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Paper2Rubric.docx

Paper 2 Rubric:

· Turn in via blackboard as Microsoft Word (or apache OpenOffice) document (double spaced)

· Click on the available link to view the video

· Must be at least 300 words in length

· Must have the following included in the paper:

· 1) Summary of the video

· 2) Your opinion of whether the video is discussing the topic in a sound scientific way or in a pseudo-scientific way and why you think this

· 3) A short discussion of at least one way the video could have been improved (saying “this video is great the way it is and needs no improvement” does NOT count)

· Note that there is no citation requirement

chapt10_lecture.ppt

Water and solutions

Chapter 10

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Household water

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Chart1

drinking and cooking
cleaning dishes
laundry
bathing
toilets
lawn and garden
Household water usage
0.02
0.06
0.11
0.23
0.29
0.29

Sheet1

drinking and cooking 2%
cleaning dishes 6%
laundry 11%
bathing 23%
toilets 29%
lawn and garden 29%

Sheet1
Household water usage

Sheet2

Sheet3

Water supplies

  • Surface water
  • Streams, lakes and reservoirs
  • Sediment, bacteria, possible pollutants
  • Groundwater
  • Generally cleaner
  • Seepage from waste dumps, agriculture and industry
  • Major pollution problems

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Properties of water

  • Major constituent of living things
  • “Universal solvent”
  • Dissolves most molecules
  • Solid phase less dense than liquid
  • Ice floats!
  • High specific heat
  • Heat retention
  • Climate stabilization
  • High latent heat of vaporization
  • Evaporative cooling
  • Sweating
  • All result from water’s chemical structure

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Structure of water molecules

  • Bent configuration
  • Characterized by polar covalent bonding
  • Polar molecule; dipole
  • Oxygen = negative center; hydrogen end positive
  • Hydrogen bonding between molecules
  • Strong bond between hydrogen of one molecule and fluorine, nitrogen, or hydrogen of another
  • Accounts for many physical properties (ice floating)

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The dissolving process

  • Solution - homogeneous mixture of ions/molecules from two or more substances
  • Dissolving - the process of making a solution
  • Components of a solution
  • Solvent - present in larger amount
  • Solute - component dissolved in solvent
  • Aqueous solution - solid, liquid or gas dissolved in water

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Solutions - further details…

  • Limits of solubility
  • Saturated solutions
  • Insoluble substances, no noticeable dissolving
  • Simple rule: “Like dissolves like”
  • Polar substances
  • Nonpolar substances
  • Fluids: gases and liquids
  • Miscible fluids
  • Can mix in any proportions w/o separating
  • Gases, intermolecular forces small
  • Immiscible fluids
  • Do not mix

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Liquid solvents and solids

  • “Like dissolves like,” again
  • Oil, grease not soluble in water; salt is
  • Ion-polar molecule force
  • Hydration: attraction of crystal surface versus water molecule
  • Soap - provides both polar and nonpolar environments

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Concentration of solutions

  • Concentration - relative amounts of solute and solvent
  • Relative terminology
  • “Concentrated” - large amount of solute
  • “Dilute” - small amount of solute
  • More precise: measurements of concentration

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Solubility

  • Saturation
  • Solute dissolving limit
  • Equilibrium between going in and out of solution
  • Solubility
  • Concentration of saturated solution
  • Depends on temperature
  • Gases: decrease with temperature; increase with pressure

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Properties of water solutions

Electrolytes

  • Solutions of ionic substances
  • Conduct electricity

Nonelectrolytes

  • Nonconductors
  • Sugar and alcohol solutions

Ionization

  • Forming ions from molecules
  • Can occur as polar molecules dissolve in water

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Acids, bases and salts

  • Three classes of electrolyte
  • Important in consideration of environmental quality
  • Hard water - dissolved salts
  • Soil acidity - plant health
  • Water and air pollution - acid rain

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Properties of acids

  • Sour taste
  • Change color of certain materials, e.g. litmus paper turns red
  • React with active metals (magnesium, zinc) to release H
  • Neutralize bases, forming water and salts

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Bases, alkaline substances

  • Bitter taste
  • Reverse color changes caused by acids; litmus turns blue
  • Slippery on the skin; caustic action converting tissue into soluble material
  • Neutralize acids, forming water and salts

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Explaining acid-base properties

  • Acid - proton donor when dissolved in water
  • Base - proton acceptor when dissolved in water
  • Neutralization - result of mixing acids and bases

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Strong and weak acids and bases

  • Strong acids
  • Ionize completely in water
  • Nitric, sulfuric and hydrochloric acids
  • Weak acids
  • Partially ionized
  • Acetic acid (vinegar)
  • Strong bases
  • Completely ionic in water, with hydroxide ions
  • Sodium hydroxide
  • Weak bases
  • Partially ionized
  • Ammonia, magnesium hydroxide

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The pH scale

Pure water weakly ionized

pH

  • Based on concentration of H3O+ ion
  • Power of ten notation expressing H3O+ concentration
  • Neutral solution: pH = 7
  • Adding acid increases H3O+ ion concentration (lowers pH)
  • Adding base increases OH- concentration (raises pH)

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Properties of salts

  • Any ionic compound except those with hydroxide or oxide ions
  • Produced in acid-base neutralization
  • Essential dietary source of electrolytes and minerals

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