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chapt10_lecture.ppt
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 |
Sheet1
| drinking and cooking | 2% |
| cleaning dishes | 6% |
| laundry | 11% |
| bathing | 23% |
| toilets | 29% |
| lawn and garden | 29% |
Sheet1
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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