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Unit # 11

Unit # 11. Phase Diagrams. What is a Phase Diagram?. A phase diagram shows the preferred physical states of matter at different temperatures and pressure. Triple point is the intersection on a phase diagram between three phases

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Unit # 11

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  1. Unit # 11 Phase Diagrams

  2. What is a Phase Diagram? • A phase diagram shows the preferred physical states of matter at different temperatures and pressure. • Triple pointis the intersection on a phase diagram between three phases • The point at which all three states of a substance are present

  3. Terms to Know • Critical point • The temperature and pressure at which you can no longer tell the difference between a liquid and a gas. • It is where the liquid-gas line stops

  4. Interpreting a Phase Diagram • What is point B? • What is point C?

  5. Phase Change Terms We must know the names of the phase changes. Which ones do we know already?

  6. Changes of State • Solid becomes a liquid • Melting Point • Liquid becomes a solid • Freezing Point • Gas becomes a liquid • Condensation Point • Liquid becomes a gas • Boiling Point

  7. Changes of State • Melting and Freezing Points are the SAME TEMPERATURE • Condensation and Boiling Points are the SAME TEMPERATURE

  8. How do we identify the phases?

  9. Interpreting a Phase Diagram • What is happening as you cross curve AB? • What is happening as you cross curve BC? • What is happening as you cross curve BD?

  10. Let’s interpret the diagrams

  11. Changing Phases • Normal Boiling point • Boiling point of a substance at 1 atm • 1 atm = 760 Torr, 760 mm Hg • Water is 100 0C • Normal Freezing point • Freezing point of a substance at 1 atm • Water is 0 0C

  12. Changing Phases • During a phase change there is no change in temperature – the KE is used to spread or bring together the molecules of the substance • During a phase change there is only a change in potential energy • Heating curve – a plot of temperature versus time for a substance where energy is added at a constant rate

  13. Heating Curve for Water

  14. Vapor Pressure Graphs • Vapor Pressure • Every liquid has molecules evaporating and condensing at all times • Force of the evaporating gas is called vapor pressure • Vapor Pressure Graphs show the boiling point of liquids at different temperatures and pressures

  15. Vapor Pressure Graphs • At what temperature does liquid A boil at a pressure of 500 mm Hg? • At what pressure does liquid B boil at 110°C? • Intermolecular Forces are forces that hold particles together • Which liquid has stronger intermolecular forces?

  16. Solubility Curves • Solvents • The liquid you are dissolving something into (ex. Water) • Solutes • What you are trying to dissolve (ex. Sugar) • Solubility Curves show how many grams of solute you can dissolve in a specific amount of solvent at various temperatures

  17. Solubility Curves • A specific amount of solvent?? How much is that??? • READ THE LABELS ON THE GRAPH!!!!!

  18. Solubility Curves • Which is the most soluble at 10°C? • Which is least soluble at 10°C? • Which becomes less soluble as temperature goes up? • Which solubility changes the least from 0-100°C? • How many grams of KClO3 can dissolve in 100g of water at 70°C? • In 200g of water?

  19. Solubility Curves • Saturated Solution • Contains the maximum amount of solute that can be dissolved at the given temperature • If you have a saturated solution of KClO3 at 70°C, how much will precipitate at 30°C?

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