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Chapter 6.2

Chapter 6.2. Dissolving and Solubility. Making process of dissolving FASTER!. Many of same things that make chemical reactions go faster – But DISSOLVING IS A PHYSICAL CHANGE , NOT A CHEMICAL CHANGE. Faster dissolving.

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Chapter 6.2

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  1. Chapter 6.2 • Dissolving and Solubility LecturePLUS Timberlake

  2. Making process of dissolving FASTER! • Many of same things that make chemical reactions go faster – • But DISSOLVING IS A PHYSICAL CHANGE, NOT A CHEMICAL CHANGE. LecturePLUS Timberlake

  3. Faster dissolving • When a chunk of something dissolves, you are just pulling it apart into smaller bits (even down to individual molecules or ions) LecturePLUS Timberlake

  4. Faster dissolving • heat • stirring • shaking • smaller chunks (larger surface area) LecturePLUS Timberlake

  5. In a solution, the solute molecules are randomly distributed among the solvent molecules LecturePLUS Timberlake

  6. Figure 15.1: Dissolving of solid sodium chloride. LecturePLUS Timberlake

  7. The solvent is the substance that dissolves the solute to make a solution. The solute is the substance that dissolves in a solution. LecturePLUS Timberlake

  8. Why is water such a great dissolver (solvent) for other substances? LecturePLUS Timberlake

  9. Water is polar... It has a slightly negative “side” by the oxygen atom, and slightly positive “side” by the hydrogens. LecturePLUS Timberlake

  10. Water can dissolve ionic compounds, and covalent compounds that are polar (have “slightly negative” and “slightly positive” parts). LecturePLUS Timberlake

  11. The interaction of polar water molecules with ions LecturePLUS Timberlake

  12. Representation of the polar hydrogen chloride molecule LecturePLUS Timberlake

  13. Chlorine hogs the electron blanket, leaving hydrogen partially, but positively, exposed LecturePLUS Timberlake

  14. Figure 15.3: The ethanol molecule contains a polar O—H bond. LecturePLUS Timberlake

  15. Figure 15.3: The polar water molecule interacts strongly with the polar O—H bond in ethanol. LecturePLUS Timberlake

  16. Soap • The nonpolar side of a soap molecule is “attached” (attracted to) nonpolar grease and oil, the polar side hangs on to the water, and the dirt slips off your hands and is pulled down the drain, trapped, along with the water molecules, by that pesky soap molecule! LecturePLUS Timberlake

  17. (a) non-polar gasoline and non-polar oil mix • polar vinegar and nonpolar oil do not mix • (c) polar water and polar ethyl alcohol mix LecturePLUS Timberlake

  18. Figure 15.6: An oil layer floating on water. LecturePLUS Timberlake

  19. For a more detailed explanation of why polar and nonpolar materials can’t dissolve each other: • http://www.knoxnews.com/kns/science/article/0,1406,KNS_9116_1971484,00.html LecturePLUS Timberlake

  20. Saturated and Unsaturated • A saturated solution contains the maximum amount of solute that can dissolve. Undissolved solute remains. • An unsaturated solution does not contain all the solute that could dissolve LecturePLUS Timberlake

  21. Supersaturated Solutions LecturePLUS Timberlake

  22. To see more of this supersaturation experiment: • http://www.csudh.edu/oliver/demos/supersat/supersat.htm LecturePLUS Timberlake

  23. Crystallization from Supersaturated Solutions of Sodium Acetate Note, you may need to hit “refresh” to get demonstration started and restarted. To see more exciting supersaturation stuff, go to: LecturePLUS Timberlake

  24. Solubility The maximum amount of solute that can dissolve in a specific amount of solvent usually 100 g. g of solute 100 g water LecturePLUS Timberlake

  25. Molarity • Concentration unit of a solution that expresses moles of solute dissolved per liter of solution. • To make a 1 molar solution of a substance, put 1 mole of stuff into a container and add solvent (usually water) up to the “1 liter” mark. LecturePLUS Timberlake

  26. Not this type of Mole LecturePLUS Timberlake

  27. Or this type of Mole LecturePLUS Timberlake

  28. Mole • 6.02 x 1023 is a mole -602,000,000,000,000,000,000 • If you counted paper at the rate of one sheet per second it would take you 19,089,294,774,226,281 years to count a mole of paper. • It is a big number because atoms are small. LecturePLUS Timberlake

  29. A mole of sugar weighs about one half pound but contains how many molecules of sugar? • 602,000,000,000,000,000,000 • 6.02 x 1023 molecules. LecturePLUS Timberlake

  30. Temperature and Solubility of Solids Temperature Solubility (g/100 g H2O) KCl(s) NaNO3(s) 0° 27.6 74 20°C 34.0 88 50°C 42.6 114 100°C 57.6 182 Does the solubility of solids seem to increase or decrease with an increase in the temperature? LecturePLUS Timberlake

  31. A. Why would a bottle of carbonated drink possibly burst (explode) when it is left out in the hot sun ? B.Why would fish die in water that gets too warm? LecturePLUS Timberlake

  32. Solutions A. Gas in the bottle builds up as the gas becomes less soluble in water at high temperatures, which may cause the bottle to explode. B. Because O2 gas is less soluble in warm water, the fish may not obtain the needed amount of O2 for their survival. LecturePLUS Timberlake

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