Unit 15 Power Point
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Unit 15 Power Point Presentation Transcript

  • 1. Solutions
    Why Does Pasta Expand When Cooked?
    Why does Lemon Juice sting?
    Why Do Salt Grains Dissolve?
  • 2. How Do Solutions Form?
    Polar molecules pull polar molecules apart
    Water molecules break up the salt crystals
  • 3. Polar Molecules
    Salt Crystal
    • Water molecules attracting sodium
  • Some Definitions
    A solution is a mixture of 2 or more substances.
    The substance that dissolves the others is the SOLVENT.
    The substance that dissolve into the solvent are SOLUTES.
    Example: Salt Water
    Water = Solvent Salt = Solute
  • 4.
  • 5. Definitions
    Solutions can be classified as saturated or unsaturated.
    An unsaturated solution contains less than the maximum amount of solute.
    That means you can dissolve more at that particular temperature
  • 6. Definitions
    Solutions can be classified as
    saturatedor unsaturated.
    A saturated solution contains the maximum quantity of solute that dissolves at that temperature.
    If it gets too saturated, crystals will form and drop out of solution.
  • 7. How Temperature Affects Solubility
    More can dissolve in hot fluids than cool fluids.
    That is why you heat water to dissolve sugar or other substances into them.
    At cooler temperatures, the crystals will just drop to the bottom.
    If it is saturated and you cool it down, crystals will drop out of solution.
  • 8. Definitions
    SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved
    Supersaturated solutions are unstableand temporary
    Any disturbance, including shaking, stirring, or adding more solute will cause it to come out of solution.
  • 9. Supersaturated Sodium Acetate
    One application of a supersaturated solution is the sodium acetate
    “heat pack.”
    Click on the metal piece inside and it instantly precipitates
  • 10. Aqueous Solutions
    How do we know ions are present in aqueous solutions?
    ELECTROLYTES
    They conduct electricity
    HCl, MgCl2, and NaCl are strong electrolytes.
    They dissociate completely (or nearly so) into ions.
  • 11. Aqueous Solutions
    Some compounds dissolve in water but do not conduct electricity.
    They are called nonelectrolytes.
    These are usually covalent compounds, not ionic
    Examples include:
    sugar
    ethanol
    ethylene glycol
  • 12. Electrolytes in the Body
    • Carry messages to and from the brain as electrical signals
    • 13. Maintain cellular function.
  • Changing Physical Properties
    On adding a solute to a solvent, the properties of the solvent are modified.
    Vapor pressure decreases
    Melting point decreases
    Boiling point increases
    Osmosis is possible (osmotic pressure)
    They depend only on the NUMBER of solute particles relative to solvent particles, not on the KIND of solute particles.
  • 14. Change in Freezing Point
    Ethylene glycol
    Pure water
    The freezing point of a solution is LOWERthan that of the pure solvent
  • 15. Change in Freezing Point
    Common Applications of Freezing Point Depression
    Ethylene glycol – deadly to small animals
    Propylene glycol
  • 16. Properties of Acids
    • Sour Taste
    • 17. Litmus paper turns red
    • 18. Reactivity with Metals
  • Properties of Bases
    • Bitter Taste
    • 19. Litmus paper turns blue
    • 20. Slippery Feel
    • 21. Corrosive
  • Definitions:
    An acid is a substance that increases the H+ (or H3O+) concentration in an aqueous solution. Also known as proton donors.
    HCl + H2O 
     H++ H2O+ Cl-
    H3O+ + Cl-
    A base is a substance that increases the OH- concentration
    in an aqueous solution. Also known as proton acceptors.
    NaOH(s)  Na+ + OH-
  • 22. pH Scale
  • 23. Why is Sea Water Basic?
    Alkaline substances such as limestone dissolve from rocks, head down rivers, and are deposited in the sea
    Coral, clams, snails, and others make their shells from the calcium dissolved in sea water
  • 24. Ocean Acidification
    The pH of the ocean is becoming more acidic with global warming.
    That is because more CO2 is dissolving into the ocean as more if released by humans into the atmosphere
    This makes it more difficult for sea creates with calcium shells to survive
    Their calcium shells dissolve in the acidic water
    Coral reefs are being destroyed and the ocean ecosystems affected.
  • 25. Acid/Base reactions (neutralization):
    Produce water and a salt (and sometimes carbon dioxide).
    Hint: concentrate on the water first. Remember, water has the formula HOH.
    Complete and balance the following:
    HCl + KOH 
    H2O+ KCl
    HCl + Ca(OH)2
    2
    2HOH + CaCl2
    Require equal numbers