Unit 15 Power Point


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Unit 15 Power Point

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