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Choose to view chapter section with a click on the section heading. The Water Planet

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

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Choose to view chapter section with a click on the section heading. The Water Planet

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

  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 onEarth can’t be used directly fordrinking, irrigation, or industrybecause 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 everywherein the water column. • How does this compare toland 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 pointin any ocean is theChallenger Deep inthe Mariana Trench. The Water Planet Chapter 8 Pages 8-2 to 8-5

  8. Water’s Unique Properties 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 importantmolecules, water is a simplemolecule - it’s chemicalsymbol = H2O. • Consists of three atoms - twohydrogen and one oxygen. • The way it’s held togethergives 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 theformation of molecules. • The hydrogen atoms bondto the oxygen atoms with acovalent bond. • A covalent bond is formed byatoms sharing electrons. Thismakes water a very stablemolecule. In water, the oxygenatom 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 atomshave a net excess positivecharge. • The oxygen atom has anet 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 bondwith adjacent water molecules. • The positively chargedhydrogen end of one watermolecule attracts thenegatively charged oxygenend of another water molecule. • This bond between watermolecules is called ahydrogen bond. Water’s Unique Properties Chapter 8 Pages 8-5 to 8-6

  13. The Polar Molecule • Hydrogen bonds. • Individual hydrogen bonds areweak compared to covalentbonds - only 6% as strong. • Hydrogen bonds can easilybreak 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… “Howimportant is Hydrogen Bondsto your very existence?” Water’s Unique Properties Chapter 8 Pages 8-6 to 8-8

  20. The InorganicChemistry of Water 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 mixtureis 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 hydrogenside of thewater 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 dissolvedinorganic 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 asemi-permeable membrane, such as a cell wall.Because it contains dissolved salts, water in seawaterexists 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 ‰ = 1.80655 x chlorinity ‰ Sample of seawater is tested at 19.2‰ chlorinity: salinity ‰ = 1.80655 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 • pHmeasures acidityor 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 lessthan 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 8.3 - 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 withdepth because the amount of carbon dioxidetends to vary with depth. • Shallow depths have less carbon dioxidewith 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 andthe 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 photosynthesisto 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

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