Liquids, Solids, and 12
Intermolecular Forces
Chapter Overview
The molecular-level interactions of solids and liquids are discussed. Phase changes are
Lecture Outline
12.1 Interactions Between Molecules
12.2 Properties of Liquids and Solids
Learning Objective: Describe the properties of solids and liquids and relate them to their
constituent atoms and molecules.
A. Properties of liquids
2. Indefinite shape, fluid
3. Definite volume
B. Properties of solids
1. High densities compared to gases
3. Definite volume
12.3 Intermolecular Forces in Action: Surface Tension and Viscosity
Learning Objective: Describe how surface tension and viscosity are manifestations of the
intermolecular forces in liquids.
12.4 Evaporation and Condensation
Learning Objective: Describe and explain the processes of evaporation and condensation.
A. Evaporation and vaporization – liquid to gas
12.5 Melting, Freezing, and Sublimation
Learning Objective: Use the heat of fusion in calculations.
A. Melting – solid to liquid
12.6 Types of Intermolecular Forces: Dispersion, Dipole–Dipole, Hydrogen Bonding, and
Ion–Dipole
Learning Objective: Compare and contrast four types of intermolecular forces:
A. Dispersion force, also known as London force
1. Weakest intermolecular force
3. Involved in every intermolecular interaction
B. Dipole-dipole force
2. Strength is a function of dipole moment and structure
C. Hydrogen bonding
2. Only involving F, O, or N bonded to a hydrogen atom
D. Ion-dipole force
2. Important in aqueous solutions of ionic compounds
12.7 Types of Crystalline Solids: Molecular, Ionic, and Atomic
Learning Objective: Identify types of crystalline solids.
A. Molecular solids
2. Examples, dry ice(CO2(s)), ice (H2O(s))
B. Ionic solids
2. Examples, NaCl, CaF2
C. Atomic solids
2. Covalent atomic solids
4. Metallic atomic solids
12.8 Water: A Remarkable Molecule
Learning Objective: Describe and explain the properties that make water unique among
molecules.
Chemical Principle Teaching Ideas
Properties of Liquids
Look at a sample of liquid that students see every day, such as a bottle of soda. Ask the
students about the liquid and measurable properties. Can it be compressed? What shape does it
take? This real world example will help them understand the properties and will also help them
remember the ideas presented.
Properties of Solids
Manifestations of Intermolecular Forces
Again, real-world examples are a good tool for these concepts. Showing a sample of thick
oil slowly pouring out of a container will show them viscosity. Pointing out that some animals
depend on surface tension for their very existence (water bugs) will show them how important
the concept is for biological species.
Evaporation and Condensation
Talk about what affects the rate of evaporation. What happens when you heat the liquid?
The molecules are moving faster, so more of them have enough energy to leave the liquid state.
Melting and Freezing
Do a sample calculation of how much energy is required to melt 1 L of solid water.
Types of Intermolecular Forces
To help show the relative magnitude of each kind of intermolecular force, give the
measured dipole moments of a variety of species. Students frequently forget that dispersion
Types of Crystalline Solids
Giving several real-world examples of each kind of bonding type will help the students
remember their respective properties. Make sure to point out the fundamental measurable
Water
Remind the students that their very existence depends on this strange behavior of water.
Explain what would happen to lakes in the cold winter if solid water (ice) sank instead of floated.
Skill Builder Solutions
12.1. Hvap is a conversion factor between amount of a substance and energy.
Heat required = mass × Hvap =
Plus. First, calculate the amount of heat released from the condensation. Then calculate the
change in temperature of the aluminum metal.
12.2.
2
15.5 g H O 2
2
1 mol H O
18.02 g H O
2
= 0.861 mol H O
Plus. Heat from melting of ice = Hfusion x molH2O
12.3. Methane has a molecular weight of 16.04, and C2H6 has a weight of 30.07 g/mol. Since
12.4. a. CI4 is tetrahedral in geometry, and the C and all the I have identical electronegativities
so the individual bonds are nonpolar, so there are no intermolecular dipole-dipole
interactions.
12.5. Both species have strong dipole-dipole intermolecular forces; however, HF has
12.6. a. Ammonia (NH3) is a polar covalent molecule; thus it is a molecular solid.
Suggested Demonstrations
Measure the mass of a piece of ice and place it in a beaker on an activated hot plate. Have the
students calculate how much energy will be required to change the ice into water gas.
Guided Inquiry Ideas
Below are a few example questions that students answer in the guided inquiry activities provided
in the Guided Activity Workbook.
Define intermolecular force using a complete sentence.