Solutions!

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Solutions!
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Classification of Matter
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Heterogeneous Mixtures

• See visibly different regions
• Granite
• Dirt
• Cereals
• Oil Vinegar
• See a boundary
• Ice cube in water

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Homogeneous Mixtures

• Particles very small on atomic scale
• Cant see particles
• Cant sort particles
• Cant get trapped by filter
• Cant scatter light
• Particles evenly distributed
• Particles do not separate

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CuSO4(aq)
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Solution

• Homogeneous mixture of 2 or more substances in a
  single physical state (phase)

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Parts of a Solution

• Solute dissolved substance
• Solvent dispersing medium

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Identify the solute and solvent in each picture
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Hints to identify solute solvent

• Solute changes phase
• substance have less of
• Solvent maintains phase
• substance have most of

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Aqueous Solutions

• Water is solvent
• Transition metals form brightly colored solutions

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Solutions occur in all 3 phases!
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CO2 in and out of water
Bubbles mean its a mixture not a solution!
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Alloys
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Soluble

• Soluble capable of being dissolved
• A substance that dissolves in another substance
  is soluble
• in that substance

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Insoluble

• A substance that does not dissolve in another
  substance

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Amounts that can dissolve

• Solubility maximum amount of substance that
  will dissolve in given amount of another
  substance
• LIMITS to amounts of most liquid/solid solutes
  that will dissolve in given solvent
• Temperature and pressure affect solubility

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Factors that affect the rate of dissolving

• Rate of dissolving is different from amount that
  will dissolve!
• Rate is how fast
• factors influence rate of dissolving
• Temperature
• Stirring or Agitation
• Surface Area of Solute
• Amount of solute already dissolved

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Dissolving

• Dissolving is physical change
• All physical chemical changes are accompanied
  by changes in energy

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Equations for Dissolving

• C6H12O6(s) H2O(l)? C6H12O6(aq)
• NaCl(s)H2O(l) ? Na1(aq) Cl-1(aq)

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Covalent substances dissolve to produce molecules
in solution
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Ionic substances dissolve to produce ions in
solution
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Solvation

• Interaction between solvent molecules and solute
  particles
• Solute particles surrounded by solvent particles
  in dissolving process
• Solute particles may be ions, polar molecules, or
  nonpolar molecules
• Solvent molecules may be polar or nonpolar

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Hydration

• Specific name for solvent-solute interaction when
  solvent is water

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Hydration of chloride ion Also called
molecule-ion interaction
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Solute-solvent interaction must be greater than
interaction between solute particles
for dissolving to occur
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Solubility

• Amount solute that will dissolve in specific
  solvent at given TEMPERATURE and PRESSURE
• Amount can be determined experimentally
• Units
• grams solute per 100 grams solvent

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Why do you see bubbles form on the side of the
beaker as the water warms up? (Note its not
hot enough to boil)
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Vocabulary Interlude

• Miscible two liquids that WILL MIX
• together in any amounts
• Water and ethanol are miscible in all proportions
• Immiscible Liquids that will NOT MIX
• Oil and water are immiscible

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Types of Solutions
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Electricity

• What do you need to conduct electricity?

Mobile, charged particles!!!!
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Vocabulary Interlude

• Electrolyte
• substance that dissolves in water to form
  solution that conducts electricity
• ions in solution
• Nonelectrolyte
• substance that dissolves in water to form
  solution that does not conduct electricity
• neutral molecules in solution

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Dilute vs. Concentrated

• Tells relative amount of solute in solvent
• Concentrated
• large amounts of solute
• Dilute
• small amounts of solute

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Which solution is most dilute? The most
concentrated? How do you know?
The stronger the color, the more concentrated the
solution
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Which solution is more concentrated? More
dilute? What can you say about the of solute
particles in pictures b and c?
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Unsaturated Solution

• Less solute than maximum amount that will
  dissolve at given temperature and pressure

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Saturated Solution

• No more solute will dissolve at given temperature
  pressure
• Solubility amount of solute required to form a
  saturated solution

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The solution is saturated when the solute stops
dissolving
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Dynamic Equilibrium Saturated Solution
Microscopic level Rate of dissolving Rate of
recrystallization Macroscopic level No
apparent change
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Supersaturated Solution

• Contains more solute than saturated solution
• VERY unstable
• have to be clever to make these (need to use heat)

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Testing for saturation

• Toss crystal of solute into solution and see
  what happens

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3 possible results
Unsaturated solution

• Crystal dissolves
• Crystal sinks to bottom of solution
• Bam! Suddenly have lots of solid solute in
  beaker

Saturated solution
Supersaturated solution
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How do terms saturated, unsaturated
supersaturated fit in with the solubility curves?

• Saturated solutions have maximum solute that will
  dissolve at given temperature
• Any point on trace lines represent saturated
  solutions
• All points above trace lines represent
• supersaturated solutions
• All points below trace lines represent
• unsaturated solutions

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Characterize points A, B, C, D with respect to
the KNO3 trace using the terms dilute
concentrated, saturated, unsaturated, or
supersaturated
A,C concentrated supersaturated
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Summary of Dissolving

• Occurs at surface of solid
• Involves interaction between solute and solvent
• Interaction is called solvation
• If water is solvent, interaction is called
  hydration
• Involves changes in energy

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Solubility Information

• Often presented in graphs
• Graph show number grams of substance that can
  dissolve in water between 0oC and 100oC
• Trace line represents saturated solution
• above trace line represents supersaturated
  solutions
• below trace line represents unsaturated solutions

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Solubility Graphs

• Traces have positive or negative slopes
• Most solids have positive slope
• the hotter the water, the more solute dissolves
• The colder the water, the less solute dissolves
• All gases have negative slope
• the hotter the water, the less gas dissolves
• The colder the water, the more gas dissolves