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Chapter 7: Properties of Solutions

Chapter 7: Properties of Solutions. Mixture Review. Mixtures are combos of elements and/or compounds that are physically combined True mixtures can be separated by physical means that do not break or form bonds Mixtures do not exist in a fixed ratio by mass. Classifying mixtures.

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Chapter 7: Properties of Solutions

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  1. Chapter 7:Properties of Solutions

  2. Mixture Review • Mixtures are combos of elements and/or compounds that are physically combined • True mixtures can be separated by physical means that do not break or form bonds • Mixtures do not exist in a fixed ratio by mass

  3. Classifying mixtures • Heterogeneous mixtures: different phases (states of matter), non-uniform, no consistent makeup throughout a sample • Homogeneous mixture: same phase (state of matter), uniform, with a consistent makeup throughout a sample

  4. How can we separate mixtures? • We can separate by physical properties: • Density • Molecular polarity • Freezing point • Boiling point

  5. Techniques for separating heterogeneous mixtures • Pouring off: a separatory funnel is used with non-mixing liquids (different polarities or densities) • Filtration: small particles pass through while larger particles are trapped • Filtrate is what is collected in the filter

  6. Distillation • Used to separate homogeneous mixtures by boiling points • One part boils off, vapor gets cooled and trapped in a separate container

  7. Separation • Particle size: manually separate parts of a mixture based on size • Magnetic separation: remove metallic elements from non-metallic (iron and sulfur)

  8. Chromatography • Separation by attraction

  9. Review Can mixtures be separated by physical means? Do mixtures exist as fixed ratios? How many phases are there in a homogenous mixture? When would you use filtration? When would you use distillation? Describe a procedure that could be used to separate a mixture of sand and table salt.

  10. Aim: How can we describe solutions? • Do Now: Complete mixtures questions on handout, if not done already • Look up definitions for vocabulary page

  11. Solutions(homogeneous mixtures) • Can’t be filtered (extremely small dissolved particles) • Dissolved particles never settle, except when caused by temperature changes or evaporation • Liquid & gas solutions are clear and transparent since dissolved particles can’t be seen • Single phase, even when starting with components of different phases

  12. Parts of a Solution • The solute is the dissolved substance, the smaller portion of the solution • The solvent is the substance in which the solute is dissolved, the larger portion of the solution Solute + Solvent = Solution

  13. Solute & Solvent • 10g of NaCl in 100mL of water • 5mL of CO2 (g) and 20mL O2 (g) in 80mL N2 (g) • 3g of carbon in 97g of iron

  14. Types of Solutions • Gas solutions (air): gases completely dissolved in one another • Liquid solutions: solid, liquid, or gas solutes dissolved in a liquid solvent • Carbonated water (CO2 gas in water) • Salt water (solid salt in water) • Antifreeze (liquid ethylene glycol in water) • Solid solution: mostly solid dissolved in solid, but can be a liquid or gas dissolved in a solid • Alloys of bronze (Cu/Sn) or steel (Fe/C)

  15. Aqueous Solutions Aqueous solutions are solutions in which water is the solvent Given the abbreviation (aq) Ionic compounds break into their oppositely charged parts when they enter aqueous solutions NaCl (s)  Na+ (aq) + Cl- (aq)

  16. Aqueous Solution Examples • Tea (aq) • NaCl (aq) • Ammonia: NH3 (aq) • Hydrochloric acid: HCl (aq) • Sodium hydroxide: NaOH (aq)

  17. Homogeneous mixtures (solutions) Miscible: capable of being mixed One substance dissolves in another Heterogeneous mixtures Immiscible: not capable of mixing Do not dissolve in one another How Can We Describe Mixtures?

  18. Saturated Solutions are in Equilibrium • Solutes dissolve in solvents, but only to a certain point • Solutions with the maximum amount of dissolved solute are saturated solutions • Saturated solutions are in a balanced state of equilibrium

  19. Any extra solid that cannot be dissolved falls out of the solution and crystallizes as a precipitate

  20. In saturated solutions, the system is at equilibrium. The rate of dissolution is equal to the rate of crystallization.

  21. Explaining Molecule-Ion Forces of Attraction in Solution • When ionic compounds mix with water, they form aqueous solutions of dissolved ions • Polar water molecules attract the ions, separating them and dissolving the solid • This is molecule-ion attraction

  22. Explaining Molecule-Ion Forces of Attraction in Solution http://www.youtube.com/watch?v=xdedxfhcpWo&feature=related http://www.youtube.com/watch?v=7PHhBBg-6X0&feature=related

  23. Conclusion Questions • Answer the following questions on paper: • How many phases are there in a homogeneous mixture? • How are substances different from solutions? • How does a solute differ from a solvent in the formation of a solution? • What happens to solute and solvent when ionic compounds like NaCl dissolve in H2O?

  24. How Do You Like Your Tea? • Do Now: Take out notes and Reference Tables • Consider what makes the three cups of iced tea on the front desk different

  25. For Tuesday Trimester Test • Period 3: in this room • Periods 5/6: in this room • Period 9: in Physics room downstairs • HW: print packets from website, finish vocab sheet, hand in labs

  26. Describing Types of Solutions:Unsaturated Solutions • Unsaturated solutions have less than the maximum amount of solute dissolved in them • More solute can still be added and dissolved • Dilute solutions: solute-SOLVENT • 100 seat restaurant with only 40 people seated

  27. Describing Types of Solutions:Saturated Solutions • Saturated solutions have the maximum amount of solute dissolved in them • No more solute can be dissolved in saturated solutions • Concentrated solutions: SOLUTE-solvent • 100 seat restaurant with 100 people seated in it

  28. Describing Types of Solutions:Supersaturated Solutions • Supersaturated solutions have more than the theoretical maximum amount of solute dissolved in them • Rare and unstable, need high temp/pressure • SOLUTE >>> solvent, excess solute will precipitate if solution is agitated • 100 seat restaurant with 120 people in it, then fire marshal comes and throws 20 people out

  29. Rock Candy

  30. Supersaturation video http://www.youtube.com/watch?v=HnSg2cl09PI

  31. Solubility • If a substance is soluble, it can be dissolved in a solvent • Solubility is how much of a solute will dissolve in a certain amount of solvent at a given temperature

  32. How Can We Describe Solutions? • Easy answer: use reference Table G • Up curves are solids • Direct relationship • temp,  solubility • Down curves are gases • Indirect relationship •  temp, solubility

  33. Understanding Solubility Curves • Each line represents a saturated solution of a solute, across a range of temperatures • The higher the point on a line, the more soluble a substance is • Experiments tell us how much solute can be dissolved in 100g of water at a given temp

  34. Remember: points on lines are saturated solutions (at equilibrium). Rate of dissolution = rate of crystallization

  35. Conclusion • Which type of solution can still hold additional solute? • Which type of solution holds the most solute possible? • What must be done to a solution to make it supersaturated? • Which type of solution is represented by any point on a solubility curve?

  36. Homework • Complete review book questions, on separate paper • Page 123, # 13-23

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