🧂 🥤 🧲 🥣

Lesson

Pure Substances & Mixtures

You stir a spoonful of salt into water and it disappears completely. Salad dressing splits into layers all by itself. A magnet pulls metal right out of sand. What's going on?

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Driving Question

When salt vanishes into water, is it gone forever - or can you get it back?

🔬 Learning Science Focus 🔍 Phenomenon First 🏷️ Label After Learning 🪜 Stepwise Scaffolds ✏️ Generation Effect ✅ Retrieval Practice

Learning Goals

What You'll Be Able to Do

By the end of this lesson, you will be able to:

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Classify a sample of matter as a pure substance, a homogeneous mixture, or a heterogeneous mixture - and explain your reasoning using particles.

6.MS-PS1-8(MA)

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Choose the right physical method - filtration, evaporation, magnetism, or sieving - to separate a mixture back into its parts.

6.MS-PS1-8(MA)

📚 Instructional Design

Why this section exists

Set the two outcomes up front: classify matter, and choose a separation method.
Tie both goals to one standard, 6.MS-PS1-8(MA), so the lesson stays in scope.

Cognitive science

Goal setting primes attention for the classify-then-separate arc.
Advance organizer: students know the target before the content.

Bloom's / DOK

Understand to Analyze
DOK 2 to 3 (goals ask students to classify and explain reasoning with particles)

Accessibility considerations

Two cards only, large targets, no overload.
Plain "be able to" wording.
Standard code shown but not required reading.

Key Vocabulary

Words You'll Meet

Choose a card to see what each word means.

📚 Instructional Design

Why this section exists

Front-load the nine terms students will meet in the lesson body.
Define separation tools alongside the matter categories so labels are ready when needed.

Cognitive science

Pre-teaching vocabulary lowers reading load later.
Reduced extraneous load: definitions stay hidden until a card is opened.

Bloom's / DOK

Remember to Understand
DOK 1

Accessibility considerations

Click to reveal, no hover.
One short definition per card.
Color-coded cards match the section colors used later.

Engage · Mystery

Three Kitchen Mysteries

No lab needed for this one - your kitchen is already full of strange behavior. Look closely at these three everyday items.

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The Salad Dressing

Shake a bottle of oil-and-vinegar dressing and it blends. Set it down, and within minutes it splits back into layers all by itself.

Why won't the oil and vinegar stay combined?

Click to look closer

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The Coffee

A cup of coffee looks exactly the same from the first sip to the last. Every drop tastes identical - yet it's made of water plus dissolved coffee.

If it's two things combined, why can't you see the parts?

Click to look closer

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The Vanishing Salt

Stir a spoonful of salt into a glass of water. The salt completely disappears. No filter, strainer, or spoon can scoop it back out.

Is the salt gone forever - or hiding?

Click to look closer

💡 One clue: in every case, the original ingredients are still there - their particles just combined without chemically joining.

🤔 If the particles never joined, there should be a way to pull them apart again. What tool would get the salt back out of the water?

The question: Some matter is one ingredient through and through. Some is a combination wearing a disguise. This lesson is about telling them apart - and learning four tools to un-mix the combinations.

📚 Instructional Design

Why this section exists

Anchor the unit in three familiar kitchen behaviors students cannot yet explain.
Seed the driving question that the synthesis section pays off.

Cognitive science

Curiosity gap: each card poses a "why" before any answer.
Phenomenon-based learning grounds abstract categories in real objects.

Bloom's / DOK

Understand
DOK 2

Accessibility considerations

Click to look closer, no hover.
Everyday objects need no prior science.
Short observation and question on each card.

Explore · One Ingredient Only

What Is a Pure Substance?

Imagine zooming in on a sample of matter until you can see its particles. In some samples, every single particle is identical - the same ingredient, everywhere you look.

The key idea

A pure substance is a sample of matter that has the same ingredients throughout. Pure substances have only one type of particle: an element, a molecule, or a compound.

Element

One kind of atom, on its own
Example: sodium (Na)

Molecule

Atoms bonded into pairs or groups
Example: chlorine gas (Cl₂)

Compound

Different atoms chemically joined
Example: table salt (NaCl)

All three are pure substances The test: every particle in the sample is the same

Pure substances you might recognize:

💧Distilled water (H₂O)

🥇24-karat gold (Au)

🧂Pure table salt (NaCl)

🍬Pure sugar

🎈Helium in a balloon (He)

✏️Graphite in a pencil (C)

But most matter isn't pure. Salt water, coffee, salad dressing, soup, even the air you're breathing - they're all combinations.

So what do we call matter with more than one type of particle? Let's find out.

📚 Instructional Design

Why this section exists

Define the baseline category, pure substance, before introducing mixtures.
Show that element, molecule, and compound all share one test: every particle is the same.

Cognitive science

Dual coding: labeled particle diagrams paired with the definition.
Concrete to abstract: named examples follow the particle model.

Bloom's / DOK

Understand
DOK 2 (read particle diagrams to recognize the "same particle" pattern)

Accessibility considerations

Diagrams carry aria-labels describing each model.
Familiar example chips (gold, salt, sugar) anchor the term.
One key-idea card states the definition plainly.

Explore · Combined But Not Joined

What Is a Mixture?

Back to the salad dressing from the mystery. The oil and vinegar were shaken together - but did they ever truly become one new substance?

🤔

Think about it: When you shake oil and vinegar together, what happens to their particles? Make a prediction.

Here's the answer

The particles stay separate - they never chemically join. A mixture contains different particles that are not chemically joined. Because the parts never joined, they can be separated physically. In salad dressing, the oil and vinegar can be physically separated by density: the less dense oil floats to the top and forms its own layer.

🥗 Salad dressing: shake it all you want - gravity sorts the layers back out by density, because the particles were never chemically joined.

🔑 The big rule: if you can pull it apart with physical tools (settling, filters, magnets, heat), it's a mixture - not a pure substance.

One puzzle solved. But wait - the coffee never separated into layers, and the salt water looks like plain water.

Not all mixtures look mixed. It turns out there are two types.

📚 Instructional Design

Why this section exists

Define mixture as combined but not chemically joined, so the parts stay separable.
Use one mystery (salad dressing) to make the definition concrete.

Cognitive science

Generation effect: students predict before the answer unlocks.
Misconception checking: the predict options confront the idea that combining creates a new substance.

Bloom's / DOK

Understand
DOK 2

Accessibility considerations

Definition stays gated until a prediction is made, reducing skim-ahead.
Click options, no hover or typing.
Key terms bolded in place.

Explore · Two Types of Mixtures

Homogeneous vs. Heterogeneous

Compare the two beakers below. Both hold mixtures - but look at how the particles are spread out. Follow the color coding: green is homogeneous and orange is heterogeneous.

Homogeneous Mixture

Different substances that are evenly distributed
The prefix "homo" means one or same throughout
Looks like one thing - you can't see the separate parts
Examples: coffee, salt water, air

Heterogeneous Mixture

Different substances that are UNevenly distributed
The prefix "hetero" means many or different parts you can see
You can see (or find) the separate chunks
Examples: chicken soup, salad dressing, trail mix

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Memory trick: hetero starts like "heterogeNOPE - those parts are NOT spread evenly." If every spoonful is different (chicken soup), it's heterogeneous. If every sip is identical (coffee), it's homogeneous.

🥣 The Mixture Sorter

Five mixtures are coming through the lab. For each one, ask: are the parts spread evenly (every bite or sip the same) or unevenly (you can see or find different parts)? Then sort it.

🏆 All five sorted! You can now classify any mixture by asking one question: are the parts spread evenly or unevenly?

So the coffee and the salt water are homogeneous mixtures - combined, but never chemically joined.

And that's the key to the salt mystery. If the particles never joined, we can pull them apart. Time to open the toolbox.

📚 Instructional Design

Why this section exists

Split mixtures into homogeneous and heterogeneous using one question: evenly or unevenly spread.
Move students from recognizing the categories to sorting real examples into them.

Cognitive science

Comparison and contrast: side-by-side beakers and parallel lists.
Dual coding: particle diagrams paired with traits.
Classification practice in the Mixture Sorter.

Bloom's / DOK

Understand to Analyze
DOK 2 (classify and compare across categories)

Accessibility considerations

Side-by-side cards with short, parallel bullets.
Sorter gives immediate feedback per item.
Color coding reinforced by labels, not color alone.

Explore · The Separation Toolbox

Separating Mixtures

Mixtures can be separated physically - no chemistry required. Here are four tools, each matched to a different kind of mixture. The trick is choosing the tool that targets a difference between the parts: size, state, or magnetism.

Method 1

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Filtration

Filtration separates big particles from small particles using a filter - like a coffee filter trapping the grounds while the liquid drips through.

Targets: particle size (solid in liquid)

Method 2

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Evaporation

Evaporation removes a liquid by turning it into gas, leaving solids behind - even solids that dissolved and "vanished."

Targets: liquid vs. dissolved solid

Method 3

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Magnetism

Magnetism separates a mixture when one part is magnetic and the others are not - the magnet grabs only the magnetic part.

Targets: magnetic vs. non-magnetic

Method 4

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Sieving

Sieving separates mixtures using a tool with holes of a specific size (a sieve or mesh) - small pieces fall through, big pieces stay on top.

Targets: particle size (solid in solid)

How do you pick the right tool? Watch one worked example, step by step. Mixture: muddy water (dirt + water).

Step 1 · Name the parts

What is in the mixture? Solid dirt particles floating in liquid water.

Step 2 · Find a difference

The dirt particles are big; water particles are tiny. A size difference!

Step 3 · Match the tool

A size difference between solid and liquid means...

Filtration ☕

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See the pattern? Name the parts → find a difference → match the tool. Now it's your turn to run the lab.

🧪 The Separation Lab

Four mixtures need un-mixing. Use the three steps: name the parts, find a difference, match the tool. Pick the best method for each mixture.

Mixture 1 Mixture 2 Mixture 3 Mixture 4

🏆 Lab complete! You separated all four mixtures - proof that mixtures are combined physically, never chemically joined.

Notice what just happened with the salt water. No filter could catch the dissolved salt - the particles were too small. But evaporation removed the water as gas and left every grain of salt behind.

The vanishing salt was never gone. It was just mixed.

📚 Instructional Design

Why this section exists

Deliver the lesson's second goal: choose a physical separation method.
Give a repeatable plan, name the parts, find a difference, match the tool.

Cognitive science

Worked example models the reasoning before the lab.
Cause-and-effect: each tool targets a specific difference between parts.
Productive struggle in the Separation Lab applies the plan.

Bloom's / DOK

Understand to Analyze
DOK 2 to 3 (students reason from a difference to justify which tool fits)

Accessibility considerations

Worked steps shown before students try alone.
Tool buttons with icon and name, large targets.
Per-mixture feedback explains the match.

Quick Recall

Brain Check

Two quick questions before we put it all together. These are not graded. Pulling answers from memory now will help them stick.

Quick Recall · 1 of 2

A quick brain check. Not graded.

A glass of lemonade (no pulp) tastes exactly the same from the first sip to the last. What is it?

A pure substance - it looks like one thing A homogeneous mixture - different substances, evenly distributed A heterogeneous mixture - you could see the parts with a microscope

Quick Recall · 2 of 2

One more brain check. Not graded.

Why does shaken salad dressing separate back into layers, while salt water never does?

Salad dressing is heterogeneous - its parts separate physically by density. Salt water is homogeneous - the salt stays evenly spread. The salt chemically joined with the water, but the oil never joined the vinegar Salad dressing is a pure substance, so it always returns to its original form

📚 Instructional Design

Why this section exists

Check classification and the separable-because-not-joined idea before the quiz.
Catch shaky understanding while it is still low stakes.

Cognitive science

Retrieval practice strengthens memory more than rereading.
Feedback loops: check, then retry on a miss.

Bloom's / DOK

Understand to Apply
DOK 1 to 2 (first item recalls a category, second explains why behaviors differ)

Accessibility considerations

Ungraded and clearly marked not graded.
Immediate, polite-announced feedback.
Try Again removes penalty for a first miss.

Explain · Wrap-Up

Back to the Kitchen Mysteries

You started this lesson with three strange kitchen items. Now you can explain every one of them like a chemist.

The Answer

The salt was never gone - it was mixed, not joined.

Salt water is a homogeneous mixture: salt particles spread evenly through the water, too small for any filter. But because the particles never chemically joined, evaporation gets every grain back.

The Classification

All matter sorts into three groups.

Pure substance (one type of particle throughout), or one of two mixture types:

Homogeneous · evenly spread Heterogeneous · unevenly spread

The Toolbox

Mixtures can always be un-mixed physically.

Match the tool to the difference between the parts:

☕ Filtration ☀️ Evaporation 🧲 Magnetism 🕸️ Sieving

Everything in One Place

The words to know and the goals you worked toward, all in one spot.

Term	Student-Friendly Definition
Pure substance	A sample of matter that has the same ingredients throughout - only one type of particle (element, molecule, or compound).
Mixture	Different particles that are not chemically joined. The parts can be separated physically.
Homogeneous mixture	Different substances that are evenly distributed ("homo" = one or same throughout). Example: coffee.
Heterogeneous mixture	Different substances that are UNevenly distributed ("hetero" = many different parts you can see). Example: chicken soup.
Filtration	Separates big particles from small particles using a filter (like a coffee filter).
Evaporation	Removes a liquid by turning it into gas, leaving solids behind.
Magnetism	Separates a mixture when one part is magnetic and the others are not.
Sieving	Separates mixtures using a tool with holes of a specific size (a sieve or mesh).

Learning Goals	How You Showed It
Classify matter as a pure substance, homogeneous mixture, or heterogeneous mixture (6.MS-PS1-8(MA)).	You read particle diagrams of elements, molecules, and compounds, then sorted five real mixtures by asking whether their parts were spread evenly or unevenly.
Choose the right physical method to separate a mixture into its parts (6.MS-PS1-8(MA)).	You used the three-step plan (name the parts, find a difference, match the tool) to separate four mixtures with filtration, evaporation, magnetism, and sieving.

Essential question: How can you tell whether a sample of matter is one ingredient or a combination - and how would you get the parts back? If you can answer that with the words mixture, homogeneous, heterogeneous, and one separation method, you own this lesson.

📚 Instructional Design

Why this section exists

Resolve the opening mysteries and tie classification to separation in one place.
Collect terms and goals in summary tables for review.

Cognitive science

Coherent narrative closes the loop opened in Engage.
Schema building: the three beats connect into one framework.
Misconception checking: "the salt was never gone" confronts the disappearing-matter idea.

Bloom's / DOK

Understand to Analyze
DOK 2 to 3 (connects category and method to explain a phenomenon)

Accessibility considerations

Summary tables put terms and goals in one scannable spot.
Short beat answers before fuller explanation.
Essential question restates the target in plain words.

Evaluate · Quiz

Check Your Understanding

Ten questions covering everything you discovered, including new samples to classify and new mixtures to separate. Answer every question, then submit.

Your score will not be sent Your score will be sent to your teacher

0 / 10 selected

🧠 Show Your Thinking

Scientists don't just know the answer. They explain their thinking.

Write your own explanation first. Then submit your work to compare your thinking with a model answer.

In one sentence, explain how you can tell whether a sample is a pure substance or a mixture, and why that tells you whether its parts can be separated by physical methods like evaporation or filtration.

One strong way to say it A sample is a mixture when it is two or more substances physically blended together with each part still keeping its own properties, while a pure substance is a single kind of matter all the way through - and because a mixture's parts are only physically combined and never chemically changed, you can pull them back apart with physical methods like evaporation, filtration, or magnetism. If your sentence says a mixture's parts keep their own properties and can be separated by physical means, you have it.

🔍 The Mystery You Came In With You started this lesson with one question: "When salt vanishes into water, is it gone forever - or can you get it back?" If you can explain why salt water is a mixture and how evaporation gets the salt back, you've solved the mystery.

📚 Instructional Design

Why this section exists

Measure both goals on new samples to classify and new mixtures to separate.
Support practice (self-check) and classroom (submitted) use from one quiz.

Cognitive science

Retrieval practice on fresh items, not memorized ones.
Feedback loops: answer explanations follow scoring.

Bloom's / DOK

Understand to Apply
DOK 1 to 2 (recognize categories, apply the matching rule to new cases)

Accessibility considerations

Practice mode works with no submission required.
Progress bar and disabled submit until complete.
Plausible, evenly placed options with explanations.

Go Further

More Learning

You learned to tell pure substances and mixtures apart and pull mixtures back into their parts. Take that thinking off the screen and put it to work with a hands-on challenge at home.

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Extension

Kitchen Separation Lab

Design a separation plan for trail mix that has iron-fortified cereal in it (hint: you will need more than one tool). Then hunt through your kitchen and classify five items as pure substance, homogeneous mixture, or heterogeneous mixture, and defend each call to a partner.

📚 Instructional Design

Why this section exists

Offer next steps that build on classifying and separating matter.
Pose challenges that need more than one tool or a defended classification.

Cognitive science

Transfer: apply the framework to a multi-step mixture and to kitchen items.
Interest-driven extension keeps momentum past the lesson.

Bloom's / DOK

Apply to Analyze
DOK 2 to 3 (design a multi-tool plan and defend each classification)

Accessibility considerations

Optional and self-paced, no penalty for skipping.
Cards labeled by type with clear next-step links.
Challenges use household materials, no special equipment.

Connections

These lessons build on what you just learned about pure substances and mixtures.

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Extension

The Hidden World of Matter

Pure substances are made of elements, molecules, and compounds. Want to look ahead? Zoom in one more level and meet the atoms that build them all.

Mixing makes a mixture, but a reaction makes a whole new substance. See what happens when atoms rearrange into something different.

Explore