DO NOW What is a solution?

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DO NOWWhat is a solution?

• AGENDA
• Introduction to solutions
• Solutions vocabulary

• REMINDERS

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What do the following pictures have in common?
Air
Salt water
Bronze (copper tin)
They are all solutions A solution is a
homogeneous mixture in a single phase
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Review

• Elementsubstance that cannot be broken down into
  simpler substances (periodic table)
• Compounda substance made of atoms of more than
  one element bound together (H2O, CO2, NaCl)
• Mixturea combination of more than one pure
  substance (Salt water, Powerade, Salad)

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Mixture Review

• Mixturea physical blend of two or more
  substances
• Heterogeneous mixtureone that is not uniform in
  composition
• Homogeneous mixtureone that has a completely
  uniform composition

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Homogenous Mixture

• Homogeneous mixtureone that has a completely
  uniform composition
• Alloy uniform mixture of two metals
• Amalgam (silver mercury), steel (iron carbon)

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Mixture Review
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Mixture REVIEW

• You can separate mixtures by PHYSICAL means
• Distillation
• Separation
• Chromatography

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Polarity

• Polar molecules-
• one end of a molecule is slightly positive and
  the other end is slightly negative
• Unequal sharing of electrons
• Nonpolar molecules-
• charges are equal and cancel out each other
• Equal sharing of electrons

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Water

• Water is a polar molecule!

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p. 398 summary Type Particle size Settle upon standing Tyndall effect (Scatter light)
Solutions Homo-geneous 0.01-1 nm No (cannot be filtered) no
Colloid Hetero-geneous 1-1000 nm No (cannot be filtered) Yes
Suspension Hetero-geneous Greater than 1000 nm Yes (can be filtered) sometimes
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Solution Chemistry

• Solutiona homogeneous mixture
• 1. Solutedissolved particles in a solution
• 2. Solventthe dissolving medium in a solution
  (usually water, the universal solvent)

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Kool-Aid Solution

• Kool-Aid Juice is the SOLUTION
• Kool-Aid powder and Sugar are the SOLUTES
• Water is the SOLVENT

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Solutions are homogeneous mixtures that could be
solid, liquid, or gaseous solute solvent
Gas Gas Oxygen in nitrogen
Gas Liquid CO2 in water
Liquid Gas Water in air
Liquid Liquid Alcohol in water
Liquid Solid Mercury in silver and tin (dental amalgam)
Solid Liquid Sugar in water
Solid Solid Copper in nickel (alloys)
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Soluble vs. Insoluble

• Solubledissolves completely so that solution
  looks transparent (free of any floating particles
• Insolubledoes not dissolve completely solution
  is cloudy

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How does dissolving takes place?

• What happens when salt is dissolved in water?
• NaCl ? Na Cl-

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Complete the dissociation of the following salts

• KCl ?
• MgCl2?
• AlCl3?
• MgF2?

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Complete the dissociation of the following acids

• HCl ?
• HBr?
• HC2H3O2?
• HNO3?

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Solution Chemistry

• Electrolytescompounds that conduct an electric
  current
• ALL ionic compounds NaCl, CuSO4, NaOH
• NonelectrolytesCompounds that do not conduct an
  electric current in either aqueous solution or
  the molten state
• Many molecular (covalent) compounds carbon,
  sugar, alcohol

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Electrolytes vs. Nonelectrolytes
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Electrolytes vs. Nonelectrolytes

• Weak Electrolyteonly a fraction of the solute
  exists as ions partially dissociate
• Strong Electrolytealmost all the solute exists
  as separate ions completely dissociate

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Strong electrolyte in solution.
Weak Electrolyte in solution.
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Electrolytes vs. Nonelectrolytes

• STRONG ELECTROLYTES
• Strong acids (HCl, H2SO4, HNO3, HBr, HI, HClO4)
• Strong bases (NaOH, KOH, etc.)
• WEAK ELECTROLYTES
• Weak acids (Vinegar, acetic acid, CH3COOH)
• Weak bases (Ammonia, NH3)
• NONELECTROLYTES
• Molecular compounds
• Nonmetal bonded to nonmetal

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Electrolytes vs. Nonelectrolytes

• More moles of ions in solutions, the more
  conductivity
• Which salt would give more ions NaCl or MgCl2?
• So, which will conduct electricity more/be a
  better electrolyte?
• Look back at the dissociation reactions and
  determine the better electrolyte.

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Solubility

• Solubilitythe amount that dissolves in a given
  quantity of a solvent at a given temperature to
  produce a saturated solution.
• Solubility is often expressed in grams of solute
  per 100g of solvent

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Water and Solubility?

• REMEMBER water is a POLAR molecule
• Polar means electrons are not spread evenly
  throughout the molecule
• Polar molecules dissolve polar molecules
• Water can dissolve ammonia
• Nonpolar molecules dissolve nonpolar molecules
• Octane (gasoline) can dissolve CO2
• LIKE DISSOLVES LIKE!!!!

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Solution Concentration

• Concentrationthe quantity of solute dissolved in
  a given quantity of solution
• Three ways to describe a solution
• Unsaturated solution
• Saturated solution
• Supersaturated solution

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Solubility

• Unsaturateda solution that contains less solute
  than solvent
• Saturateda solution that contains the maximum
  amount of solute for a given amount of solvent
  at a constant temperature
• Supersaturateda solution that contains more
  solute than it can theoretically hold at a given
  temperature crystals form

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Solubility

• Two liquids are said to be MISCIBLE if they
  dissolve in each other
• Water and ethanol dissolve in each other
• Liquids that are insoluble in each other are
  IMMISCIBLE.
• Oil and water do not dissolve in each other

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MISCIBLE Water and alcohol
IMMISCIBLE Water and oil
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Gas Solubility

• Henrys Lawas the pressure of the gas above the
  liquid increases, solubility of the gas increases
  and vice versa

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Gas Solubility

• Henrys Law
• S solubility
• P Pressure

S1 S2 P1 P2

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Gas Solubility and temperature

• As temperature increases, the solubility of a gas
  tends to decreases.

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Factors Affecting Rate of Dissolving of solid
solutes

• SURFACE AREA
• Solutes with larger surface area dissolves faster
• Smaller pieces larger surface area
• Smaller pieces dissolve faster than larger pieces

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Factors Affecting Rate of Dissolving of solid
solutes

• STIRRING
• Stirring or shaking a solution helps the solute
  dissolve faster
• Stirring or shaking moves dissolved sugar away
  from undissolved sugar crystals

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Factors Affecting Rate of Dissolving of solid
solutes

• TEMPERATURE
• Solid solutes dissolve faster when the solvent is
  hot (except gases !)
• When substance is heated, particles move faster
  causing more collisions between particles

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Solubility Curves

• Solubility curves (graphs) give the solubility
  and temperature of a saturated solution.
• Solubility is on y-axis
• Temperature (C) is on x-axis

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Solubility Curve
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Solubility Curves

• SATURATED solution is ON line or curve
• UNSATURATED solution is BELOW line or curve
• SUPERSATURATED solution is above line or curve

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Colligative Properties

• Properties that depend on the solution
  concentration of solute particles but NOT their
  identity i.e. the addition of ANY solute will
  affect the property (ionic compounds usually more
  of an effect than molecular)

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Colligative Properties - examples

• Vapor Pressure pressure caused by molecules
  that have escaped the liquid phase nonvolatile
  solutes will lower the vapor pressure the
  addition of a solute prevents as many water
  molecules from leaving

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Vapor Pressure, contd

• Volatile Substances will increase vapor pressure
  (volatile means that it evaporates easily
  volatile substances like acetone will increase
  vapor pressure when mixed with water)

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Freezing Point Depression

• Adding a solute to water will LOWER the freezing
  point
• The ocean freezes at -2.2oC because of the added
  salt
• Antifreeze is added to car radiators in the
  winter to prevent from freezing
• Electrolytes have more of an impact than
  non-electrolytes do

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Boiling Point Elevation

• The boiling point is raised when a solute is
  added to water
• Again, electrolytes will affect this more than
  non-electrolytes do

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Precipitation Reactions

• Double Replacement reaction in which an insoluble
  product is formed
• AC BD ? AD(s) BC(aq)