Types of Mixtures: Solutions, Suspensions, Colloids

Active learning helps students grasp the invisible differences between mixtures by making particle behavior tangible. When students create, observe, and separate mixtures themselves, they build lasting mental models of solutions, suspensions, and colloids that go beyond textbook definitions.

• Grade 6
• Science
• 4 activities
• 25 min–45 min

Learning Objectives

1. Classify common substances as solutions, suspensions, or colloids based on their observable properties.
2. Compare the particle behavior and separation methods for solutions, suspensions, and colloids.
3. Design an experiment to differentiate between a solution and a suspension using filtration and observation over time.
4. Explain how the size of particles in a mixture affects its stability and appearance, referencing the Tyndall effect.
5. Analyze the characteristics of a given mixture to determine if it is homogeneous or heterogeneous.

Inquiry Circle

⏱ 45 min·Small Groups

Lab Stations: Mixture Creation

Prepare stations for salt water (solution), sand water (suspension), and cornstarch water (colloid). Small groups mix ingredients, record initial appearance, then let sit for 10 minutes to check settling. Shine flashlights through each to test Tyndall effect.

Prepare & details

Compare the characteristics of solutions, suspensions, and colloids.

Facilitation Tip: During Lab Stations: Mixture Creation, prepare exact measurements for each mixture so students focus on observations rather than recipe errors.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Inquiry Circle

⏱ 30 min·Pairs

Filtration Challenge: Pairs

Pairs filter samples of a solution, suspension, and colloid using coffee filters and funnels. Note residue on filters and clarity of filtrate. Discuss how particle size predicts results and sketch findings.

Prepare & details

Design an experiment to distinguish between a solution and a suspension.

Facilitation Tip: In Filtration Challenge: Pairs, circulate with a timer to ensure teams record data consistently so comparisons are valid.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Inquiry Circle

⏱ 40 min·Whole Class

Shake and Observe Demo: Whole Class

Demonstrate shaking jars of each mixture type, then observe settling over 20 minutes as a class. Students predict and time settling, then share data on class chart. Extend with student-led predictions for new mixtures.

Prepare & details

Explain how particle size influences the properties of different mixtures.

Facilitation Tip: For Shake and Observe Demo: Whole Class, dim lights when testing for the Tyndall effect to make light scattering unmistakable.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Inquiry Circle

⏱ 25 min·Individual

Particle Size Sort: Individual

Provide images or samples of particles from fine salt to sand. Individuals sort by estimated size, predict mixture type, then test one prediction by mixing. Compare results in plenary.

Prepare & details

Compare the characteristics of solutions, suspensions, and colloids.

Facilitation Tip: During Particle Size Sort: Individual, provide a reference chart with visual particle sizes so students connect labels to real examples.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Teaching This Topic

Teach this topic by starting with what students already know about mixtures, then layer in new vocabulary and tools like microscopes or flashlights. Avoid rushing to the terms solutions, suspensions, and colloids before students see the differences themselves. Research shows students learn best when they first manipulate materials, then name their observations, rather than memorizing definitions up front.

What to Expect

Successful learning looks like students confidently classifying mixtures by particle size, predicting behavior like settling or light scattering, and justifying choices with evidence from their hands-on work. Clear labeling, careful observations, and collaborative discussions show growing mastery of the distinctions.

Watch Out for These Misconceptions

Common Misconception

During Lab Stations: Mixture Creation, watch for students assuming all mixtures settle over time.

What to Teach Instead

Ask students to predict which mixtures will settle before leaving the station, then have them time their jars and record results in a shared class table to compare outcomes.

Common Misconception

During Shake and Observe Demo: Whole Class, watch for students calling colloids solutions because they look uniform at first.

What to Teach Instead

Pass flashlights around so every student sees the Tyndall effect in colloids like milk or gelatin, then ask them to revise their labels as a class.

Common Misconception

During Filtration Challenge: Pairs, watch for students thinking particle size does not affect filtration.

What to Teach Instead

Have pairs compare filter papers after separating mixtures, then sketch the trapped particles to connect size to separation success.

Assessment Ideas

Exit Ticket

After Lab Stations: Mixture Creation, give students three labeled beakers (water, salt water, muddy water) and ask them to write one observation for each that classifies it correctly.

Quick Check

During Filtration Challenge: Pairs, circulate and ask each pair to explain why their filter trapped particles in the suspension but not in the solution.

Discussion Prompt

After Shake and Observe Demo: Whole Class, pose the question: 'How would your separation method change if the mixture were a colloid instead of a suspension?' and facilitate a 5-minute class discussion.

Extensions & Scaffolding

• Challenge students to design a mixture that behaves like a colloid but changes to a suspension when heated, using household materials like cornstarch and water.
• Scaffolding: Provide pre-labeled jars with lids for students who struggle to keep mixtures organized during stations.
• Deeper exploration: Have students research how emulsifiers work in colloids like mayonnaise, then test a homemade version in class.

Key Vocabulary

Solution	A homogeneous mixture where one substance dissolves completely into another, forming a clear, uniform appearance. Solute particles are too small to be seen and do not settle out.
Suspension	A heterogeneous mixture containing solid particles that are sufficiently large to settle out over time or be filtered. The mixture appears cloudy or opaque.
Colloid	A mixture with particles larger than those in a solution but smaller than those in a suspension. These particles remain dispersed and scatter light, but do not settle out easily.
Tyndall Effect	The scattering of a light beam by the large particles in a colloid or suspension, making the beam visible. Solutions do not exhibit this effect.
Homogeneous Mixture	A mixture that has a uniform composition and appearance throughout. Solutions are examples of homogeneous mixtures.
Heterogeneous Mixture	A mixture that does not have a uniform composition. Different parts of the mixture may have different properties. Suspensions and colloids are examples.