Phase Changes and Intermolecular Forces Chapter 13.1-13.3

1. Properties of solids, liquids, and gases Solids: densely packed and organized Gases: widely spaced and disorganized Liquids: in between, disorganized, but still fairly dense.

2. What states of water can coexist at 0 C 2. What states of water can coexist at 0 C? What are these temperatures known as? 0 C Solid/Liquid Melting/Freezing 100 C Liquid/Gas Boiling

3. Draw the Heating Curve of Water

3. the Heating Curve of Other Substances Iron  Nitrogen: Melting/Freezing Point: -210 C Boiling Point: -195 C

4. Does the figure look like sections from the Water and Methanol lab?

5. Does it take more heat to increase the temperature of water from 0C to 100C or to evaporate it completely? It takes more energy to go though a phase change than it does to change the temperature. Look a the amount of time/energy it took to change the liquid to a gas (which is boiling).

6. What is the difference between intermolecular forces and Intramolecular forces? Intermolecular = between multiple molecules/atoms Examples: London Dispersion, Hydrogen bonds, Ionic Bonding, dipole-dipole forces Intramolecular = Within a molecule Example: Covalent, Polar covalent, and Ionic Bonding

7. Define Heat of fusion and Heat of Vaporization. Heat of Fusion: The amount of energy it takes to turn a substance from a solid to a liquid. (Takes place at MP) Heat of Vaporization: The amount of energy it take to turn a substance from a liquid to a gas. (Takes place at BP)

7. Which is usually a higher amount of energy 7. Which is usually a higher amount of energy? Does this make sense given the properties of S, L, and G? The heat of vaporization is much higher that the heat of fusion. IMFA = Intermolecular Forces of Attraction In solids the IMFA are holding the molecules in a neat organized crystal lattice. When it melts (Heat of fusion) the IMFA still hold the molecules together, but they are disorganized. When a substance is boiled (heat of vaporization) the IMFA are broken and the molecules bounce around the container. It takes more energy to break the IMFA than it does to disorganize it.

8. Rank the IMFA in order of increasing strength: London Dispersion forces Dipole-Dipole forces Hydrogen Bonds Ionic Bonding

Draw flow chart while we discuss the different types

8. Rank the IMFA in order of increasing strength: 1. London Dispersion forces Type of Intramolecular force: Covalent Bonding or Non-Bonded Noble Gas Polarity: Non-polar Cause of IMFA: Electrons are not always equally spaced around a non-polar molecule. Causes temporary dipoles.

8. Rank the IMFA in order of increasing strength: 1. Dipole-Dipole forces Type of Intramolecular force: Polar Covalent Bonding Polarity: Polar (but not Hydrogen bonds) Cause of IMFA: The dipole moments in polar molecules cause the molecule to have positive and negative ends. The positive end of molecules attract the negative ends of other molecules.

8. Rank the IMFA in order of increasing strength: 3. Hydrogen Bonds Type of Intramolecular force: Polar Covalent Bonding (But only when H is bonded to O, F, and N) Polarity: More polar than dipole-dipole forces Cause of IMFA: Similar to dipole-dipole, but hydrogen bonds are more polar, so there is a greater attraction between molecules

8. Rank the IMFA in order of increasing strength: 4. Ionic Bonding Type of Intramolecular force: Ionic Bonding Polarity: Very Polar, full charges Cause of IMFA: The positive cations are strongly attracted to the negative anions that surround it (and vice- versa).

9. Which elements does hydrogen need to be bonded with in order to have hydrogen bonding?

10. Which IMFA does each molecule use? Molecules Type of IMFA Phase at Room Temp HBr   Gas BP= -66 NF3 Gas BP= -129 Kr Gas BP= -153 N2 Gas BP= -195 H2S Gas BP= -60 NaCl Solid BP= 1413 H2O Liquid BP= 100

11. Rank the IMFA in increasing BP London Dispersion forces Dipole-Dipole forces Hydrogen Bonds Ionic Bonding

10. Which IMFA does each molecule use? Molecules Type of IMFA Phase at Room Temp HBr  Dipole-Dipole Gas BP= -66 NF3 Gas BP= -129 Kr  London Dispersion Gas BP= -153 N2 Gas BP= -195 H2S  Hydrogen Gas BP= -60 NaCl  Ionic Solid BP= 1413 H2O Hydrogen Liquid BP= 100

12. Which atoms/molecules have the greatest London Dispersion forces? The larger the size of the atoms the bigger the instantaneous dipole and the stronger the force. The Higher the BP

Which would have a higher BP? (remember BP is correlated to polarity) Kr or Xe N2 or O2 NF3 or NH3 CH4 or CH3OH NH3 or H2O