogen ions (H+), it is considered an acid with a pH value of 0 to less than 7.
Solutions 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

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

46. Acidity and Alkalinity
pH can be measured chemically or electronically.
Pure water has a pH of 7 - neutral pH.
Seawater pH ranges from 7.8 to mildly alkaline.
Ocean’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

47. Acidity and Alkalinity
Seawater is fairly stable, but pH changes with depth because the amount of carbon dioxide tends to vary with depth.
Shallow depths have less carbon dioxide with a pH around 8.5.
Shallow 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

48. Acidity and Alkalinity
Middle 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

49. Acidity and Alkalinity
Deep 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.
At 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

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

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

52. Biogeochemical Cycles
Organic chemistry deals mainly with chemical compounds consisting primarily of carbon and hydrogen.
Inorganic compounds such as dissolved sea salts account for the majority of dissolved solids in seawater.
Dissolved 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.
The Organic Chemistry of Water
Chapter 8 Pages 8-23 to 8-24

53. Biogeochemical Cycles
Proportions 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

54. Biogeochemical Cycles
All 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

55. Biogeochemical Cycles
Organisms require specific elements and compounds to stay alive.
Aside from gases used in respiration or photosynthesis, those substances required for life are called nutrients.
The primary nutrient elements related to seawater chemistry are carbon, nitrogen, phosphorus, silicon, iron, and a few other trace metals.
Not all elements and compounds cycle at the same rate.
The 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

56. Carbon Carbon is the fundamental element of life.
Carbon compounds form the basis for chemical energy and for building tissues.
The 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

57. Carbon
Carbon 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

58. Nitrogen Nitrogen is another element crucial to life on Earth.
Organisms require nitrogen for organic compounds such as protein, chlorophyll, and nucleic acids.
Nitrogen 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

59. Nitrogen
Gaseous nitrogen must be converted to a chemically usable form before it can be used by living organisms.
Bacteria “fixes” nitrogen from the air into usable compounds - nitrate, nitrite and ammonium.
In 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

60. Nitrogen
The 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.
The Organic Chemistry of Water
Chapter 8 Pages 8-26 to 6-27

61. Phosphorus and Silicon
Phosphorus 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

62. Phosphorus and Silicon
The 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

63. Phosphorus and Silicon
Silicon 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

64. Iron and Trace Metals
Iron 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

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

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

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

68. Diffusion and Osmosis
This 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

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

70. Active Transport, Osmoregulators, and Osmoconformers
Osmosis 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

71. Active Transport, Osmoregulators, and Osmoconformers
The 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

72. Active Transport, Osmoregulators, and Osmoconformers
Marine 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

73. Active Transport, Osmoregulators, and Osmoconformers
Marine 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