Understanding Solutions: Mixtures, Solubility, and Saturation

1. QOTD – LAST CONTENT

2. Solutions

3. MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be chemically decomposed? Colloids Suspensions Matter Flowchart MATTER yes no Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

4. Pure Substances • A pure substance has a definite composition. • Pure substances can be elements or compounds

5. Mixtures • Combination of 2 or more pure substances. Heterogeneous Not uniform throughout Homogeneous Uniform throughout

6. Solutions Solutions, in chemistry, are homogeneous mixtures of two or more substances. Substance present in largest quantity usually is called the solvent. (liquid or a solid.) Substance present in smallest quantity is said to be dissolved and is called the solute. (gas, a liquid, or a solid.)

7. Concept Check Coke lists as its ingredients as: “carbonated water, high fructose corn syrup and/or sucrose, caramel color, phosphoric acid, natural flavors, caffeine”. What is the solvent? What are the solutes?

8. Types of Solutions • Gaseous solutions – air • Liquid solutions – drinks • Solid solutions – steel or other alloys

9. Miscible liquids can easily dissolve in one another. • Immiscible liquids are not soluble in each other.

10. Miscible and Immiscible Liquids

11. Heterogeneous Mixtures • Suspensions-contain large particles that “settle out” unless constantly stirred/agitated • Colloids-contain intermediate particles between those in solutions and suspensions

12. Suspensions • Heterogeneous Mixture in which the particles in the solvent are so large that they settle out unless the mixture is constantly stirred. IPC-Solutions-Borders

13. Solutions IPC-Solutions-Borders

14. Solutions How does a solid dissolve into a liquid? IPC-Solutions-Borders

15. How Does a Solution Form? • Solvent molecules are attracted to surface ions. • Each ion is surrounded by solvent molecules. Ionic solid dissolving in water IPC-Solutions-Borders

16. dry Dissolution vs reaction • Dissolution is a physical change—you can get back the original solute by evaporating the solvent. • If you can’t, the substance didn’t dissolve, it reacted. Ni(s) + HCl(aq) NiCl2(aq) + H2(g) NiCl2(s) IPC-Solutions-Borders

17. Factors Affecting Solubility • Chemists use the saying “like dissolves like”: • Polar substances tend to dissolve in polar solvents. • Nonpolar substances tend to dissolve in nonpolar solvents. Oil is nonpolar while water is polar. They are immiscible. IPC-Solutions-Borders

18. Rate of Dissolution There are several factors that affect the rate or “how quickly” dissolving occurs. • Heating • Agitating • Increasing Surface Area IPC-Solutions-Borders

19. Saturation IPC-Solutions-Borders

20. Saturation Types saturated • solution containing undissolved solute in equilibrium with the solution unsaturated • solution containing less than the maximum amount of solute supersaturated • solution containing more solute than is normally allowed IPC-Solutions-Borders

21. Degree of saturation • Unsaturated Solution • Less than the maximum amount of solute for that temperature is dissolved in the solvent. • No solid remains in flask. IPC-Solutions-Borders

22. Degree of saturation • Saturated solution • Solvent holds as much solute as is possible at that temperature. • Undissolved solid remains in flask. • Dissolved solute is in dynamic equilibrium with solid solute particles. IPC-Solutions-Borders

23. Saturated Solution IPC-Solutions-Borders

24. Degree of saturation • Supersaturated Solution • Solvent holds more solute than is normally possible at that temperature. • These solutions are unstable; crystallization can often be caused by adding a “seed crystal” or scratching the side of the flask. IPC-Solutions-Borders

25. A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature. An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature. A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature. Sodium acetate crystals rapidly form when a seed crystal is added to a supersaturated solution of sodium acetate. IPC-Solutions-Borders

26. Solubility IPC-Solutions-Borders

27. Solubility of Gases • In general, the solubility of gases in water increases with increasing mass. Why? • Larger molecules have stronger dispersion forces. IPC-Solutions-Borders

28. Gases in Solution • The solubility of liquids and solids does not change appreciably with pressure. • But, the solubility of a gas in a liquid is directly proportional to its pressure. Increasing pressure above solution forces more gas to dissolve. IPC-Solutions-Borders

29. Temperature Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature. IPC-Solutions-Borders

30. Temperature • The opposite is true of gases. Higher temperature drives gases out of solution. • Carbonated soft drinks are more “bubbly” if stored in the refrigerator. • Warm lakes have less O2 dissolved in them than cool lakes. IPC-Solutions-Borders

31. solubility increases with increasing temperature solubility decreases with increasing temperature Temperature and Solubility Solid solubility and temperature IPC-Solutions-Borders

32. Temperature and Solubility Gas solubility and temperature solubility usually decreases with increasing temperature IPC-Solutions-Borders

33. Electrolytes IPC-Solutions-Borders

34. Electrolyte Electrolyte: a substance that dissolves in water to give a solution that conducts electric current • Any soluble ionic compound is an electrolyte • Strong acids are electrolytes IPC-Solutions-Borders