Chemistry · 12th Grade

Active learning ideas

Introduction to Solutions

Active learning works for solutions because students often confuse dissolving with disappearing or assume all mixtures behave the same way. Hands-on investigations let them observe particle-level behavior directly, turning abstract concepts like polarity and saturation into observable phenomena they can test and discuss.

• Common Core State Standards
• HS-PS1-3

• 15–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Stations Rotation
• 45 min · Small Groups

Predict and Test: Solubility Investigations

Students receive vials of water, ethanol, and hexane alongside six substances: NaCl, iodine crystals, sucrose, mineral oil, rubbing alcohol, and a vitamin C tablet. They predict which substance will dissolve in which solvent based on polarity analysis, run the tests, and reconcile any prediction errors by identifying which intermolecular force they misjudged.

Differentiate between solutions, suspensions, and colloids.

Facilitation Tip

During Predict and Test: Solubility Investigations, have students record exact volumes and masses before and after dissolving to emphasize precision in quantitative observations.

What to look for

Present students with three beakers containing water, oil, and salt. Ask them to predict which substance will dissolve in which, then test their predictions. Have them write a one-sentence explanation for each outcome using the 'like dissolves like' rule.

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Activity 02

• Stations Rotation
• 25 min · Small Groups

Card Sort: Solutions, Suspensions, and Colloids

Groups receive 12 scenario cards: orange juice, whole blood, fog, saltwater, Italian dressing, muddy water, milk, gelatin, soapy water, corn starch in water, air, and rubbing alcohol. They sort the cards into three categories and justify each placement by identifying particle size range and predicting how each would respond to the Tyndall test or settling over time.

Explain the 'like dissolves like' principle in terms of intermolecular forces.

Facilitation Tip

For Card Sort: Solutions, Suspensions, and Colloids, check that students use particle size and light-scattering evidence, not just appearance, to justify their choices.

What to look for

Provide students with a list of mixtures (e.g., saltwater, sand in water, milk, air). Ask them to classify each as a solution, suspension, or colloid and briefly justify their classification based on particle behavior.

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Activity 03

• Think-Pair-Share
• 15 min · Pairs

Think-Pair-Share: Rates of Dissolution

After a brief demo comparing a sugar cube, crushed sugar, and stirred crushed sugar dissolving in water at room and warm temperature, students individually rank the three dissolution-rate factors (stirring, temperature, particle size) from greatest to least effect. Pairs compare rankings and justify using particle-level reasoning, then share disagreements with the class.

Analyze the factors affecting the rate of dissolution.

Facilitation Tip

In Think-Pair-Share: Rates of Dissolution, ask students to predict how temperature and stirring affect dissolution rate before they test, then reconcile their predictions with observations.

What to look for

Pose the question: 'Imagine you are making iced tea. You add sugar to hot water and stir until it disappears, but then you add more sugar and it settles at the bottom. Explain this phenomenon using the terms solute, solvent, solubility, and saturation.'

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

Activity 04

• Gallery Walk
• 30 min · Small Groups

Gallery Walk: Polar vs. Nonpolar Molecular Models

Post diagrams or models of 8 to 10 common molecules: water, ethanol, glucose, hexane, CO2, acetone, cholesterol, and NaCl. Students circulate and annotate each with polar or nonpolar classification, the predicted best solvent, and the dominant intermolecular force responsible for solvation. Groups compare annotations and resolve disagreements before the whole-class debrief.

Differentiate between solutions, suspensions, and colloids.

Facilitation Tip

During Gallery Walk: Polar vs. Nonpolar Molecular Models, circulate to challenge groups to explain how hydrogen bonds or dipole interactions would form between their molecule and water.

What to look for

Present students with three beakers containing water, oil, and salt. Ask them to predict which substance will dissolve in which, then test their predictions. Have them write a one-sentence explanation for each outcome using the 'like dissolves like' rule.

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

A few notes on teaching this unit

Teachers should start with the simplest definition—what students can see—and build toward molecular explanations. Avoid front-loading theory; instead, let observations guide the discussion. Research shows that having students draw particle diagrams before and after dissolving helps bridge macroscopic observations to particulate-level reasoning. Always connect quantitative data (mass, volume) to qualitative explanations to reinforce that solutions are measurable systems.

By the end of these activities, students will confidently distinguish solutions from suspensions and colloids, explain solubility using intermolecular forces, and apply the 'like dissolves like' rule to real-world examples. Success looks like clear justifications, accurate classifications, and evidence-based predictions during discussions and experiments.

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Watch Out for These Misconceptions

• During Predict and Test: Solubility Investigations, watch for students who say the solute 'disappears' or 'melts' when it dissolves. Redirect them to evaporate the solution and recover the solid to observe that the mass and identity of the solute remain unchanged.

  After evaporating the saltwater solution, have students measure the mass of the recovered salt and compare it to the original mass. Ask them to explain how this demonstrates that dissolving is a physical change, not a chemical reaction, and record their conclusion in their lab notebooks.

• During Card Sort: Solutions, Suspensions, and Colloids, watch for students who classify mixtures based on appearance rather than particle behavior. Some may call milk a suspension because it looks uniform, or air a colloid because it contains gases.

  Ask students to shine a flashlight through each mixture. Have them observe whether light scatters (Tyndall effect) and note particle size descriptions on the cards. Require them to justify classifications using both observations and definitions from their notes.

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Methods used in this brief

• Stations Rotation
• Think-Pair-Share
• Gallery Walk