Solutions: Classification, Solubility, and Conductivity

1. Solutions!

2. Matter Pure Substances Mixtures Elements Compounds Homogeneous Mixtures Heterogeneous Mixtures Classification of Matter

3. Heterogeneous Mixtures • See visibly different regions • Granite • Dirt • Cereals • Oil & Vinegar • See a boundary • Ice cube in water

4. Homogeneous Mixtures • Particlesvery small – on atomic scale • Can’t see particles • Can’t sort particles • Can’t get trapped by filter • Can’t scatter light • Particles evenly distributed • Particles do not separate

5. Which is a solution & how do you know? CuSO4(aq)

6. Solution Homogeneous mixture of 2 or more substances in a single physical state (phase)

7. Parts of a Solution • Solute= dissolved substance • Solvent= dispersing medium

8. Identify the solute and solvent in each picture

9. Solute = ? Solvent = ?

10. Hints to identify solute & solvent • Solute: changes phase = substance have less of • Solvent:maintains phase = substance have most of

11. Aqueous Solutions • Wateris solvent • Transition metalsform brightly colored solutions

12. Solute Solvent Example Gas Gas Air Liquid Gas Water Vapor in Air Solid Gas Mothballs Gas Liquid Seltzer Water Liquid Liquid Antifreeze in radiator Solid Liquid Salt water Gas Solid H2 in Pd metal Liquid Solid Fillings: Hg in Ag Solid Solid Alloys: Brass, etc. Solutions occur in all 3 phases!

13. Gas dissolved in a solid

14. CO2 in and out of water Bubbles mean it’s a mixture not a solution!

15. Alloys Alloys

16. Soluble Soluble – capable of being dissolved A substance that dissolves in another substance issoluble in that substance

17. Insoluble A substance that does not dissolve in another substance

18. Amounts that can dissolve • Solubility =maximum amount of substance that will dissolve in given amount of another substance • LIMITSto amounts of most liquid/solid solutes that will dissolve in given solvent • Temperatureandpressureaffect solubility

19. 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

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

21. Equations for Dissolving C6H12O6(s) + H2O(l) C6H12O6(aq) NaCl(s)+H2O(l)  Na+1(aq) + Cl-1(aq)

22. source Covalent substances dissolve to produce molecules in solution

23. Ionic substances dissolve to produce ions in solution

24. 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

25. Hydration Specific name for solvent-solute interaction when solvent is water

26. Hydration of chloride ion Also called: molecule-ion interaction

27. Molecule-ion interaction Solute-solvent interaction must be greater than: interaction between solute particles for dissolving to occur

28. Solvation in different systems.

29. Solubility • Amount solute that will dissolve in specific solvent at givenTEMPERATURE and PRESSURE • Amount can be determined experimentally • Units: grams solute per 100 grams solvent

30. Solubility Curves of Selected SOLIDS Solubility traces for most but not all solids have (+)’ve slopes; The hotter the solvent, the more solute dissolves

31. Solubility Curves of Selected GASES Solubility traces for all gases have (–)’ve slopes Why do fish like cold water?

32. Why do you see bubbles form on the side of the beaker as the water warms up? (Note: it’s not hot enough to boil)

33. 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

34. Oil & H2O are immiscible

35. Matter Mixtures Pure Substances Homogeneous Mixtures = Solutions Elements Compounds Heterogeneous Mixtures Conduct current Nonconductor Types of Solutions

36. Electricity • What do you need to conduct electricity? Mobile, charged particles!!!!

37. Vocabulary Interlude • Electrolyte: • substancethat 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 moleculesin solution

38. Electrolyte vs. Nonelectrolyte Which solution conducts a current?

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

40. Which solution is most dilute? The most concentrated? How do you know? Thestrongerthecolor, themore concentratedthe solution

42. It’s the same! Which solution is more concentrated? More dilute? What can you say about the #of solute particlesin pictures b and c?

43. Unsaturated Solution Less solutethan maximum amountthat willdissolveat given temperature and pressure

44. Saturated Solution • No more solute will dissolve at given temperature & pressure • Solubility = amount of solute required to form a saturated solution

45. The solution is saturated when the solute stops dissolving

46. Dynamic Equilibrium = Saturated Solution Microscopic level: Rate of dissolving = Rate of recrystallization Macroscopic level:No apparent change

47. Supersaturated Solution • Containsmoresolute than saturated solution • VERY unstable • have to be clever to make these (need to use heat)

48. Testing for saturation: Tosscrystalof soluteinto solutionand see what happens

49. 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

50. What kind of solution was this?