You will learn
- Classify changes.
- Give evidence.
- Explain with particles.
- Predict outcomes.
Version 0.2 · expanded edition · built from cited public sources Content is based on the official frameworks and sources listed under Sources and standards. No official endorsement is claimed. Written in the style of common primary school assessments. No exam result is promised.
Student lesson
- Physical changes are usually reversible.
- Chemical reactions are irreversible.
- Signs include bubbles, colour change, heat or light.
- Particles rearrange in reactions.
Words to know
a change that can be undone
a change that cannot be undone
a change that makes new substances
a sign that something happened
1. Discover: The fizzing powder
Adwoa stirs baking soda into vinegar and the mixture fizzes. The bubbles are a new gas. “You cannot turn that fizz back into baking soda and vinegar,” her teacher says. “It is irreversible.”
Think: What was the evidence?
2. Understand: Changes
Idea 1: Reversible
Reversible changes include melting, freezing, dissolving and evaporating. The particles are the same, only arranged differently.
Idea 2: Irreversible
In a chemical reaction such as burning, baking, rusting or fizzing, particles rearrange into new substances. These changes are irreversible.
Idea 3: Evidence
Signs of a reaction: gas bubbles, colour change, heat or light given out, a new solid forming or a new smell.
3. Worked examples
Example 1 (I show you): Classify
Melting ice.
- Back to ice.
- Same substance.
- Reversible.
Answer: Reversible.
Example 2 (We do it together): Classify
Baking.
- New substance.
- Cannot undo.
- Irreversible.
Answer: Irreversible.
Example 3 (You try): Evidence
Fizz.
Show the steps and answer
- Bubbles.
- Gas.
- New substance.
Answer: New gas shows a reaction.
Did you know?
Every time you cook an egg, new substances form that cannot be turned back into raw egg.
Why this matters
Knowing about changes helps us cook, build and protect materials.
4. Explore: Change sort
With an adult, mix a teaspoon of baking soda into vinegar in a tray outdoors and observe, then sort 12 change cards.
- Wear glasses.
- Adult measures vinegar and soda.
- Observe bubbles.
- Sort the cards.
Think about it: what did you notice?
What did you notice? Fizzing showed a new gas; melting and dissolving were reversible.
5. Practise
Say it in a sentence
Use these starters when you talk about the lesson. Say them out loud.
- A ___ change can be undone.
- An ___ change cannot be undone.
- A chemical ___ makes new substances.
- ___ is a sign something happened.
Guided practice
Question 1. What is reversible?
Can undo.
Question 2. What is irreversible?
Cannot undo.
Question 3. What is a reaction?
New substances.
Independent practice
Level 1: Start
- What is reversible?
- What is irreversible?
- What is a reaction?
- Name a sign.
- Name a reversible change.
Level 2: Grow
- Why is baking irreversible?
- Why is melting reversible?
- Why evidence?
Level 3: Stretch
- Sort the cards.
- Observe fizz.
- Explain.
Answers are in the answer key below. Try first, then check.
6. Apply: Science in everyday life
Explain why toast cannot become bread again.
Show a sample answer
Use evidence.
Another one. Tell a family member one thing from this lesson. Use the words you learned.
Show a sample answer
A clear sentence that uses at least one word from Words to know.
7. Common mistakes
Fix: Some cannot.
Fix: Reversible.
8. Lesson summary and revision card
- I can classify changes.
- I can give evidence.
- I can explain with particles.
- I can predict outcomes.
9. Check and master
Answer all 14 questions. You will see feedback after each one.
Your result appears here after you answer every question.
10. Key takeaways
- Physical changes are usually reversible.
- Chemical reactions are irreversible.
- Signs include bubbles, colour change, heat or light.
- Particles rearrange in reactions.
11. Next lesson
Next lesson: What is energy?. Keep going with the next idea in this course.
Exam practice
These questions are written in the style of common school and international primary assessments. Try them on your own, without looking back. Then check your answers in the marking guide. The marks are shown in brackets.
- Define reversible, irreversible and reaction. [3 marks]
- Sort four changes. [4 marks]
- Give evidence of a reaction. [1 mark]
- Safety rule. [2 marks]
Total: 10 marks.
Marking guide and model answers
- 1 each
- 1 each
- One sign
- Any [1]; reason [1]
Score guide: 9 to 10 = secure. 6 to 8 = nearly there, revise the parts you missed. Under 6 = work through the lesson again with a grown-up.
Printable worksheet
- What is reversible?
- What is irreversible?
- What is a reaction?
- Name a sign.
- Name a reversible change.
- Why is baking irreversible?
- Why is melting reversible?
- Why evidence?
- Sort the cards.
- Observe fizz.
Homework
List five changes at home and sort them.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| 1. What is reversible? | Can undo. | 1 |
| 2. What is irreversible? | Cannot undo. | 1 |
| 3. What is a reaction? | New substances. | 1 |
| 4. Name a sign. | Bubbles. | 1 |
| 5. Name a reversible change. | Melting. | 1 |
| 6. Why is baking irreversible? | New substance. | 1 |
| 7. Why is melting reversible? | Same substance. | 1 |
| 8. Why evidence? | Prove change. | 1 |
| 9. Sort the cards. | Table. | 1 |
| 10. Observe fizz. | Notes. | 1 |
| Total | 10 |
Independent practice answers. Level 1: 1 Can undo.; 2 Cannot undo.; 3 New substances.; 4 Bubbles.; 5 Melting.. Level 2: 1 New substance.; 2 Same substance.; 3 Prove change.. Level 3: 1 Table.; 2 Notes.; 3 Sentence..
Quiz answers: 1 B, 2 C, 3 A, 4 B, 5 C, 6 A, 7 B, 8 C, 9 A, 10 B, 11 C, 12 A, Challenge 1 B, Challenge 2 C.
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Classify changes | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O2 Give evidence | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O3 Explain with particles | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O4 Predict outcomes | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
Courseversity badge thresholds (overall quiz score): Gold = 90–100%; Silver = 80–89.9%; Bronze = 70–79.9%. A badge is never a full record of progress.
If a learner struggles
- Find the misconception: “All changes can be undone.” Some cannot.
- Explain another way: use real objects, pictures or actions first, then words.
- Show a simpler example: Classify changes.
- Guided practice: work through one example together and let the learner try the next one.
- Reassess: use the quiz again or the worksheet.
- Move on when the learner shows Silver-level evidence independently.
For parents and guardians
In this lesson your child sorts changes. You do not need to be an expert to help.
- Talk about kitchen changes.
- Ask “Can we undo it?”
- Adult handles chemicals.
- Ask “how do you know?” after each answer, and listen.
- Praise effort, not only right answers. Mistakes are how we learn.
- Ten to fifteen minutes a day is better than one long session.
Teacher package
1–5. Objectives, prerequisites, materials, preparation, duration
Lesson objectives. Learners will: classify changes; give evidence; explain with particles; predict outcomes.
Prerequisite knowledge. Grade 4 ideas: properties of materials, states of matter, melting, freezing, evaporation, dissolving and reversible changes.
Materials. Cards, baking soda, vinegar (adult). Low-resource options: use chalk or charcoal on a board or wall, drawings in the sand, and objects from the classroom instead of printed materials.
Preparation. Print cards.
Suggested duration. 45–60 minutes. It can be split into two shorter sessions.
6–9. Teaching procedure, explanation notes, guided and independent activities
Introduction (5 min). Melt and burn paper pieces in pictures and ask, “Which can be undone?”
Explanation (10 min). Teach changes.
Guided activity (10 min). Learners sort.
Independent activity (10 min). Learners observe.
Assessment and reflection (5 min). Ask each learner to say one thing they learned and how they know it.
Key questions. Can we undo it? What is the evidence?
Teacher explanation notes. Start with real objects and safe, hands-on observation. Then talk about what was seen, then draw and write. Always say “how do you know?”. Keep to the safety notes, and use local, safe materials.
10–12. Differentiation, formative assessment, common misconceptions
Support. Use real objects and pictures, short sentences and a partner. Let learners point, show or draw instead of writing. Extension. Ask learners to find a new example at home and explain how they know.
Formative assessment. Listen to learners read and explain, ask “how do you know?”, and check the independent work.
Misconceptions. “All changes can be undone.” Some cannot.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz, the 10-mark exam practice and the worksheet on this page. All answers and marking guides are in the answer sections above. Re-check every answer before use.
16–19. Remediation, enrichment, homework, teacher reflection
Remediation. Classify changes. Enrichment. Look for one new example near your home or school, draw it and explain it to someone. Homework. See above.
Teacher reflection. After teaching, record: which ideas learners understood; which misconceptions occurred; which activities worked; which learners need more practice; and what to improve next time.
Sources and standards
This lesson is based on the sources below, and no official endorsement is claimed. Reference starting points: Next Generation Science Standards, Cambridge Primary Science and the IB Primary Years Programme. Where a standard code is named, it points to the official framework.
Research used to shape this lesson. Courseversity Science curriculum, Grade 5 Unit 4, topic 10; Next Generation Science Standards, structure and properties of matter; Cambridge Primary Science Stage 5, chemistry: states of matter and materials; IB Primary Years Programme, how the world works. These sources informed the lesson.