Why Intermolecular Forces Finally Make Sense When Students Can See the Attractions
- Androy Bruney
- Jan 16
- 5 min read
Updated: Jan 23
Why Intermolecular Forces Often Feel Like a Sudden Jump
This post is part of an ongoing series on teaching chemical bonding as a connected system. Links will be added as each post is published.
How to Teach Covalent Bonding in a Way Students Actually Understand(Building electron-sharing intuition before rules)
How I Get Students to Actually Master Lewis Dot Structures(Scaffolding + real-world context, without guesswork)
Why Molecular Geometry Finally Clicks When Students Can See VSEPR(Moving from Lewis structures to 3D reasoning)
How to Teach Molecular Polarity Without the Guesswork(Bond polarity → shape → symmetry → reasoning)
Why Intermolecular Forces Make Sense When Students Compare(Turning IMF into the payoff, not another memorization task)
Intermolecular forces tend to arrive in the curriculum like an unexpected detour — and students feel that shift immediately.
Up to this point, everything has been happening inside molecules. Students have been thinking about shared electrons, drawing structures, wrestling with shape, and finally making sense of polarity. Then, almost overnight, we ask them to switch perspectives and start talking about attractions between molecules instead.
After many years of teaching this unit, I don’t think students struggle with intermolecular forces because the ideas are too abstract. They struggle because the reasoning chain quietly breaks right when it matters most.
When IMF is introduced as a list of definitions — hydrogen bonding, dipole–dipole, London dispersion — students usually comply. They memorize the names. They can match terms on a quiz. But when you ask them to explain why one force dominates in a particular substance, the confidence disappears.
That’s not a motivation issue. It’s a sequencing issue.
Intermolecular Forces Are the Payoff of Everything That Came Before
By the time we reach intermolecular forces, students actually already have the tools they need.
From earlier in the unit, they understand:
how electrons are shared in covalent bonds,
how Lewis structures show where electrons are located,
how VSEPR explains molecular shape,
and how polarity creates uneven charge distribution.
Intermolecular forces aren’t a new idea layered on top of those concepts. They are the consequences of them.
When students recognize that IMF explains what their molecules do, not just what they’re called, the topic stops feeling like another hurdle and starts to feel like closure.
The Problem With Teaching IMF as Definitions First
When intermolecular forces are taught as isolated categories, students naturally fall back on shortcuts.
I hear comments like:
“It has an O–H bond, so it’s hydrogen bonding.”
“This one’s nonpolar, so it must be London dispersion.”
What’s missing isn’t effort — it’s comparison.
Students need to see multiple molecules side by side and decide which attractions matter most and why. Without that contrast, IMF turns into another labeling exercise instead of a reasoning task.
Why Visual Sorting Changes How Students Think About IMF
This is where an intermolecular forces card sort becomes genuinely instructional — not just engaging.
Instead of answering questions in isolation, students physically compare molecules. They place cards next to each other, debate dominant forces, and justify decisions out loud. In the process, misconceptions surface naturally — especially when two molecules share features but behave differently.
This approach aligns well with what we know about learning:
visual representations support deeper understanding,
Comparing examples strengthens pattern recognition,
and reducing cognitive load allows students to focus on reasoning instead of recall.
But more importantly, it mirrors how students actually think when they’re allowed to slow down and talk through ideas.
What the IMF Card Sort Looks Like in a Real Classroom
I usually run this activity in pairs or small groups. Each group gets a set of molecule cards and a simple prompt: sort these based on the dominant intermolecular force.
From there, my role shifts. I don’t jump in to correct immediately. I listen.
Students argue (politely), revise their thinking, and test ideas against evidence. When two molecules have similar molar masses or competing forces, the discussion gets especially rich — and those moments are far more valuable than any rule I could write on the board.
Because students handle one molecule at a time, the task feels manageable — even for students who typically struggle. No one is staring down a page full of questions, wondering where to start.
Why Card Sorts Reduce Overwhelm Better Than Worksheets
By the time we reach intermolecular forces, students are usually carrying a lot of cognitive baggage.
They’ve just worked through bonding, structure, shape, and polarity — and for many of them, those ideas are still settling. Handing out a full worksheet at this point, especially one packed with definitions and ranking questions, can feel like asking them to sprint when they’re still catching their breath.
I’ve learned this the hard way.
When students see a page filled with ten or twelve IMF questions, a good number of them shut down before they even start. Not because they can’t do the chemistry, but because the task looks overwhelming.
That’s where card sorts quietly do a lot of heavy lifting.
Cognitive Demand is Lower
With a card sort, the cognitive demand is spread out: one molecule at a time, one comparison at a time , one justification at a time.
Students aren’t trying to hold everything in their heads all at once. They’re making small, manageable decisions — and talking through them. That structure keeps the chemistry rigorous without making it feel inaccessible.
What I’ve noticed over the years is that once students have sorted, debated, and defended their choices, traditional practice suddenly becomes more productive.
When we return to questions about boiling point or dominant intermolecular forces, students aren’t guessing. They’re pulling from reasoning they’ve already rehearsed out loud.
Using Post-Sort Reflection to See What Students Really Understand
After the sort, I always ask for a short written reflection — nothing long or formal.
Questions like:
Which intermolecular force is strongest in this substance, and why?
What evidence supports your conclusion?
These quick responses tell me far more than a multiple-choice question ever could.
You can immediately see who understands the hierarchy of intermolecular forces — and who is still relying on surface-level cues like “this one has hydrogen” or “this molecule is bigger.”
Just as importantly, students start to realize that IMF decisions aren’t about memorizing labels. They’re about weighing evidence.
When Intermolecular Forces Stop Feeling Theoretical
This is the point in the unit where something really important happens.
Intermolecular forces stop feeling like abstract forces floating between molecules — and start explaining things students recognize.
They can now articulate why:
water has an unusually high boiling point,
ethanol and acetone behave differently despite similar sizes,
larger nonpolar molecules often boil at higher temperatures than smaller ones.
Those explanations don’t come from memorized charts.They come from comparison — from seeing patterns across molecules and defending conclusions.
That shift is subtle, but it’s powerful.
Final Thoughts
Intermolecular forces work best when they’re taught as the logical conclusion of bonding, structure, and polarity — not as a stand-alone list of terms tacked on at the end of the unit.
When students can see and compare molecular attractions, the topic becomes coherent instead of overwhelming.
And in my experience, that’s when students stop asking, “What category is this?”and start asking, “What’s really happening here?”
A Note for Teachers Looking for Structure Without Rigidity
If you’re looking for a way to teach intermolecular forces that builds on everything students already know — without adding more memorization — the Intermolecular Forces Card Sort is designed to support exactly this kind of reasoning.
It gives students space to compare, discuss, and justify before moving into traditional practice — and it fits naturally at the end of a well-sequenced bonding unit.
