water’s unique properties there are strong forces of attraction between molecules of water....
TRANSCRIPT
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Solutions
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Water’s Unique Properties
• There are strong forces of attraction between molecules of water. Hydrogen bonds
• Water is a polar molecule• Water is amphoteric (can act as both acid &
base)• Water exists as a liquid over a wide temp range. • Liquid water changes temperature slowly. High
specific heat• Liquid water can dissolve a variety of
compounds.• Water expands when it freezes.
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Attraction Between Molecules• There are strong forces of attraction
between molecules of water.• Hydrogen bonds• Result in many distinctive properties
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Liquid state
Exists in liquid state over wide range of temperatures:
32° F to 212° F
This is important because most biological processes require liquid water.
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Unique Role of Water in Biological Systems
It makes up about 70% of the human body
It takes up about 71% of the Earth’s surface.
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• Water is critical to virtually all cellular function– Metabolism– Diffusion– Osmosis– Transport– Reproduction– Lubricant– Volume – Cellular respiration: C6H12O6 + O2 → CO2 + H2O + energy
– Photosynthesis: CO2 + H2O + sunlight → C6H12O6 + O2
Key Role in Biological Systems
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High Heat Capacity
• Water warms & cools slower than surrounding land
• Helps moderate earth’s climate
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Universal Solvent: • Water can dissolve many
substances.• Carry nutrients• flush wastes• distribute particles• facilitate other cycles• Unfortunately, it can
become polluted by water-soluble wastes & transport wastes thru ecosystem
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Expands When Frozen• Ice has a lower density than liquid
water. Thus, ice floats on water.• One of the only exceptions to
thermal expansion
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Surface tension• Surface behaves like
an elastic membrane• Cohesion – water
molecules stick to each other
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Capillary actionLong narrow columns of
water rise through roots to leaves
Adhesion – watermolecules stickto other surface
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What are solutions?• Homogeneous mixtures
containing 2 or more substances called the solute and the solvent.
Solute
• When you look at a solution it is impossible to tell the solute from the solvent
Solvent
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Solutions
• Solute- what is being dissolved• Solvent- the dissolving medium (causes the
dissolving)• Solution- the resulting homogeneous mixture• Aqueous Solution - water is solvent• Dilution – adding more solvent = less concentrated
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Universal Solvent• Water is the most
common solvent among liquid solutions
• H2O is polar, having a slightly positive charge on the hydrogen end and negative charge on the oxygen end.
• Because water is polar it dissolve other polar and ionic compounds
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Dissolution or Solvation of Solid Solute = Dissolving
Happens only on the surfaceWater molecules surround, attract, and pull ions or
molecules into solution
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Like dissolves Like• Polar substances dissolve polar • Nonpolar substances dissolve nonpolar
• Water is polar…which of the above will dissolve in H2O
GlucoseMineral OilIsopropyl Alcohol
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Solubility• Solubility is maximum amount of solute that
will dissolve in solvent at a set of condition• Soluble - A substance that dissolves in a
solvent ex. Salt and water
• Insoluble - A substance that does not dissolve ex. Sand and water
• Miscible – 2 liquids that are soluble• Ex. Alcohol and water
• Immiscible – 2 liquids that aren’t soluble
• Oil and Water
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Factors Affecting Solubility&
Rate of Dissolution (Dissolving)
1. Nature of Solute / Solvent. - Like dissolves like Polar dissolves polar; nonpolar dissolves nonpolar
2. Temperature - affects velocity of particles
3. Pressure4. Agitation = Stirring – disperses particles
5. Surface Area: crushing increases surface area on which dissolving can occur
Sugar cubes vs
Granulated sugar
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Factors Affecting Solubility&
Rate of Dissolution (Dissolving)Solid Solute in Liquid solvent
Gas Solute in Liquid solvent
Ex. Sugar in Tea Ex. CO2 bubbles in soda
Temperature ↑
Pressure ↑
Agitation – ↑ Stirring
Surface Area – ↑ Crush
↑ ↓N/A ↑
↑ ↓
↑ N/A – can’t crush a gas!
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General Solubility Rules• Use STAAR
Chart to determine Which Ionic compounds are soluble and insoluble
• NaNO3
• AgCl• Be3(PO4)2
• Na3PO4soluble
insoluble
soluble
insoluble
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Types of Solutions
1. Electrolytes – ionic compounds dissolve into ionsconducts electric currentthe more ions → stronger current
2. Nonelectrolytes – molecular compounds: stay molecules in solutionno ions → do not conduct current
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Nonelectrolyte Weak electrolyte Strong electrolyte
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Electrolytes in the Body
Carry messages to and from the brain as electrical signals
Maintain cellular function with the correct concentrations
electrolytes
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Types of Solutions1. Saturated Solution: Full2. Unsaturated Solution: not full3. Supersaturated Solution: overly Full, crystals
will form when disturbed
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Saturated Solution• Contains the maximum amount of
dissolved solute for a given amount of solute at at specific temperature
• No more will dissolve• Will be a point on the line of a Solubility
Graph
Ex. NaClO3 at 40°
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Unsaturated solution• contains less dissolved solute for a given
temperature and pressure than a saturated solution
• More can be dissolved• Will be a point under the line on graph
Ex. NaClO3 at 40°
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Supersaturated solution• contains more dissolved solute than a
saturated solution at the same temperature
• Contains more than it should• Will precipitate if disturbed• Will be a point above the line
Ex. NaClO3 at 40°
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Saturated solution to supersaturated solution
• http://www.youtube.com/watch?NR=1&v=1y3bKIOkcmk&feature=fvwp
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Solubility Graph
Determine type of solution:
30 grams of NaCl at 10°C Unsaturated30 grams of K2Cr2O7 at50°C Saturated50 grams of KCl at 40°C Supersaturated
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Concentration of SoluteConcentration of Solute
The amount of solute in a solution is given by its concentration.
Molarity (M) = moles soluteLiters of solution
EX: A liter of solution containing 0.1 mole of solute is a 0.1 M solution
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A 100.5ml intravenous, IV, solution contains 5.10g of glucose (C6H12O6). What is the molarity of this solution?
Mass of solute = 5.10g C6H12O6
Volume of solution = 100.5mlMolarity = ?
1st – calculate the # of moles
180.16g C6H12O6
2nd – convert milliliters into liters (1000 ml = 1 L)
100.5ml = ______________L0.1005
3rd – use formula to solve
Molarity = Moles of solute =
Liters of solution
0.0283
.1005= 0.282M
= 0.0283 mol C6H12O65.10g C6H12O61 mole C6H12O6
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V1M1 = V2M2
Because total # of moles of solute does not change during dilution:
moles in stock solution = moles after dilution, so: Molarity decreases as Volume increases
DilutionQuite often, however, solutions are prepared by diluting a more concentrated solution. For example, if you needed a one molar solution you could start with a six molar solution and dilute it. The number of moles of solute stays the same. You have simply increased the amount of solvent in the solution
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What volume of a 3.0 M KI stock solution would you use to make a 0.50 L of a 1.5M KI solution???
1st : Make a listM1 = 3.0 MV1 = ?V2 = 0.50 LM2 = 1.5 M
Then plug into formula: V1M1 = V2M2
V1 (3.0) = 0.50(1.5)
And solve for V1 = 0.50(1.5) 3.0
= 0.25 L