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Chapter 17 Water and Aqueous Systems

Chapter 17 Water and Aqueous Systems. Liquid Water and Its Properties Water Vapor and Ice Aqueous Solutions Heterogeneous Systems. Water. Make a list of everything you know about water:. Why is this going to hurt?. Ch 17.1 Liquid Water and Its Properties. The Water Molecule

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Chapter 17 Water and Aqueous Systems

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  1. Chapter 17Water and Aqueous Systems • Liquid Water and Its Properties • Water Vapor and Ice • Aqueous Solutions • Heterogeneous Systems

  2. Water • Make a list of everything you know about water:

  3. Why is this going to hurt?

  4. Ch 17.1 Liquid Water and Its Properties • The Water Molecule • Surface Properties • Specific Heat Capacity

  5. The Water Molecule • H2O • Triatomic • O-H Polar Covalent Bond • Oxygen highly electronegative, therefore acquires the slightly negative charge • Bond Angle of 105o • Dipole forces of attraction

  6. Properties due to Hydrogen Bonding • High Surface Tension • Low Vapor Pressure • High Specific Heat Capacity • High Heat of Vaporization • High Boiling Point

  7. Surface Tension • Molecules in a liquid are pulled in all directions due to intermolecular forces • The molecules at the top are only pulled down and to the sides, they are not pulled up. • These molecules tend to tighten up the top

  8. Surfactant • A wetting agent that decreases surface tension of water, soap

  9. Low Vapor Pressure • Hydrogen Bonds hold water molecules together preventing them from entering the vapor phase

  10. Specific Heat Capacity • 4.18J (1 cal) to raise 1g of water 1oC • High due to hydrogen bonding

  11. Water in Space • http://video.google.com/videoplay?docid=-5089084492638545730 • http://video.google.com/videoplay?docid=243028165368764588&q=water+in+space&total=3270&start=0&num=10&so=0&type=search&plindex=9 • http://video.google.com/videoplay?docid=5098206590977878321&q=water+in+space&total=3270&start=10&num=10&so=0&type=search&plindex=1

  12. Chapter 17.2 Water Vapor and Ice • Evaporation and Condensation • Ice

  13. Evaporation • Heat of Vaporization - 2.26kJ of energy is needed to convert 1g of water at 100oC to 1g of steam at 100oC (on your reference table) • How much energy in kJ is required to change 52.3g of water at 100oC to steam at 100oC?

  14. Condensation • 2.26kJ is given off when 1g of steam at 100oC is converted to 1g of water at 100oC • How much energy in kJ is given off to change 12.4g of steam at 100oC to water at 100oC?

  15. Ice • As water cools it behave like most liquids and its density increases. • Once it cools to 4oC, it decreases in density. • Ice has about a 10% greater volume than water. • Ice has a lower density than water, therefore it floats.

  16. Why does ice float?

  17. Heat of Fusion • 334J of energy is needed to convert 1g of ice at 0oC to 1g of water at 0oC (on your reference table) • How much energy in kJ is required to change 21.8g of ice at 0oC to water at 0oC?

  18. Ch 17.3 Aqueous Solutions • Solvents and Solutes • The Solution Process • Electrolytes and Nonelectrolytes • Water of Hydration

  19. Aqueous Solutions • Water with dissolved samples in it

  20. Solvents • The dissolving medium

  21. Solutes • The dissolved particles

  22. Name the Solvent and Solute • Kool Aid

  23. Name the Solvent and Solute • Hot Chocolate

  24. Name the Solvent and Solute • Salt Water

  25. Name the Solvent and Solute • Tea

  26. Solution Process in Three Steps • Step 1 – Separation of solvent molecules, requires energy to break intermolecular forces (ΔH1) • Step 2 – Separation of solute molecules, requires energy to break intermolecular forces (ΔH2) • Step 3 – Solvent and Solute Molecules Mix, may be exothermic or endothermic (ΔH3)

  27. Heat of Solution ΔHsoln • ΔHsoln = ΔH1 + ΔH2 + ΔH3 • ΔHsoln < 0 , exothermic, solution process is favorable • ΔHsoln > 0 , endothermic, solution process is not favorable

  28. Electrolytes • Compounds that conduct an electrical current in an aqueous solution or molten state • All ionic compounds are electrolytes • Barium sulfate conducts electricity in the molten state but not in the aqueous state, WHY? • Insoluble in water

  29. Nonelectrolytes • Compounds that do not conduct an electrical current in an aqueous solution of molten state

  30. Weak Electrolytes • When in solution, only a fraction of the solute exists as ions

  31. Strong Electrolytes • When in solution, most of the solute exists as ions

  32. Water of Hydration (Crystallization) • The water molecules that make up part of a crystal • A compound that contains water of hydration is called a hydrate

  33. Copper(II) Sulfate Pentahydrate – Deep Blue Crystals

  34. Ch 17.4 HeterogeneousAqueous Systems • Suspensions • Colloids

  35. Suspensions • Mixtures from which particles settle out upon standing • The particles are much larger than that of a solution • Heterogeneous • Particles larger than 100nm • Can be filtered

  36. Colloid • Heterogeneous mixtures containing particles that are intermediate in size between suspensions and solutions • Size between 1nm and 100nm • Glue, Jell-O, paint, smoke • Cloudy or milky in appearance when concentrated • Clear or almost clear when they are dilute

  37. Tyndall Effect • Scattering of visible light in all directions • Suspensions can exhibit the Tyndall Effect, solutions never do

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