Chemistry · 9th Grade

Active learning ideas

Intermolecular Forces (IMFs)

Active learning works well for intermolecular forces because students often confuse molecular-level interactions with chemical bonding. By manipulating physical models, discussing real data, and arguing from evidence, students build accurate mental models of forces that are invisible but govern observable properties like boiling point and solubility.

• Common Core State Standards
• HS-PS1-3
• STD.CCSS.ELA-LITERACY.RST.9-10.3

• 20–35 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: Boiling Point Predictions

Students receive six molecules with structures but no boiling points and predict the ranking. They compare with a partner and justify their reasoning before the actual data is revealed. Each discrepancy triggers a 'why were you wrong?' discussion that deepens understanding.

Differentiate between intramolecular bonds and intermolecular forces.

Facilitation Tip

During Think-Pair-Share: Boiling Point Predictions, circulate and listen for students using terms like 'temporary dipoles' or 'hydrogen bond donors' when justifying their rankings.

What to look for

Provide students with a list of simple molecules (e.g., CH4, H2O, HCl, NH3). Ask them to identify the dominant IMF for each and rank them from weakest to strongest IMF. Then, ask them to predict which molecule will have the highest boiling point and why.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 02

• Gallery Walk
• 35 min · Small Groups

Gallery Walk: IMF Evidence Hunt

Stations around the room present real-world phenomena: why detergents work, how geckos cling, why ice floats, why gasoline is less viscous than motor oil. Groups identify the dominant IMF at each station and defend their choice on sticky notes before a whole-class debrief.

Explain how the type and strength of IMFs influence a substance's physical properties (e.g., boiling point, viscosity).

Facilitation Tip

During Gallery Walk: IMF Evidence Hunt, place a timer at each station to keep groups moving efficiently while still allowing time for focused observation.

What to look for

Pose the question: 'Why does rubbing alcohol (isopropanol) evaporate much faster than cooking oil, even though both are liquids at room temperature?' Guide students to discuss the molecular structures, polarity, and resulting IMFs that explain the difference in evaporation rates.

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

Activity 03

• Inquiry Circle
• 25 min · Pairs

Whiteboard Modeling: Molecular Structures and IMFs

Student pairs draw two molecules on small whiteboards, label the dominant IMF between them, and justify their choice to another pair. The class compares all examples to build a collective ranking of IMF strength.

Predict the dominant intermolecular force present in a given molecular compound.

Facilitation Tip

During Whiteboard Modeling: Molecular Structures and IMFs, provide colored markers so students can clearly distinguish covalent bonds from IMFs in their diagrams.

What to look for

On an index card, have students draw a simple diagram showing the interaction between two molecules of water, labeling the hydrogen bonds. Then, ask them to write one sentence explaining why water has a higher boiling point than methane.

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Activity 04

• Inquiry Circle
• 30 min · Small Groups

Data Analysis: IMF vs. Physical Properties

Students analyze a dataset of ten compounds with known IMFs, boiling points, viscosities, and surface tensions. Groups draw conclusions about the relationship between IMF type and each property, then present one pattern they found to the class.

Differentiate between intramolecular bonds and intermolecular forces.

Facilitation Tip

During Data Analysis: IMF vs. Physical Properties, pre-print graphs on large paper so students can annotate directly with their reasoning about trends.

What to look for

Provide students with a list of simple molecules (e.g., CH4, H2O, HCl, NH3). Ask them to identify the dominant IMF for each and rank them from weakest to strongest IMF. Then, ask them to predict which molecule will have the highest boiling point and why.

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

A few notes on teaching this unit

Teachers should introduce IMFs with concrete, everyday examples first, like why ice floats or why water beads on wax paper. Avoid starting with abstract definitions; instead, let students discover the patterns through structured tasks. Research shows that students grasp the hierarchy of forces better when they first experience the extremes (strong hydrogen bonding in water versus weak London forces in methane) before tackling intermediate cases.

Successful learning looks like students correctly identifying the types of IMFs present in a molecule, explaining how IMF strength relates to physical properties, and using structural features to predict relative boiling points across different substances.

---

Watch Out for These Misconceptions

• During Think-Pair-Share: Boiling Point Predictions, watch for students labeling any molecule with hydrogen as having hydrogen bonding.

  Use the provided molecular sets to prompt students: 'Does this molecule have H bonded to N, O, or F? If not, it cannot form hydrogen bonds. Which IMF does it have instead?'

• During Data Analysis: IMF vs. Physical Properties, watch for students stating that breaking IMFs breaks the molecule apart.

  Refer students to the boiling point data: 'When water boils, we see steam rising. Is that water molecules or H and O atoms? What does this tell us about what is being broken?' Use the magnet analogy to model molecular separation.

• During Whiteboard Modeling: Molecular Structures and IMFs, watch for students ignoring London dispersion forces in polar molecules.

  Ask students to add 'London dispersion forces' to their whiteboard diagrams for every molecule, even polar ones, and explain why these forces are always present regardless of polarity.

---

Methods used in this brief

• Think-Pair-Share
• Gallery Walk
• Inquiry Circle