1. Section 15.1 Forming Solutions 1.To understand the process of dissolving 2.To learn why certain substances dissolve in water 3.To learn qualitative terms describing the concentration of a solution 4.To understand the factors that affect the rate at which a solid dissolves Objectives

2. Section 15.1 Forming Solutions What is a solution? Solution – homogeneous mixture –Solvent – substance present in largest amount –Solutes – other substances in the solution –Aqueous solution – solution with water as the solvent

3. Section 15.1 Forming Solutions

4. Section 15.1 Forming Solutions A. Solubility Solubility of Ionic Substances Ionic substances breakup into individual cations and anions.

5. Section 15.1 Forming Solutions A. Solubility Solubility of Ionic Substances Polar water molecules interact with the positive and negative ions of a salt.

6. Section 15.1 Forming Solutions A. Solubility Solubility of Polar Substances Ethanol is soluble in water because of the polar OH bond.

7. Section 15.1 Forming Solutions A. Solubility Solubility of Polar Substances Why is solid sugar soluble in water?

8. Section 15.1 Forming Solutions A. Solubility Substances Insoluble in Water Nonpolar oil does not interact with polar water. Water-water hydrogen bonds keep the water from mixing with the nonpolar molecules.

9. Section 15.1 Forming Solutions A. Solubility How Substances Dissolve A “hole” must be made in the water structure for each solute particle. The lost water-water interactions must be replaced by water-solute interactions. “like dissolves like”

10. Section 15.1 Forming Solutions B. Solution Composition: An Introduction The solubility of a solute is limited. –Saturated solution – contains as much solute as will dissolve at that temperature –Unsaturated solution – has not reached the limit of solute that will dissolve

11. Section 15.1 Forming Solutions B. Solution Composition: An Introduction –Supersaturated solution – occurs when a solution is saturated at an elevated temperature and then allowed to cool but all of the solid remains dissolved Contains more dissolved solid than a saturated solution at that temperature Unstable – adding a crystal causes precipitation

12. Section 15.1 Forming Solutions 1. Why do the temps. go from 0 to 100 o C? The normal liquid range for water is from 0 to 100 o C.

13. Section 15.1 Forming Solutions 2. Which is the most soluble at 60 o C? Potassium iodide.

14. Section 15.1 Forming Solutions 3. Which have the same solubility at 80 o C? Sodium chloride and potassium chlorate

15. Section 15.1 Forming Solutions 4. Which changes the most from 0 to 100 o C? Potassium nitrate

16. Section 15.1 Forming Solutions 5. Which changes the least from 0 to 100 o C? Sodium chloride

17. Section 15.1 Forming Solutions 6. What is the solubility of potassium nitrate at 90 o C? 205 g / 100 cm 3 water

18. Section 15.1 Forming Solutions 7. At what temp. does KI have a solubility of 150 g / 100 cm 3 ? about 12 -13 o C

19. Section 15.1 Forming Solutions 8. Is a solution of 140 g NaNO 3 in 100 cm 3 water at 65 o C saturated, unsaturated, or supersaturated? supersaturated

20. Section 15.1 Forming Solutions 9. You have a solution of KClO 4 containing 4 g at 65 o C. How many more grams to make it saturated? About 26 g more (from 4 g up to the line at 30 g)

21. Section 15.1 Forming Solutions 10. A solution at 70 o C contains 200 g of KI. If cooled, when would crystals start forming? At about 42 o C.

22. Section 15.1 Forming Solutions B. Solution Composition: An Introduction Solutions are mixtures. Amounts of substances can vary in different solutions. –Specify the amounts of solvent and solutes –Qualitative measures of concentration concentrated – relatively large amount of solute dilute – relatively small amount of solute

23. Section 15.1 Forming Solutions B. Solution Composition: An Introduction Which solution is more concentrated? 3 / 1= 3 5 /1 = 5

24. Section 15.1 Forming Solutions B. Solution Composition: An Introduction Which solution is more concentrated? 2 / 1 = 2 4 / 2 = 2 EQUAL

25. Section 15.1 Forming Solutions C. Factors Affecting the Rate of Dissolving Surface area – by crushing a solid it creates more surface area Stirring – prevents particles in solution from reattaching to the crystal Temperature – more kinetic energy makes it easier for the particles to break away from the crystal