Lecture 15.1 & 15.2- Water

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Section 15.1 & 15.2 Lecture for Honors & Prep Chemistry

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  • In a water molecule, the bond polarities are equal, but the two dipoles do not cancel each other because a water molecule is bent. The molecule as a whole is polar. Applying Concepts Which element in water has the higher electronegativity?
  • The polarity of the water molecule results in hydrogen bonding. a) Partial negative charges are on each oxygen atom; partial positive charges are on the hydrogen atom. b) Because of polarity, hydrogen bonds form. Inferring To form a hydrogen bond, what must be true about the hydrogen and the element to which it is hydrogen bonded?
  • The polarity of the water molecule results in hydrogen bonding. a) Partial negative charges are on each oxygen atom; partial positive charges are on the hydrogen atom. b) Because of polarity, hydrogen bonds form. Inferring To form a hydrogen bond, what must be true about the hydrogen and the element to which it is hydrogen bonded?
  • Extensive hydrogen bonding in ice holds the water molecules farther apart in a more ordered arrangement than in liquid water. The hexagonal symmetry of a snowflake reflects the structure of the ice crystal.
  • A solution cannot be separated by filtration. The small size of the solute particles allows them to pass through filter paper.
  • When an ionic solid dissolves, the ions become solvated or surrounded by solvent molecules. Inferring Why do the water molecules orient themselves differently around the anions and the cations?
  • Oil and water do not mix. Oil is less dense than water, so it floats on top. The colors result from the bending of light rays by the thin film of oil.
  • A solution conducts electricity if it contains ions. a) Sodium chloride, a strong electrolyte, is nearly 100% dissociated into ions in water. b) Mercury(II) chloride, a weak electrolyte, is only partially dissociated in water. c) Glucose, a nonelectrolyte, does not dissociate in water.
  • A solution conducts electricity if it contains ions. a) Sodium chloride, a strong electrolyte, is nearly 100% dissociated into ions in water. b) Mercury(II) chloride, a weak electrolyte, is only partially dissociated in water. c) Glucose, a nonelectrolyte, does not dissociate in water.
  • A solution conducts electricity if it contains ions. a) Sodium chloride, a strong electrolyte, is nearly 100% dissociated into ions in water. b) Mercury(II) chloride, a weak electrolyte, is only partially dissociated in water. c) Glucose, a nonelectrolyte, does not dissociate in water.
  • Water can be driven from a hydrate by heating. a) Heating of a sample of blue CuSO 4 ·5H 2 O begins. b) After a time, much of the blue hydrate has been converted to white anhydrous CuSO 4 .
  • Water can be driven from a hydrate by heating. a) Heating of a sample of blue CuSO 4 ·5H 2 O begins. b) After a time, much of the blue hydrate has been converted to white anhydrous CuSO 4 .
  • Deliquescent substances can remove water from the air. a) Sodium hydroxide pellets absorb moisture from the air. b) Eventually a solution is formed. Applying Concepts Identify the solvent and the solute.
  • Deliquescent substances can remove water from the air. a) Sodium hydroxide pellets absorb moisture from the air. b) Eventually a solution is formed. Applying Concepts Identify the solvent and the solute.
  • Lecture 15.1 & 15.2- Water

    1. 1. <ul><ul><ul><li>A water molecule is polar. </li></ul></ul></ul>15.1
    2. 2. <ul><ul><ul><li>Polar molecules are attracted to one another by dipole interactions. The negative end of one molecule attracts the positive end of another molecule. </li></ul></ul></ul>15.1
    3. 3. <ul><ul><ul><li>The intermolecular attraction among water molecules is called hydrogen bonding. </li></ul></ul></ul>15.1
    4. 4. <ul><ul><li>See how hydrogen bonding results in the unique properties of water. </li></ul></ul>
    5. 5. <ul><ul><li>Many unique and important properties of water—including its high surface tension and low vapor pressure—result from hydrogen bonding. </li></ul></ul>15.1
    6. 6. <ul><ul><li>The inward force, or pull, that tends to minimize the surface area of a liquid is called surface tension . </li></ul></ul><ul><ul><ul><ul><li>Water’s surface tension is higher than most. </li></ul></ul></ul></ul>15.1
    7. 7. SURFACE TENSION REVEALED !
    8. 8. <ul><ul><ul><li>A surfactant reduces water’s surface tension by interfering with hydrogen bonds. </li></ul></ul></ul>15.1
    9. 9. <ul><ul><li>Vapor Pressure </li></ul></ul><ul><ul><ul><li>Hydrogen bonding explains water’s unusually low vapor pressure. </li></ul></ul></ul><ul><ul><ul><li>Hydrogen bonds hold water molecules together, so escape requires more energy and evaporation is slow. </li></ul></ul></ul>15.1
    10. 10. <ul><ul><ul><li>As water begins to cool, it behaves initially like a typical liquid. </li></ul></ul></ul><ul><ul><ul><li>Its molecules get closer together and its density gradually increases. </li></ul></ul></ul><ul><ul><ul><li>When the temperature of the water falls below 4˚C, the density of water starts to decrease. </li></ul></ul></ul>15.1
    11. 11. 15.1
    12. 12. <ul><ul><ul><li>Hydrogen bonds hold the water molecules in place in the solid phase. </li></ul></ul></ul>15.1
    13. 13. <ul><ul><ul><ul><li>The structure of ice is a regular open framework of water molecules arranged like a honeycomb. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>When ice melts, the “honeycomb” framework collapses, and the water molecules pack closer together, making liquid water more dense than ice. </li></ul></ul></ul></ul>15.1
    14. 14. <ul><li>Bellwork </li></ul><ul><li>Draw a picture of one water molecule. Label the molecule’s polarity. </li></ul><ul><li>What is the shape of the water molecule? </li></ul><ul><li>Which atom is the most electronegative? </li></ul><ul><li>Which atom has (atoms have) the partial negative charge? </li></ul>
    15. 15. Homogeneous Aqueous Systems <ul><li>An ordinary dill pickle from the deli can be a source of light! Iron or copper electrodes are inserted into the ends of the pickle and connected to a source of alternating electric current. You will learn what kind of solution conducts electricity. </li></ul>15.2
    16. 16. Solvents and Solutes <ul><ul><ul><ul><li>An aqueous solution is water that contains dissolved substances. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>In a solution, the dissolving medium is the solvent . </li></ul></ul></ul></ul><ul><ul><ul><ul><li>In a solution, the dissolved particles are the solute . </li></ul></ul></ul></ul>15.2
    17. 17.   Simple solutions are homogeneous mixtures of two substances.
    18. 18. A solute is the dissolved substance in a solution. A solvent is the major component in the solution. The solvent is often water
    19. 19. Solvents and Solutes <ul><ul><li>A solvent dissolves the solute. </li></ul></ul><ul><ul><li>The solute becomes dispersed in the solvent. </li></ul></ul><ul><ul><ul><li>Solvents and solutes may be gases, liquids, or solids. </li></ul></ul></ul><ul><ul><ul><li>Solute particles can be atoms, ions, or molecules. </li></ul></ul></ul>15.2
    20. 20. Aqueous = a solute dissolved in water NaCl(s)  Na + (aq) + Cl - (aq) shows that the ions are dissolved in water This equation for the dissolving of table salt reads… solid sodium chloride yields aqueous sodium ions and aqueous chloride ions.
    21. 21. Solvents and Solutes <ul><ul><ul><li>If you filter a solution through filter paper, both the solute and the solvent pass through the filter. </li></ul></ul></ul>15.2
    22. 22.        S olute and solvent particles are in constant random motion, which causes diffusion of the solute into the solvent, resulting in a homogeneous solution.
    23. 23.    When a solid is in contact with a liquid, at least some small degree of dissolution occurs. Dissolution= dissolving into solution molecules or ions in a solid leave their place in the solid to become surrounded by the solvent
    24. 24. The Solution Process <ul><ul><ul><li>When the positive and negative ions of a salt become surrounded by solvent molecules it is called solvation . Or dissolution. Or dissolving! </li></ul></ul></ul>
    25. 25. Dissociate = to come apart Dissociation describes the breaking up of an ionic solid.
    26. 26. Dissolving salt REVEALED !
    27. 27. The Solution Process <ul><ul><ul><li>LIKE DISSOLVES LIKE </li></ul></ul></ul><ul><ul><ul><ul><li>Polar solvents such as water dissolve ionic compounds and polar compounds. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Nonpolar solvents such as gasoline dissolve nonpolar compounds. </li></ul></ul></ul></ul>
    28. 28. The Solution Process <ul><ul><ul><li>Oil and water do not mix. </li></ul></ul></ul>
    29. 29. Electrolytes and Nonelectrolytes <ul><ul><ul><li>An electrolyte is a compound that conducts an electric current when it is in an aqueous solution or in the molten state. </li></ul></ul></ul><ul><ul><ul><ul><li>All ionic compounds are electrolytes because they dissociate into ions. </li></ul></ul></ul></ul>15.2
    30. 30. Electrolytes and Nonelectrolytes <ul><ul><ul><li>The bright glow shows that sodium chloride is a strong electrolyte because nearly all the dissolved sodium chloride exists as separate Na + and Cl – ions. </li></ul></ul></ul>15.2
    31. 31. Electrolytes and Nonelectrolytes <ul><ul><ul><li>A weak electrolyte conducts electricity poorly because only a fraction of the solute in the solution exists as ions. </li></ul></ul></ul>
    32. 32. Electrolytes and Nonelectrolytes <ul><ul><ul><li>A compound that does not conduct an electric current in either aqueous solution or the molten state is called a nonelectrolyte . </li></ul></ul></ul>
    33. 33. <ul><ul><ul><li>A compound that contains water of hydration is called a hydrate . </li></ul></ul></ul><ul><ul><ul><ul><li>In writing the formula of a hydrate, use a dot to connect the formula of the compound and the number of water molecules per formula unit. </li></ul></ul></ul></ul>Hydrates 15.2
    34. 34. Hydrates <ul><ul><ul><li>A sample of blue CuSO 4 ·5H 2 O is heated. </li></ul></ul></ul>15.2
    35. 35. Hydrates <ul><ul><ul><li>Blue crystals of CuSO 4 ·5H 2 O crumble to a white anhydrous powder that has the formula CuSO 4 . </li></ul></ul></ul>
    36. 36. Hydrates 15.2
    37. 37. Hydrates <ul><ul><li>Efflorescent Hydrates </li></ul></ul><ul><ul><ul><li>If a hydrate has a vapor pressure higher than the pressure of water vapor in the air, the hydrate will lose its water of hydration, or effloresce. </li></ul></ul></ul>15.2
    38. 38. Hydrates <ul><ul><li>Hygroscopic Hydrates </li></ul></ul><ul><ul><ul><li>Hydrated salts that have a low vapor pressure remove water from moist air to form higher hydrates. These hydrates and other compounds that remove moisture from air are called hygroscopic. </li></ul></ul></ul>15.2
    39. 39. Practice Problem For Sample Problem 15.1 for Sample Problem 15.1
    40. 40. Hydrates <ul><ul><li>Deliquescent Compounds </li></ul></ul><ul><ul><ul><li>Deliquescent compounds remove sufficient water from the air to dissolve completely and form solutions. These compounds become wet when exposed to normally moist air. </li></ul></ul></ul>
    41. 41. Hydrates <ul><ul><ul><li>The deliquescent substance, sodium hydroxide, absorbs moisture from air. </li></ul></ul></ul>
    42. 42. Hydrates <ul><ul><ul><li>A solution forms. </li></ul></ul></ul>
    43. 43. <ul><ul><li>1. Many of the unusual properties of water are the result of </li></ul></ul><ul><ul><ul><li>hydrogen bonding. </li></ul></ul></ul><ul><ul><ul><li>nonpolar molecules. </li></ul></ul></ul><ul><ul><ul><li>low molar mass. </li></ul></ul></ul><ul><ul><ul><li>dispersion forces. </li></ul></ul></ul>15.1 Section Quiz.
    44. 44. <ul><ul><li>1. Many of the unusual properties of water are the result of </li></ul></ul><ul><ul><ul><li>hydrogen bonding. </li></ul></ul></ul><ul><ul><ul><li>nonpolar molecules. </li></ul></ul></ul><ul><ul><ul><li>low molar mass. </li></ul></ul></ul><ul><ul><ul><li>dispersion forces. </li></ul></ul></ul>15.1 Section Quiz.
    45. 45. <ul><ul><li>2. A surfactant causes water to spread out over a surface. This spreading occurs because the surfactant </li></ul></ul><ul><ul><ul><li>attaches to the surface. </li></ul></ul></ul><ul><ul><ul><li>interferes with hydrogen bonding. </li></ul></ul></ul><ul><ul><ul><li>lowers the vapor pressure. </li></ul></ul></ul><ul><ul><ul><li>lowers the density of water. </li></ul></ul></ul>15.1 Section Quiz.
    46. 46. <ul><ul><li>2. A surfactant causes water to spread out over a surface. This spreading occurs because the surfactant </li></ul></ul><ul><ul><ul><li>attaches to the surface. </li></ul></ul></ul><ul><ul><ul><li>interferes with hydrogen bonding. </li></ul></ul></ul><ul><ul><ul><li>lowers the vapor pressure. </li></ul></ul></ul><ul><ul><ul><li>lowers the density of water. </li></ul></ul></ul>15.1 Section Quiz.
    47. 47. <ul><ul><li>3. Ice is less dense than liquid water because in ice the water molecules </li></ul></ul><ul><ul><ul><li>expand because of weakened covalent bonds. </li></ul></ul></ul><ul><ul><ul><li>have a regular open honeycomb framework. </li></ul></ul></ul><ul><ul><ul><li>expand because of weakened hydrogen bonds. </li></ul></ul></ul><ul><ul><ul><li>have a more disorderly arrangement with lower density. </li></ul></ul></ul>15.1 Section Quiz.
    48. 48. <ul><ul><li>3. Ice is less dense than liquid water because in ice the water molecules </li></ul></ul><ul><ul><ul><li>expand because of weakened covalent bonds. </li></ul></ul></ul><ul><ul><ul><li>have a regular open honeycomb framework. </li></ul></ul></ul><ul><ul><ul><li>expand because of weakened hydrogen bonds. </li></ul></ul></ul><ul><ul><ul><li>have a more disorderly arrangement with lower density. </li></ul></ul></ul>15.1 Section Quiz.
    49. 49. <ul><ul><li>1. Choose the correct words for the spaces. In any solution, the material that is dissolved is called the _______ and the material in which the substance is dissolved is called the _______ . </li></ul></ul><ul><ul><ul><li>solid, liquid </li></ul></ul></ul><ul><ul><ul><li>solvent, solute </li></ul></ul></ul><ul><ul><ul><li>solute, solvent </li></ul></ul></ul><ul><ul><ul><li>crystal, disperser </li></ul></ul></ul>15.2 Section Quiz.
    50. 50. <ul><ul><li>1. Choose the correct words for the spaces. In any solution, the material that is dissolved is called the _______ and the material in which the substance is dissolved is called the _______ . </li></ul></ul><ul><ul><ul><li>solid, liquid </li></ul></ul></ul><ul><ul><ul><li>solvent, solute </li></ul></ul></ul><ul><ul><ul><li>solute, solvent </li></ul></ul></ul><ul><ul><ul><li>crystal, disperser </li></ul></ul></ul>15.2 Section Quiz.
    51. 51. <ul><ul><li>2. In the solution process, the </li></ul></ul><ul><ul><ul><li>solvent molecules are surrounded by positive and negative ions. </li></ul></ul></ul><ul><ul><ul><li>solvent molecules become dispersed in an ionic crystal. </li></ul></ul></ul><ul><ul><ul><li>ions become emulsified in the solvent. </li></ul></ul></ul><ul><ul><ul><li>positive and negative ions are surrounded by solvent molecules. </li></ul></ul></ul>15.2 Section Quiz.
    52. 52. <ul><ul><li>2. In the solution process, the </li></ul></ul><ul><ul><ul><li>solvent molecules are surrounded by positive and negative ions. </li></ul></ul></ul><ul><ul><ul><li>solvent molecules become dispersed in an ionic crystal. </li></ul></ul></ul><ul><ul><ul><li>ions become emulsified in the solvent. </li></ul></ul></ul><ul><ul><ul><li>positive and negative ions are surrounded by solvent molecules. </li></ul></ul></ul>15.2 Section Quiz.
    53. 53. <ul><ul><li>3. All ionic compounds are electrolytes because they </li></ul></ul><ul><ul><ul><li>conduct electricity in the solid state. </li></ul></ul></ul><ul><ul><ul><li>dissociate into ions in the aqueous and/or the molten state. </li></ul></ul></ul><ul><ul><ul><li>remain as positive-negative pairs even when dissolved. </li></ul></ul></ul><ul><ul><ul><li>only conduct electricity in the molten state. </li></ul></ul></ul>15.2 Section Quiz.
    54. 54. <ul><ul><li>3. All ionic compounds are electrolytes because they </li></ul></ul><ul><ul><ul><li>conduct electricity in the solid state. </li></ul></ul></ul><ul><ul><ul><li>dissociate into ions in the aqueous and/or the molten state. </li></ul></ul></ul><ul><ul><ul><li>remain as positive-negative pairs even when dissolved. </li></ul></ul></ul><ul><ul><ul><li>only conduct electricity in the molten state. </li></ul></ul></ul>15.2 Section Quiz.
    55. 55. <ul><ul><li>4. The formula for iron(II) sulfate heptahydrate is </li></ul></ul><ul><ul><ul><li>FeSO 4 (H 2 O) 7 </li></ul></ul></ul><ul><ul><ul><li>FeSO 4 •(H 2 O) 7 </li></ul></ul></ul><ul><ul><ul><li>Fe•2SO 4 •7H 2 O </li></ul></ul></ul><ul><ul><ul><li>FeSO 4 •7H 2 O </li></ul></ul></ul>15.2 Section Quiz.
    56. 56. <ul><ul><li>4. The formula for iron(II) sulfate heptahydrate is </li></ul></ul><ul><ul><ul><li>FeSO 4 (H 2 O) 7 </li></ul></ul></ul><ul><ul><ul><li>FeSO 4 •(H 2 O) 7 </li></ul></ul></ul><ul><ul><ul><li>Fe•2SO 4 •7H 2 O </li></ul></ul></ul><ul><ul><ul><li>FeSO 4 •7H 2 O </li></ul></ul></ul>15.2 Section Quiz.

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