1. I. The Nature of Solutions (p. 401 - 410, 425 - 433)

2. Classification of Matter Solutions are homogeneous mixtures

3. Solute A solute is the dissolved substance in a solution. A solvent is the dissolving medium in a solution. Solvent Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Water in salt waterWater in soda Dental filling

4. Solution = Solute + Solvent Solute - g ets dissolved Solvent- does the dissolving –A–Aqueous (water) –T–Tincture (alcohol) –A–Amalgam (mercury) –O–Organic Polar Non-polar Dental filling Nightmare on White Street Chem Matters, December 1996

6. Solvents Solvents at the hardware store

7. Suspensions and Colloids Suspensions and colloids are NOT solutions. Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred. Colloids: The particle is intermediate in size between those of a suspension and those of a solution.

8. Types of Colloids ExamplesDispersing Medium/ major comp Dispersed Substance/ Minor comp Colloid Type Fog, aerosol spraysGasLiquidAerosol Smoke, airborne bacteriaGasSolidAerosol Whipped cream, soap sudsLiquidGasFoam Milk, mayonnaiseLiquid Emulsion Paint, clays, gelatinLiquidSolidSol Marshmallow, StyrofoamSolidGasSolid foam Butter, cheeseSolidLiquidSolid emulsion Ruby glassSolid Solid sol

9. The Tyndall Effect Colloids scatter light, making a beam visible. Solutions do not scatter light. Which glass contains a colloid? solution colloid

11. The ammeter measures the flow of electrons (current) through the circuit.  If the ammeter measures a current, and the bulb glows, then the solution conducts.  If the ammeter fails to measure a current, and the bulb does not glow, the solution is non-conducting. Electrolytes vs. Nonelectrolytes

12. An electrolyte is: A substance whose aqueous solution conducts an electric current. A nonelectrolyte is: A substance whose aqueous solution does not conduct an electric current. Try to classify the following substances as electrolytes or nonelectrolytes… Definition of Electrolytes and Nonelectrolytes

13. 1.Pure water 2.Tap water 3.Sugar solution 4.Sodium chloride solution 5.Hydrochloric acid solution 6.Lactic acid solution 7.Ethyl alcohol solution 8.Pure sodium chloride Electrolytes?

14. ELECTROLYTES:NONELECTROLYTES: Tap water (weak) NaCl solution HCl solution Lactate solution (weak) Pure water Sugar solution Ethanol solution Pure NaCl But why do some compounds conduct electricity in solution while others do not…? Answers to Electrolytes

15. B. Solvation Solvation – the process of dissolving solute particles are separated and pulled into solution solute particles are surrounded by solvent particles

16. Solvation Strong Electrolyte Non- Electrolyte solute exists as ions only - + salt - + sugar solute exists as molecules only - + acetic acid Weak Electrolyte solute exists as ions and molecules DISSOCIATIONIONIZATION http://www.mhhe.com/physsci/chemistry/animations/chang_2e/molecular_view.swf

17. Solvation NONPOLAR POLAR “Like Dissolves Like”

18. Solvation Soap/Detergent –polar “head” with long nonpolar “tail” –dissolves nonpolar grease in polar water

19. Solubility –maximum grams of solute that will dissolve in 100 g of solvent at a given temperature –varies with temp –based on a saturated soln

20. Factors Affecting Solubility  The solubility of MOST solids increases with temperature.  The rate at which solids dissolve increases with increasing surface area of the solid.  The solubility of gases decreases with increases in temperature.  The solubility of gases increases with the pressure above the solution.

21. Therefore… Solids tend to dissolve best when: o Heated o Stirred o Ground into small particles Liquids tend to dissolve best when: o The solution is cold o Pressure is high

22. Saturation of Solutions  A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated.  A solution that contains less solute than a saturated solution under existing conditions is unsaturated.  A solution that contains more dissolved solute than a saturated solution under the same conditions is supersaturated.

23. Solubility SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration

24. Solubility Solids are more soluble at... –high temperatures. Gases are more soluble at... –low temperatures & –high pressures (Henry’s Law). –EX: nitrogen narcosis, the “bends,” soda

25. Solubility Solubility Curve –shows the dependence of solubility on temperature

26. Solubility Chart

27. Calculations of Solution Concentration Concentration - A measure of the amount of solute in a given amount of solvent or solution Molarity - moles of solute divided by the volume of solution in liters Parts per million – the ratio of parts (mass) of solute to one million parts (mass) of solution Grams per liter - the mass of solute divided by the volume of solution, in liters Percent composition - the ratio of one part of solute to one hundred parts of solution, expressed as a percent

28. A. Concentration Describing Concentration –% by mass - medicated creams (V/V, m/V, W/W) 1.% V/V = 4.1 L / 55 L = 7.5% V/V 2.% W/V = 16 g / 50 mL = 32% W/V 3.% W/W = 1.7 g / 35.0 g = 4.9% W/W –% by volume - rubbing alcohol –ppm, ppb - water contaminants 8 ppm = 8 _ / 1 L, the units should be 1 million times smaller than 1L (or 1kg): 8ppm = 8 mg/L so the mass in 1 L is 8 mg. –molarity - used by chemists –molality - used by chemists

29. B. Molality mass of solvent only 1 kg water = 1 L water

30. C. Dilution Preparation of a desired solution by adding water to a concentrate. Moles of solute remain the same.

31. Concentrated vs. Dilute

32. D. Preparing Solutions 500 mL of 1.54M NaCl 500 mL water 45.0 g NaCl –mass 45.0 g of NaCl –add water until total volume is 500 mL –mass 45.0 g of NaCl –add 0.500 kg of water 500 mL mark 500 mL volumetric flask 1.54m NaCl in 0.500 kg of water

33. D. Preparing Solutions Copyright © 1995-1996 NT Curriculum Project, UW-Madison (above: “Using your hand as a stopper”)

34. D. Preparing Solutions 250 mL of 6.0M HNO 3 by dilution –measure 95 mL of 15.8M HNO 3 95 mL of 15.8M HNO 3 water for safety 250 mL mark –combine with water until total volume is 250 mL –Safety: “Do as you oughtta, add the acid to the watta!”

35. C. Calculations How many grams of solute are present in 1.5 L of 0.24 M Na 2 SO 4 ? V= 1.5 L M=0.24M M = mol of solute per liter of solution WORK: mol = mass ÷ molar mass GIVEN: Mass = ? Molar mass = 142 g/mol 0.24 = mass/142 1.5 L Mass = 0.24 (1.5)(142) =