Summary

In this activity, students will apply their knowledge of molecular polarity, shape, and intermolecular forces to explain the differences in properties between different covalent substances.

Grade Level

High School

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

• HS-PS1-1: Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
• HS-PS2-6: Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.
• Scientific and Engineering Practices:
  • Developing and Using Models
  • Analyzing and Interpreting Data

AP Chemistry Curriculum Framework

This activity supports the following units, topics and learning objectives:

• Unit 2: Compound Structure and Properties
  • Topic 2.1: Types of Chemical Bonds
    • 2.1.A: Explain the relationship between the type of bonding and the properties of the elements participating in the bond.
  • Topic 2.5: Lewis Diagrams
    • 2.5.A: Represent a molecule with a Lewis diagram.
  • Topic 2.6: Resonance and Formal Charge
    • 2.6.A: Represent a molecule with a Lewis diagram that accounts for resonance between equivalent structures or that uses formal charge to select between nonequivalent structures.
  • Topic 2.7: VSEPR and Hybridization
    • 2.7.A: Based on the relationship between Lewis diagrams, VSEPR theory, bond orders, and bond polarities:
• Unit 3: Properties of Substances and Mixtures
  • Topic 3.1: Intermolecular and Interparticle Forces
    • 3.1.A: Explain the relationship between the chemical structures of molecules and the relative strength of their intermolecular forces when: a. The molecules are of the same chemical species. b. The molecules are of two different chemical species.
  • Topic 3.2: Properties of Solids
    • 3.2.A: Explain the relationship among the macroscopic properties of a substance, the particulate-level structure of the substance, and the interactions between these particles.
  • Topic 3.10: Solubility
    • 3.10.A: Explain the relationship between the solubility of ionic and molecular compounds in aqueous and nonaqueous solvents, and the intermolecular interactions between particles.

Objectives

By the end of this activity, students should be able to

• Describe and understand a compound’s:
  • Name and chemical formula.
  • Intermolecular forces based on their structure and polarity.
  • Physical properties (i.e. melting/boiling point, solubility, and vapor pressure).
• Draw a Lewis Structure including all bonding and nonbonding electrons
• Determine the VSEPR shape with corresponding bond angle(s). NOTE: Do not have students identify shape name and bond angle for organic molecules.
• Analyze the dipole moments to determine overall molecular polarity.
• Contrast and compart the properties of two similar compounds based on their shape, polarity, and intermolecular forces.

Chemistry Topics

This activity supports students’ understanding of

• Molecules and Bonding
• Covalent Bonding
• Lewis Structures
• VSEPR Shapes
• Electronegativity
• Polarity
• Valence Electrons

Time

Teacher Preparation: 10 - 15 minutes

Lesson: 45 minutes (one class period)

Materials

• Student activity sheet
• Optional: modeling kits

Safety

• No specific safety precautions need to be observed for this project.

Teacher Notes

• This activity can be used to reinforce student understanding of the relationship between molecular structure and properties, or may serve as a summative assessment on the topic.
• A brief description of each substance has been given on the student activity sheet. You may choose to remove the description and have students conduct an online search of the common properties and uses of each.
• If you have molecular modeling kits available, and the time to use them, have the students build models of each molecule before identifying the shape, polarity, and intermolecular forces of each. Students can also refer to the models when answering the questions asking them to compare and contrast the properties of similar molecules.
• An Answer Key document is available for teacher reference. All images of molecular models are open sourced images from Wikimedia

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