Lesson
Chemical Reactions
A nail turns to rust, a cake rises in the oven, a cold pack gets icy in seconds with no freezer. In each case, matter transformed into something brand new. How?
Driving Question
How can we tell when matter has transformed into a brand-new substance?
🔬 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:
Decide whether a change is a chemical reaction by checking one question: did a new substance form?
Tell reactants (what you start with) from products (the new substances you end up with).
Use a particle model to picture how the atoms in a reaction regroup into new substances.
Classify a reaction as exothermic or endothermic from what happens to the temperature of the surroundings.
6.MS-PS1-6
📚 Instructional Design
Why this section exists
- Set transformation as the target so students know they will explain and classify, not just recall.
- Tie each goal to its MS-PS1 standard.
Cognitive science
- Stated outcomes prime attention for the evidence and models ahead.
- Clear objectives support metacognitive self-checking.
Bloom's / DOK
- Understand to Analyze
- DOK 1 to 2
Accessibility considerations
- An icon per goal supports dual coding.
- Each goal is one short, single-action statement.
- Standard codes kept visually secondary.
Key Vocabulary
Words You'll Meet
Choose a card to see what each word means.
📚 Instructional Design
Why this section exists
- Front-load the terms students meet in the lesson body: reactant, product, exothermic, endothermic, and more.
- Pair opposites so contrasts are ready when needed.
Cognitive science
- Pre-teaching vocabulary lowers reading load later.
- Definitions stay hidden until a card is opened, reducing extraneous load.
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 Transformations. One Secret.
Look closely at three everyday events. In each one, the stuff you started with seems to vanish, and something completely different appears in its place.
The Campfire
A heavy log burns all night. By morning there's only a handful of soft gray ash, plus smoke that drifted away in the dark.
Where did most of the log go? Is ash just "broken wood"?
Click to look closer
The Instant Cold Pack
A trainer squeezes a plastic pack, shakes it, and in seconds it's icy cold - no freezer, no ice, nothing added from outside.
Where did the heat go? What made the pack cold?
Click to look closer
The Rusty Bike
A shiny silver bike is left out in the rain for a year. The metal slowly turns orange, flaky, and crumbly - and no amount of scrubbing brings the shine back.
Is rust just "dirty metal"? Why can't you scrub it off?
Click to look closer
One clue: in every case, the substance at the end is not the substance you started with. Ash is not wood. Rust is not iron. Something rebuilt the matter itself.
Compare that to melting an ice cube. The ice changes shape and state, but it's still water. What's different about the campfire, the cold pack, and the rust?
The question: burning, rusting, baking, and even the chemistry inside a cold pack all share one secret process. This lesson is about discovering that process - and learning to spot it anywhere.
📚 Instructional Design
Why this section exists
- Open with familiar events: campfire, cold pack, rust, so the new-substance idea attaches to something concrete.
- Build curiosity before any terms arrive.
Cognitive science
- Anchoring abstract chemistry in everyday phenomena builds on prior knowledge.
- Contrasting melting ice with the three mysteries pre-empts the misconception that any change is a reaction.
Bloom's / DOK
- Understand or Apply
- DOK 2
Accessibility considerations
- Each event paired with an icon and short caption for dual coding.
- High-contrast cards.
- Brief paragraphs.
Explore · The Big Idea
When Matter Becomes Something New
All three mysteries have the same answer: the atoms didn't disappear - they were rearranged into new substances.
The key idea
A chemical reaction is a process that transforms a set of chemical substances into one or more new substances. During a chemical reaction, bonds are broken and new bonds are formed between atoms.
Think about it: An ice cube melts into a puddle on the table. Is melting a chemical reaction? Make a prediction.
The test: did a NEW substance form?
Melting ice is NOT a chemical reaction, because no new substance forms. Solid water became liquid water - but it's still water, made of the same molecules. The shape and state changed; the substance did not. A real chemical reaction always produces something new, with new properties: wood becomes ash, shiny iron becomes crumbly rust.
🕵️ You be the judge. For each change below, ask the one question that matters: did a new substance form? Then click your answer.
Ice melts into water
Wood burns to ash
Paper is torn in half
A nail rusts outside
Cake batter bakes in the oven
Sugar dissolves in water
Detective work complete! You sorted all six changes. The one question that always works: did a new substance form? If yes, it's a chemical reaction. If the substance is the same and only its shape, size, or state changed, it's a physical change.
So a chemical reaction makes new substances. Scientists have a shorthand for writing down exactly what goes in and what comes out.
Time to learn to read it.
Time to learn to read it.
📚 Instructional Design
Why this section exists
- Establish the core definition: atoms rearrange into new substances.
- Resolve the shared secret behind the opening mysteries, then have students judge real cases.
Cognitive science
- The "you be the judge" sort is immediate retrieval, moving the idea from exposure to use.
- Classification practice strengthens the new-substance concept.
Bloom's / DOK
- Understand to Analyze
- DOK 2
Accessibility considerations
- Click-to-answer sorting with feedback.
- Color cues alongside text.
- Short prompts, one decision at a time.
Explore · Reading the Recipe
Writing Chemical Reactions
A chemical equation is a recipe. Follow the color coding: teal is the reactants (what you start with), green is the products (what you end with), and the gold arrow means "reacts to form."
Anatomy of a chemical equation
2H2
+
O2
→
2H2O
Left side = Reactants · present BEFORE the reaction
→ = "reacts to form"
Right side = Products · remaining AFTER the reaction
Name the parts
Reactants are the starting substances present before the chemical reaction occurs. Products are the final substances remaining after the chemical reaction occurs. Read every equation left to right: before → after.
Quick Recall
Just a quick brain check before we move on. Not graded.
In the equation CH₄ + O₂ → CO₂ + H₂O, which substances are the reactants?
Reactants → Products. But if the starting stuff disappears and something brand new appears, where did the original atoms go? Time to meet one unbreakable law of the universe.
📚 Instructional Design
Why this section exists
- Introduce chemical equations as a way to see reactants and products side by side.
- Optional background: the equation and arrow convention previews Grade 8 work (8.MS-PS1-5). At Grade 6, students are assessed on telling reactants from products and on energy transfer, not on reading or balancing equations.
Cognitive science
- Dual coding ties color-coded terms, teal reactants and green products, to the recipe metaphor.
- The familiar recipe schema scaffolds symbolic reading.
Bloom's / DOK
- Understand to Apply
- DOK 2
Accessibility considerations
- Color coding always paired with text labels, never color alone.
- Recipe analogy supports the symbols.
- Short equation examples.
Explore · Atom Rearrangement
Atoms Rearrange to Form New Substances
Atoms never vanish during a reaction, and they never appear out of nowhere. Every atom that goes in must come out - just regrouped into something new.
The unbreakable law
The Conservation of Matter means matter cannot be created or destroyed, only rearranged. The same atoms that started in the reactants are still there in the products - they have just connected to different partners to form new substances.
Atom Rearrangement Lab: Two hydrogen molecules (H₂) and one oxygen molecule (O₂) react to form water. What do you predict happens to the atoms? Pick one to unlock the lab.
⚛️ The Atom Rearrangement Lab
Hydrogen and oxygen react to form water. Watch the atoms before and after the reaction. Click Rearrange the atoms to see the same atoms regroup into water molecules.
1Count each type of atom on the reactant side BEFORE the reaction.
2Rearrange the atoms - bonds break and new bonds form.
3Recount the same atom types on the product side AFTER. They should match.
Before · Reactants
HH
HH
OO
2 H2 + O2
After · Products
Click Rearrange to see the products form.
?
Atoms before
H4
O2
Atoms after
H?
O?
Matter is conserved! The same 4 hydrogen atoms and 2 oxygen atoms that started as 2 H₂ + O₂ ended as 2 H₂O. No atom was created or destroyed - they were only rearranged into water molecules. The bonds between atoms broke and new bonds formed.
Every reaction works this way: the same atoms regroup into new substances. But something else flows through every reaction too - energy. And it can flow in two opposite directions.
📚 Instructional Design
Why this section exists
- Make atom rearrangement visible: the same atoms regroup, none vanish or appear.
- Directly counter the misconception that matter disappears during a reaction.
- Optional background: tracking atom counts to demonstrate conservation of mass is Grade 8 work (8.MS-PS1-5). Here it is enrichment that supports the Grade 6 idea of new substances forming; it is not a Grade 6 assessment target.
Cognitive science
- Model-based reasoning with explicit atom counts.
- Confronting the disappearance misconception head-on forces a belief update.
Bloom's / DOK
- Understand to Analyze
- DOK 2 to 3
Accessibility considerations
- Particle visuals paired with atom counts for dual coding.
- Step-by-step rearrangement.
- Plain-language restatement of the law.
Explore · Energy In, Energy Out
Two Types of Reactions
Remember the campfire and the cold pack from the start of the lesson? One blasted heat outward; one pulled heat inward. Every chemical reaction does one or the other.
🔥 Exothermic
Exit / Out → heat and energy leave
- Releases energy into the environment, usually as heat or light
- The temperature of the environment increases
- Signs include feeling heat, seeing light, or a temperature increase
- Examples: campfire, hand warmer, glow stick
🧊 Endothermic
Enter / In → heat and energy are absorbed
- Absorbs energy from the environment, usually as heat or light
- The temperature of the environment decreases
- The reaction soaks up energy, so the surroundings feel cooler
- Examples: instant cold pack, photosynthesis (absorbs light)
🌡️ Hold the thermometer. For each reaction below, decide: does the environment get hotter (exothermic) or colder (endothermic)?
A campfire burns
An instant cold pack is squeezed
A glow stick lights up
A hand warmer heats up
A leaf does photosynthesis
Baking soda + vinegar mix and the cup feels colder
Thermometer mastered! The trick is to watch the environment, not the reaction: if the surroundings get hotter, energy exited the reaction (exothermic). If the surroundings get colder, energy entered the reaction (endothermic).
Evidence: How to Spot a Reaction
You can't see atoms rearranging - but reactions leave clues. Watch for these four signs that a new substance may have formed.
Color Change
A shiny silver nail turns rusty orange. The new color belongs to a new substance.
Gas Produced
Bubbles fizz out of baking soda and vinegar. A brand-new gas is escaping the mixture.
Temperature Change
The mixture gets hotter (exothermic) or colder (endothermic) without any stove or freezer.
New Solid Forming
Two clear liquids are mixed and a cloudy solid appears. That solid is a new substance.
Quick Recall
One more brain check. Not graded.
You mix two liquids in a beaker. The mixture fizzes with bubbles and the beaker feels cold. What can you conclude?
Gas produced + temperature change = two pieces of evidence that new substances formed. You now have everything you need to solve the three mysteries from the start.
📚 Instructional Design
Why this section exists
- Add the energy dimension: reactions release or absorb energy, then connect back to the campfire and cold pack.
- Give students four observable signs that a reaction occurred.
Cognitive science
- The hold-the-thermometer sort uses retrieval and classification practice.
- The evidence list pre-empts "bubbles always mean boiling" and "color change always means a reaction."
Bloom's / DOK
- Understand to Analyze
- DOK 2
Accessibility considerations
- Thermometer icons and hot/cold color cues.
- Sorting with immediate feedback.
- Evidence shown as a short, scannable list.
Quick Recall
Brain Check
Three 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 3
Just a quick brain check. Not graded.
What does conservation of matter tell you about a chemical reaction?
Quick Recall · 2 of 3
Just a quick brain check. Not graded.
What does the arrow (→) in a chemical equation mean?
Quick Recall · 3 of 3
Just a quick brain check. Not graded.
An exothermic reaction does what to its surroundings?
📚 Instructional Design
Why this section exists
- Low-stakes check after the core ideas to surface gaps before the wrap-up and quiz.
Cognitive science
- Retrieval practice strengthens memory.
- Ungraded framing lowers anxiety and encourages honest attempts.
Bloom's / DOK
- Remember to Apply
- DOK 1 to 2
Accessibility considerations
- One question at a time with check-answer feedback.
- Retry option.
- Short question stems.
Explain · Wrap-Up
Back to the Three Mysteries
The campfire, the cold pack, and the rusty bike. Now you can explain every one of them like a chemist.
The Answer
All three are chemical reactions: matter was rearranged into new substances.
Wood + oxygen became ash and gases. Iron + oxygen became rust. The chemicals in the cold pack became new substances too. In each case bonds broke, new bonds formed, and the original substance was gone for good.
The Recipe
Every reaction reads the same way: reactants → products.
And the same atoms appear on both sides, because matter is conserved - rearranged, never created or destroyed.
Reactants · before
Products · after
Atoms rearrange
The Energy
The campfire and cold pack are energy opposites.
The campfire is exothermic - it releases heat and light, warming its surroundings. The cold pack is endothermic - it absorbs heat from its surroundings, which is exactly why it feels cold against your skin.
Everything in One Place
The words to know and the goals you worked toward, gathered in one spot.
| Term | Student-Friendly Definition |
|---|---|
| Chemical reaction | A process that transforms substances into new substances. Bonds are broken and new bonds are formed. |
| Reactants | The starting substances present before the reaction occurs - the left side of the equation. |
| Products | The final substances remaining after the reaction occurs - the right side of the equation. |
| Conservation of Matter | Matter cannot be created or destroyed, only rearranged. The same atoms appear in the reactants and the products. |
| Atom Rearrangement | During a reaction, bonds between atoms break and new bonds form. The atoms regroup into new substances. |
| Exothermic | A reaction that releases energy (heat or light). The environment gets warmer. Exit = out. |
| Endothermic | A reaction that absorbs energy (heat or light). The environment gets cooler. Enter = in. |
| Learning Goals | How You Showed It |
|---|---|
| Decide whether a change is a chemical reaction. | You sorted six everyday changes by asking the one question that matters: did a new substance form? |
| Tell reactants from products. | You read the color-coded anatomy of 2H₂ + O₂ → 2H₂O and identified each side of the arrow. |
| Use a particle model to picture how atoms rearrange into new substances. | In the Atom Rearrangement Lab you watched 2 H₂ + O₂ regroup into 2 H₂O - the same 4 hydrogen and 2 oxygen atoms before and after. |
| Classify reactions as exothermic or endothermic (6.MS-PS1-6). | You sorted six reactions by what happens to the temperature of the surroundings. |
Essential question: How can we tell when matter has transformed into a brand-new substance? If you can answer that with the words reactants, products, conservation of matter, and exothermic or endothermic, you own this lesson.
📚 Instructional Design
Why this section exists
- Pull every thread together: students re-explain the campfire, cold pack, and rust using the new vocabulary.
- Consolidate the pieces into one coherent model.
Cognitive science
- Returning to the opening cases closes the curiosity loop and forces transfer.
- Explaining in one's own words deepens encoding through elaboration.
Bloom's / DOK
- Understand to Analyze
- DOK 2 to 3
Accessibility considerations
- Reference table of terms and goals gathered in one place.
- Essential question restated.
- Short, structured prompts.
Evaluate · Quiz
Check Your Understanding
Ten questions covering everything you discovered, including equations for you to check. 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 that a chemical reaction has happened, and how you would decide whether that reaction is exothermic or endothermic by watching the energy move between the reaction and its surroundings.
One strong way to say it
A chemical reaction has happened when a brand-new substance forms - you see signs like a new gas, a new color, a new solid, or a temperature change - and you classify it by which way the energy moves: it is exothermic if the reaction releases thermal energy and warms its surroundings, or endothermic if it absorbs thermal energy and cools its surroundings. If your sentence names the new-substance test and says which way heat moves, you have it.
🔍 The Mystery You Came In With
You started this lesson with one question: "How can we tell when matter has transformed into a brand-new substance?" If you can explain reactants, products, conservation of matter, and exothermic vs endothermic, you've solved the mystery.
📚 Instructional Design
Why this section exists
- Ten-question check across evidence a reaction occurred, observable changes, and energy transfer (exothermic vs endothermic).
- Confirm the Grade 6 objectives (6.MS-PS1-6) were met.
Cognitive science
- Spaced retrieval across the whole lesson.
- Answer explanations turn the quiz into a feedback loop, not just a score; distractors target physical-vs-chemical and disappearing-matter confusions.
Bloom's / DOK
- Understand to Apply
- DOK 1 to 2
Accessibility considerations
- One question per item with a clear submit flow.
- Try-again reset.
- Plausible distractors of varied length.
Go Further
More Learning
You saw how reactions rearrange atoms into brand-new substances while mass is conserved. Take that thinking off the screen and put it to work with a hands-on challenge at home.
Extension
Reaction Hunt
Hunt for three chemical reactions in your kitchen tonight and write the evidence for each (color change? gas? temperature change? new solid?). Then sketch a particle model that shows the atoms in baking soda + vinegar rearranging into new products, and label which atoms ended up where.
Extension
The Hidden World of Matter
Curious what those rearranging atoms really are? Look ahead to a big Grade 8 idea and zoom in past what your eyes can see to meet the atoms and elements that build every substance.
Explore
📚 Instructional Design
Why this section exists
- Offer a hands-on challenge that extends conservation and reaction ideas at home.
- Keep momentum after the lesson.
Cognitive science
- Spacing and interleaving across units strengthen retention.
- Transfer: students find and model reactions in their own kitchen.
Bloom's / DOK
- Apply to Analyze
- DOK 2 to 3
Accessibility considerations
- Card layout with icon, category, and short description.
- Large tap targets.
- Clear link labels.
Connections
Connections
These lessons build on what you just learned about chemical reactions.