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Unit 13 Liquids and Solids
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Unit 13 Liquids and Solids

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  1. Unit 13 Liquids and Solids Book Chapter 14

  2. Ice, the solid form of water, providesrecreation for this ice climber.

  3. Wind surfers use liquid water for recreation.

  4. Did you know? • Water density as gas is 2000x less than water liquid. • Water and ice have very similar densities • Takes almost 7x more energy to convert liquid water to water vapor as it does to convert ice to liquid

  5. Water and ice are more alike than steam. • Why?

  6. Water and its Phase changes 1. How much of the earth’s surface is covered with water? • 70% 2. Why is water so important? • We are made up of 60% water • Oceans help moderate earth’s temp • Cools auto engines and nuclear reactors • Provides means of transportation

  7. 3. What happens when you heat ice? • Molecules gain enough energy to break the weak bonds that hold them rigidly together and start sliding past each other 4. What do we call the temp at 1 atm of pressure when solid turns to liquid? • Melting point

  8. 5. What do we call the temp at 1 atm when liquid turns into gas? • Boiling point 6. What do we call a graph that illustrates these temperature changes • Heating curve

  9. 7. Why does temp stop when solids melt? • All the energy is flowing from the warmer molecules to melt the cooler ones(average is kept at mp)

  10. 8. Why does temp stop when a liquid boils? • The energy that could have continued the heating is being taken away by the molecules that are vaporizing 9. What is the most interesting feature of water? • D of liquid is 1.00 g/mL, solid 0.917 g/mL

  11. 10. Why is the water/ice density difference so important?

  12. Energy Requirements for Changes of State 11. Are phase changes chemical or physical changes? • Physical 12. What is actually being separated during a phase change • The weak bonds holding molecules together

  13. 13. If a phase change was chemical, what would be breaking? • The strong bonds that hold the atoms together within the molecule 14. What do we call the forces that hold atoms together? • Intramolecular bonds

  14. 15. What are examples of these bonds? • Ionic, covalent, metallic 16. What do we call the bonds that hold molecules together? • Intermolecular bonds

  15. 17. What kind of motion can intermolecular forces exhibit? • Vibrational

  16. 18. What happens when you heat up a substance? • Vibrational motion increases • Going from S--> L, the motion allows the molecules to move around more freely • In boiling, the forces are snapped and the molecules will move away from each other

  17. 19. What is the heat of fusion? • Amount of heat energy needed to melt one mole of a solid substance 20. What is the heat of fusion for water? • 6.02 kJ/mol

  18. 21. What is the heat of vaporization? • Amount of heat energy to boil one mole of a liquid substance 22. What is the heat of vaporization for water? • 40.6 kJ/mol

  19. 23. Why is the heat of vaporization for water 7x greater than the heat of fusion for water? • Because you have to break the intermolecular bonds instead of just loosen them as in melting

  20. Ex. 1 Calculate the energy required to melt 8.5 g of ice at 0C. The molar heat of fusion for ice is 6.02 kJ/mol. Ex. 2 Calculate the energy(in KJ) required to heat 25 g of water from 25 C to 100 C. The specific heat of water is 4.18 J/gC and the molar heat of vaporization is 40.6 kJ/mol.

  21. Read Chem in Focus p. 431 for quiz tomorrow

  22. Intermolecular Forces 24. What is a dipole moment again? 25. What happens when dipoles come in contact with each other? • They orient themselves + side of one molecule to - side of the other 26. What do we call the bonds that cause these molecules to stick together? • Dipole-Dipole bonds

  23. 27. How do dipole-dipole bonds compare with a covalent or ionic bond? • 1% as strong and becomes weaker as the molecules get farther away 28. What is the strongest type of dipole-dipole bond? • Hydrogen bonding

  24. 29. Why is the Hydrogen bond so strong? • It occurs between H and N, O, or F • Those atoms are so electronegative that H will have very little control of its own e- • This bond will be very close to being an ionic bond

  25. 30. Why is H bonding so important for life? • Bodies of water freeze top down • Surface tension and plants • DNA, RNA, Proteins held together by H bonding

  26. 31. How do we know that non polar molecules must have some kind of intermolecular attraction? • They can form liquids and solids, can’t they? 32. What do we call the forces that hold non polar molecules together? • London dispersion forces

  27. 33. How are LDF formed?

  28. 34.. What can make LDF stronger? • The number of e- involved, more e-(the larger the molecule) the stronger the LDF 35. What is an example of substances held together by strong LDF? • plastics

  29. Evaporation 36. What do we call the process by which a liquid becomes gas BELOW bp? • Evaporation

  30. 37. What happens when a liquid molecule evaporates? • Individual molecules gain enough KE to break the H bonds at the surface and become gas 38. Why is evaporation the key to life on earth? • A lot of the energy from the sun is used to cause evaporation, it regulates the heat.

  31. 39. How does evaporation preserves human life? • We use it to cool off--perspiration

  32. Vapor Pressure 40. You have a clear container, 1/3 full of water, you seal it up, what will happen the volume of the water after one day? • Decrease 41. What will happen after two days? • Decrease

  33. 42. What will happen after three days? • Remains the same 43. Why has the volume of the water stopped decreasing? • The number of molecules evaporating equals the number of molecules condensing

  34. 44. What is condensation? • When molecules lose enough energy to reform the intermolecular bonds and become liquids 45. What do we call this system? • Vapor Liquid Equilibrium or Dynamic Equilibrium

  35. 46. What is a barometer? • A device that measures gas pressure 47. What is gas pressure? • The push that gas molecules apply when they bounce against the walls of a container

  36. 48. What would have happened if you had placed a tiny barometer in the beaker mentioned before? • The barometer would have registered a steady pressure increase 49. What would be causing the pressure increase? • The increased numbers of evaporated water

  37. 50. What do we call the pressure caused by the evaporated molecules? • Vapor pressure 51. What was the barometer like? Who invented it? • 3 stories tall, used water, Evangelista Torricelli