Molecular Mixing

1. Molecular Mixing Chapter 7

2. Non-bonding versus Bonding Forces • Which of the following attractive forces would be the greatest: • Ionic • Covalent • Hydrogen bonding

3. Essential Questions • What are the forces that attract molecules to one another? • What happens when a solid dissolves into a liquid? • What determines how much of a solid will dissolve?

4. Essential Questions • How does temperature affect how much solid dissolves? • What about when gases dissolve in liquids? • How does soap work? • What does “hard water” mean? • How does a water softener work?

5. What are the forces that attract molecules to one another? • In pure liquids the forces are: • Dipole-dipole (in polar liquids) • Induced dipole-induced dipole (in nonpolar liquids).

6. Think, Pair, Share • An example of an electrostatic attraction would be • Iron fillings to a magnet • Piece of paper to the floor • Dust clinging to a mirror

7. Polar liquids • dipole – dipole attractions are the electrostatic attractions between the positive side of one molecule and the negative side of another molecule.

9. Nonpolar Liquids • Induced dipole-induced dipole attractions are the weak attractions created by temporary dipoles in nonpolar molecules causing (inducing) a weak temporary dipole in a nearby molecule.

10. Practice Pages • Induced dipole-induced dipole attraction

14. How does Teflon work?

15. Think, Pair, Share • Which of the two following molecules has a greater attraction to itself? Why? • There are more hydrogen atoms. • It is a bigger molecule with more electrons. • There are more individual induced-dipole, induced-dipole attractions.

17. Practice Pages • Attraction in mixtures

18. Attractions in Mixtures • ion – dipole

20. Attractions in Mixtures • dipole - induced dipole • These forces come about when the presence of a polar molecule induces (causes) a dipole to form in a nearby nonpolar molecule.

22. Strength of Molecular Mixing

23. Solutions – Key Ideas Single-phase homogeneous mixture can be gas, liquid, or solid solvent and solute Concentration unsaturated vs saturated solubility

24. Solutions are Mixtures • A physical blend of two or more substances. • Composition of mixtures can vary.

25. Solutions are Homogeneous Mixtures • Homogeneous Mixtures (Solutions) • Uniform throughout the sample • Examples • Kool-Aid • Gasoline

26. Liquid, Gas, or Solid • Air is a mixture of nitrogen, oxygen, carbon dioxide, and a few other gases. • Alloys, like 14K gold, steel, or dental fillings, are mixtures of metals. • Gasoline and rubbing alcohol are mixtures of liquids. • All of these are solutions.

27. Why do Solids Dissolve • Solids dissolve when the attractive forces between the solvent and solute molecules exceed the attractive forces between the solute molecules.

30. Important Concept • It is important to realize that when a solid like sugar is added to water: • It may appear as if it has disappeared

31. Think, Pair, Share • Adding sugar to a 500 mL container of water will cause: • The volume to stay the same • The volume to decrease • The volume to increase

32. Concentration • Concentration is • It is how much _______ there is in a specified ______of solution.

33. Concentration Units • Concentrations are often • for example: • remember, the volume is the volume of _______, not the volume of _______.

34. Concentration Units • concentrations can be expressed as the number of molecules of solute per volume of solution. • For this, we use a unit called the mole. • A mole is 6.02 x 1023 things. (Just like a dozen is 12 things.)

35. Molar Concentrations • Chemists often express concentrations in • M • If I dissolve 6.02 x 1023 molecules of sucrose into one liter of solution

36. Molar Concentrations • 1.00 moles of sucrose weighs 342 grams, so if I dissolved 342 grams into enough water to make 1.00 liters of solution it would be 1.00 M.

38. Molar Concentrations • If I dissolved 684 grams of sucrose into 1.00 liters of solution it would be 2.00 M. • M1 = M2 ; g1 = g2 L1 L2 • What is the molarity if I dissolve 34.2 grams of sucrose into 1.00 liters of solution?

39. Solubility • Solubility is:

40. Saturated / Unsaturated • Saturated – • Unsaturated –

43. Concentration Calculations • If I dissolve 85 grams of baking soda in water to make 1.0 liter of solution, what is my concentration? • If I dissolved 200 g of baking soda in water to make 2.0 liters of solution, what is my concentration?

44. If I have 75 grams of sucrose and want to make a solution with a concentration of 125 g/liter, how much solution can I prepare? • If I want to make 500 mL of sucrose solution with a concentration of 250 g/L, how much sucrose do I need?

45. 1.0 moles of NaOH weighs 40.0 grams. • What weight of NaOH do I need to make 200 mL of solution with a concentration of 2.0 M?

46. Effect of Temperature on Solubility • For most solids and liquids, solubility _________as temperature _______.

49. Soda Stream • How does it work? • What allows the gas to dissolve in the liquid?

50. Effect of Temperature on Solubility • For gases dissolved in liquids, solubility __________as temperature increases. • For gases dissolved in liquids, solubility __________as pressure increases.