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Water

Water. Colorless, odorless, and tasteless Density of ice < than density of liquid water Water expands when it freezes Ice floats on water Density of liquid water = 1.00 g/mL Density of ice = 0.917 g/mL. Water (cont.). Freezes at 0°C Boils at 100°C at 1.00 atm pressure

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Water

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  1. Water • Colorless, odorless, and tasteless • Density of ice < than density of liquid water • Water expands when it freezes • Ice floats on water • Density of liquid water = 1.00 g/mL • Density of ice = 0.917 g/mL Chapter 6

  2. Water (cont.) • Freezes at 0°C • Boils at 100°C at 1.00 atm pressure • Boiling point increases as atmospheric pressure increases • Temperature stays constant during a state change • Relatively large amounts of energy needed to melt solid or boil liquid Chapter 6

  3. Water (cont.) Chapter 6

  4. Structures of the States of Matter Chapter 6

  5. Solutions • Homogeneous mixture of two or more substances • Solute – what is being dissolved • Solvent – what is doing the dissolving • Aqueous solutions – water is solvent Chapter 6

  6. Solubility • Soluble: an appreciable quantity dissolves • Insoluble: very little, if any, quantity dissolves • Dilute solution: little solute in a lot of water • Concentrated solution: lots of solute in the solvent Chapter 6

  7. Solutions (cont.) Chapter 6

  8. Will It Dissolve In Water? • ions are attracted to polar solvents • many ionic compounds dissolve in water • polar molecules are attracted to polar solvents • table sugar, ethyl alcohol and glucose all dissolve well in water • nonpolar molecules are attracted to nonpolar solvents • b-carotene, (C40H56), is not water soluble; it dissolves in fatty (nonpolar) tissues • many molecules have both polar and nonpolar structures – whether they will dissolve in water depends on the kind, number and location of polar and nonpolar structural features in the molecule Tro's Introductory Chemistry, Chapter 13

  9. Salt Dissolving in Water Tro's Introductory Chemistry, Chapter 13

  10. Solvated Ions When materials dissolve, the solvent molecules surround the solvent particles due to the solvent’s attractions for the solute. The process is called solvation. Solvated ions are effectively isolated from each other. Tro's Introductory Chemistry, Chapter 13

  11. Solubility • there is usually a limit to the solubility of one substance in another • gases are alwayssoluble in each other • two liquids that are mutually soluble are said to be miscible • alcohol and water are miscible • oil and water are immiscible • the maximum amount of solute that can be dissolved in a given amount of solvent is called the solubility Tro's Introductory Chemistry, Chapter 13

  12. Why do we do that? • we spread salt on icy roads and walkways to melt the ice • we add antifreeze to car radiators to prevent the water from boiling or freezing • antifreeze is mainly ethylene glycol • when we add solutes to water, it changes the freezing point and boiling point of the water Tro's Introductory Chemistry, Chapter 13

  13. Colligative Properties • the properties of the solution are different from the properties of the solvent • any property of a solution whose value depends only on the number of dissolved solute particles is called a colligative property • it does not depend on what the solute particle is • the freezing point, boiling point and osmotic pressure of a solution are colligative properties Tro's Introductory Chemistry, Chapter 13

  14. Drinking Seawater Because seawater has a higher salt concentration than your cells, water flows out of your cells into the seawater to try to decrease its salt concentration. The net result is that, instead of quenching your thirst, you become dehydrated. Tro's Introductory Chemistry, Chapter 13

  15. Osmotic Pressure Solvent flows through a semipermeable membrane to make the solution concentration equal on both sides of the membrane. The pressure required to stop this process is the osmotic pressure. Tro's Introductory Chemistry, Chapter 13

  16. Hemolysis & Crenation red blood cell in hypotonic solution – water flows into the cell – eventually causing the cell to burst red blood cell in hypertonic solution – water flows out of the cell – eventually causing the cell to distort and shrink normal red blood cell in an isotonic solution Tro's Introductory Chemistry, Chapter 13

  17. Measurement of Solubility • Molarity (M): amount of solute, in moles, per liter of solution Chapter 6

  18. Exercise 6.18A Calculate the molarity of a solution that has 0.0400 mol of NH3 in 5.75 L of solution. Calculate the molarity of a solution made by dissolving 0.650 mol of H3PO4 in enough water to produce 775 mL of solution. Example 6.18 Calculate the molarity of a solution made by dissolving 3.50 mol of NaCl in enough water to produce 2.00 L of solution. Chapter 6

  19. Exercise 6.19 Calculate the molarity of each of the following solutions: Example 6.19 What is the molarity of a solution in which 333 g of potassium hydrogen carbonate is dissolved in enough water to make 10.0 L of solution? a. 18.0 mol of H2SO4 in 2.00 L of solution b. 3.00 mol of KI in 2.39 L of solution c. 0.206 mol of HF in 752 mL of solution. (HF is used for etching glass.) Chapter 6

  20. Exercise 6.20 How many grams of potassium hydroxide is required to prepare each of the following solutions? Example 6.20  How many grams of NaCl is required to prepare 0.500 L of typical over-the-counter saline solution (about 0.15 M NaCl)? a. 2.00 L of 6.00 M KOH b. 100.0 mL of 1.00 M KOH Chapter 6

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