Home›Lesson Plans›Science›Physical Science · Grade 8

Chemical Reactions: When Atoms Rearrange

Students learn what happens in a chemical reaction — reactants transform into new products while atoms are conserved — and how to spot the signs that a reaction has occurred.

Grade 8Chemistry55 minutes1 class period5E ModelExplicit teaching4 StandardsCommon Core
Start the Lesson
Lesson at a Glance

Everything you need before the bell rings

Learning Objectives

Students will be able to…

  • ✓Identify reactants and products.
  • ✓Recognize signs of a reaction.
  • ✓Explain conservation of mass.
  • ✓Understand why equations are balanced.
Essential Question

When wood burns or iron rusts, new substances appear — but no atoms are lost. How do chemical reactions transform matter while conserving every atom?

0
Lesson Phases
0
Vocabulary Terms
0
Standards Aligned
0
Interactive Task
Reaction Explorer · Interactive

The Reaction Explorer

Project this and tap each part. Have students learn how reactants become products and why the mass never changes.

⚗️ Explore chemical reactions — tap eachTry it

The Lesson · 5E Model

55 minutes, five moves

Tap any phase to open the teacher moves and student actions.

1

Engage — New Stuff, Same Atoms

5 min

Burn wood — you get ash, gas, heat. Where did the atoms go?

👩‍🏫 Teacher Moves

  • Show a reaction (rust, burning).
  • Ask where the atoms went.
  • Set the goal: chemical reactions.

🎒 Student Actions

  • Observe the change.
  • Wonder about atoms.
  • Predict the idea.
2

Explore — Explore Reactions

12 min

Students investigate.

👩‍🏫 Teacher Moves

  • Send students to the Reaction Explorer.
  • Record each part.
  • Note the signs.

🎒 Student Actions

  • Tap each part.
  • Record it.
  • List the signs.
3

Explain — Atoms Are Conserved

13 min

Teacher explains.

👩‍🏫 Teacher Moves

  • Explain reactants → products.
  • Explain conservation of mass.
  • Show why equations balance.

🎒 Student Actions

  • Explain the change.
  • Explain conservation.
  • Explain balancing.
4

Elaborate — Balance It

12 min

Apply.

👩‍🏫 Teacher Moves

  • Balance a simple equation.
  • Verify mass is conserved.
  • Classify a reaction type.

🎒 Student Actions

  • Balance an equation.
  • Check the mass.
  • Classify it.
5

Evaluate — Exit Ticket

5 min

Three quick checks.

👩‍🏫 Teacher Moves

  • Hand out the exit ticket.
  • Look for conservation of mass.
  • Collect as formative data.

🎒 Student Actions

  • Name reactants/products.
  • Explain conservation.
  • Name a sign.
Standards Alignment

Built to the standards you report on

Aligned to Next Generation Science Standards and Common Core literacy. State-standard crosswalks available on request.

NGSS
MS-PS1-2

Analyze data on properties before and after substances interact to determine if a chemical reaction occurred.

NGSS
MS-PS1-5

Develop a model to describe that atoms are conserved in a chemical reaction.

NGSS
MS-PS1-4

Develop a model describing changes in particle motion and state.

CCSS
RST.6-8.3

Follow precisely a multistep procedure in a scientific text.

Differentiation

One lesson, every learner

Multilingual Learners

ELL / EMERGING READERS
  • Reactant/product model with atoms.
  • Sentence frame: “The ___ became ___.”
  • Count atoms on both sides.

Support & Access

IEP / 504
  • Focus on signs of a reaction.
  • Use a simple word equation.
  • Count atoms with models.

Stretch & Extend

GIFTED / EARLY FINISHERS
  • Balance a harder equation.
  • Explain endothermic vs. exothermic.
  • Design a conservation-of-mass test.
Materials

What to gather

  • 📽️Projector / board
  • 📓Science notebooks
  • 💻The Reaction Explorer
  • 🧪Baking soda + vinegar
  • ⚖️A balance scale
  • 🎫Exit-ticket slips
Vocabulary

Key terms — hover for a quick definition

chemical reactiona process that forms new substancesreactanta starting substanceproducta substance formedconservation of massmass stays the same in a reactionbalanced equationequal atoms on both sidessynthesiscombining substancesdecompositionbreaking a substance apartprecipitatea solid formed in a reaction
Evaluate

Exit Ticket

Preview the three formative checks. Tap “Sample answer” to see what mastery looks like — hide them before you print for students.

QUESTION 1
In a chemical reaction, what are reactants and products?
Reactants are the starting substances; products are the new substances formed.
QUESTION 2
What does the law of conservation of mass say?
Matter is never created or destroyed — the mass of the reactants equals the mass of the products.
QUESTION 3
Name one sign that a chemical reaction has occurred.
Any one of: color change, bubbles/gas, temperature change, light, new smell, or a solid (precipitate).

Going deeper? Prove conservation of mass.

Have students mass a sealed reaction (like baking soda and vinegar in a closed bag) before and after to show the mass stays the same. A printable lab sheet is in the Science library.

Study · Flashcards

Study the key terms

Tap a card to flip it, then rate whether you knew it. Built from this lesson’s vocabulary.

🃏 Chemical ReactionsFlip
Card 1
Term
Tap to flip →
Meaning
0

Nice work!

Practice · Quiz

Check your understanding

A quick self-check with instant feedback, drawn from this lesson’s key terms.

📝 Chemical ReactionsQuiz
Score: 0
1 / 6
Question 1
0%

Nice work!

Practice · Worksheet

Printable worksheet

A print-and-go review sheet with a built-in answer key. Tap “Show answer key” to reveal answers, or print the clean version for students.

🖨️ Chemical ReactionsPrint
Name: ________________________
Date: ____________

Part A · Write the word that matches each meaning

Word bank: balanced equation, chemical reaction, conservation of mass, decomposition, precipitate, product, reactant, synthesis
  1. equal atoms on both sides
  2. a solid formed in a reaction
  3. a starting substance
  4. a process that forms new substances
  5. mass stays the same in a reaction
  6. breaking a substance apart
  7. a substance formed
  8. combining substances

Part B · Show what you learned

  1. In a chemical reaction, what are reactants and products?
  2. What does the law of conservation of mass say?
  3. Name one sign that a chemical reaction has occurred.
Answer key — Part A: 1) balanced equation · 2) precipitate · 3) reactant · 4) chemical reaction · 5) conservation of mass · 6) decomposition · 7) product · 8) synthesis
Part B: 1) Reactants are the starting substances; products are the new substances formed. 2) Matter is never created or destroyed — the mass of the reactants equals the mass of the products. 3) Any one of: color change, bubbles/gas, temperature change, light, new smell, or a solid (precipitate).