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CBSE Class 7 Science Chapter 5 Physical and Chemical Changes Worksheet with Answers

Physical and Chemical Changes is a foundational chapter in NCERT Class 7 Science that helps students understand matter transformations around them. This printable worksheet offers structured practice across multiple question formats—MCQs, fill-in-the-blanks, True/False, short and long answers—covering rusting, crystallisation, galvanisation and change types. Difficulty level: Medium. Suggested time: 60 minutes. Complete answer key included.

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Key takeaways

  • ✓Physical changes are reversible and do not form new substances; chemical changes create new substances with different properties
  • ✓Rusting of iron is a chemical change requiring oxygen and moisture, preventable through painting, oiling or galvanisation
  • ✓Crystallisation is a physical process used to purify salts and separate impurities from solutions
  • ✓Galvanisation is coating iron with zinc to prevent rusting, commonly used for buckets and pipes
  • ✓Burning of paper, cooking of food, and digestion are irreversible chemical changes producing new substances
  • ✓Melting, freezing, boiling and condensation are reversible physical changes without new substance formation
  • ✓Indicators like phenolphthalein and litmus help detect chemical changes by showing colour changes in reactions

Quick Chapter Recap – Physical and Chemical Changes

Before attempting the worksheet, revisit these core concepts from CBSE Class 7 Science Chapter 5. A physical change is a temporary, reversible change where no new substance forms—only the state, shape or size alters. Examples include melting of ice, dissolving sugar in water, and tearing paper. The chemical composition remains identical. A chemical change is permanent and irreversible, producing one or more new substances with entirely different properties. During chemical changes, energy (heat, light or sound) is often absorbed or released. Common indicators include colour change, gas evolution, temperature change or precipitate formation. Rusting of iron is a slow chemical change needing oxygen and water, forming reddish-brown iron oxide. Crystallisation is the physical process of obtaining pure crystals from a saturated solution by slow evaporation, widely used in salt purification. Galvanisation involves coating iron or steel with a thin layer of zinc to prevent rusting, extending the life of pipes, gates and buckets.
  • Physical change: reversible, no new substance, e.g. ice melting, dissolving salt
  • Chemical change: irreversible, new substance formed, e.g. burning magnesium ribbon, rusting
  • Rusting requires both oxygen and moisture; prevented by painting, oiling or galvanisation
  • Crystallisation purifies substances like common salt from impure solutions
  • Galvanisation is the zinc-coating process protecting iron from corrosion

Section A – Multiple Choice Questions (MCQs)

This section contains 6 multiple-choice questions testing your understanding of key concepts in Physical and Chemical Changes. Each question has four options; choose the most appropriate answer. These MCQs mirror the pattern seen in CBSE term exams and NCERT Class 7 Science assessments. Topics include identification of physical versus chemical changes, rusting conditions, crystallisation steps, and galvanisation purpose. Carefully read each statement before selecting your answer. Answers with explanations are provided in the complete answer key section at the end of this worksheet.
  • Q1. Which of the following is a chemical change? (a) Melting of ice (b) Rusting of iron (c) Dissolving sugar in water (d) Breaking of glass
  • Q2. Galvanisation is the process of coating iron with: (a) Copper (b) Zinc (c) Silver (d) Aluminium
  • Q3. Crystallisation is used to purify: (a) Petrol (b) Common salt (c) Oxygen (d) Milk
  • Q4. Rusting of iron requires the presence of: (a) Only oxygen (b) Only water (c) Both oxygen and moisture (d) Carbon dioxide
  • Q5. Which indicator turns pink in a base? (a) Methyl orange (b) Litmus (c) Phenolphthalein (d) Turmeric
  • Q6. Which change is reversible? (a) Burning of candle (b) Cooking of egg (c) Freezing of water (d) Digestion of food

Section B – Fill in the Blanks

Complete each sentence by filling the blank with the correct word or phrase from the chapter on Physical and Chemical Changes. This section tests your recall of NCERT Class 7 Science definitions, processes and examples. Pay attention to the exact terminology used in the NCERT textbook—terms like crystallisation, galvanisation, rusting, reversible and irreversible are key. Write your answers clearly. The complete answer key at the end provides the correct words with brief context to help you cross-check and learn.
  • Q7. The process of coating iron with zinc to prevent rusting is called __________.
  • Q8. __________ is a chemical change in which iron reacts with oxygen and moisture to form iron oxide.
  • Q9. Changes that can be reversed are called __________ changes.
  • Q10. The process of obtaining crystals from a saturated solution is known as __________.
  • Q11. Burning of magnesium ribbon produces a __________ flame and forms magnesium oxide.
  • Q12. When carbon dioxide is passed through lime water, it turns __________.

Section C – True or False Statements

Read each statement carefully and write 'True' if the statement is correct or 'False' if it is incorrect. These statements cover distinctions between physical and chemical changes, properties of rusting, crystallisation applications, and examples from everyday life. In Class 7 Science notes and CBSE exams, True/False questions test your conceptual clarity and attention to detail. After completing, refer to the answer key where each answer is justified with a one-line explanation rooted in NCERT principles.
  • Q13. Melting of butter is a chemical change.
  • Q14. Digestion of food in our body is a chemical change.
  • Q15. Rusting can be prevented by applying a coat of paint on iron articles.
  • Q16. Crystallisation is a chemical change.
  • Q17. Formation of curd from milk is a physical change.
  • Q18. Galvanised iron pipes are coated with a layer of zinc.

Section D – Short Answer Questions (2–3 marks each)

Answer the following questions in 30–50 words each. These short-answer questions require you to explain concepts, give examples or describe processes studied in CBSE Class 7 Science Chapter 5. Focus on clarity and use correct scientific terminology from the NCERT textbook—mention rusting, crystallisation, galvanisation where relevant. Marks are awarded for accurate content and clear expression. Model answers are provided in the answer key to help you frame ideal responses for term exams.
  • Q19. Differentiate between physical and chemical changes with one example each.
  • Q20. What is rusting? Write two conditions necessary for rusting to occur.
  • Q21. Explain the process of crystallisation. Give one use of this process.
  • Q22. What is galvanisation? Why is it done?
  • Q23. List three indicators of a chemical change.

Section E – Long Answer and HOTS Questions (3–5 marks each)

These three questions demand detailed explanations, application of concepts and higher-order thinking skills (HOTS). Each answer should be 80–100 words. Demonstrate your understanding of the principles behind rusting, crystallisation and change classification. Use diagrams or flowcharts if helpful. Examiners look for logical flow, examples and correct use of NCERT Class 7 Science vocabulary. The answer key provides comprehensive model answers showing depth and structure expected in CBSE term exams.
  • Q24. Describe three methods to prevent rusting of iron. Explain how each method works.
  • Q25. Explain the process of crystallisation step-by-step with the help of an example. Why is it considered a physical change?
  • Q26. A student observes the following changes: (i) Dissolving salt in water (ii) Burning a candle (iii) Boiling water (iv) Ripening of fruits. Classify each as physical or chemical change and justify your classification.

Section F – Case-Study Based Question

Read the case study carefully and answer the sub-questions that follow. Case-study questions are now a regular feature in CBSE Class 7 Science exams, testing your ability to apply chapter concepts to real-life scenarios. This question integrates multiple topics from Physical and Chemical Changes—rusting, prevention methods, reversibility and environmental factors. Answer in clear, concise sentences. The answer key provides detailed solutions for each sub-part.

Complete Answer Key with Explanations

Below are the answers to all questions in this CBSE Class 7 Science Chapter 5 worksheet. Each answer includes a brief explanation to reinforce your understanding. Cross-check your responses, identify mistakes and revise concepts accordingly. For deeper practice and instant doubt-solving with photo-upload, students can explore CBSETUTOR.ai—a 24×7 AI tutor available at a flat ₹999/month for all classes 6–12, with a 3-day free trial. Consistent worksheet practice alongside AI-powered guidance builds strong fundamentals and exam confidence.
  • A1. (b) Rusting of iron – It is a chemical change where iron oxide (a new substance) is formed.
  • A2. (b) Zinc – Galvanisation coats iron with zinc to prevent contact with moisture and oxygen.
  • A3. (b) Common salt – Crystallisation purifies salts by separating dissolved impurities.
  • A4. (c) Both oxygen and moisture – Rusting is an oxidation reaction requiring both.
  • A5. (c) Phenolphthalein – It turns pink in basic solutions, a sign of chemical change detection.
  • A6. (c) Freezing of water – Water can melt back to liquid; it is a reversible physical change.
  • A7. galvanisation
  • A8. Rusting
  • A9. reversible / physical
  • A10. crystallisation
  • A11. brilliant white / dazzling white
  • A12. milky / turbid
  • A13. False – Melting is a physical change; butter remains butter, only state changes.
  • A14. True – Digestion breaks food into new substances, a chemical change.
  • A15. True – Paint prevents contact of iron with air and moisture, stopping rusting.
  • A16. False – Crystallisation is a physical process; no new substance forms.
  • A17. False – Curdling of milk is a chemical change forming lactic acid and new substances.
  • A18. True – Galvanisation involves coating iron with zinc.
  • A19. Physical changes are reversible and no new substance is formed, e.g. melting of ice. Chemical changes are irreversible and new substances with different properties are formed, e.g. burning of paper.
  • A20. Rusting is a chemical change where iron reacts with oxygen and moisture to form reddish-brown iron oxide. Two necessary conditions: (i) presence of oxygen (air), (ii) presence of water or moisture.
  • A21. Crystallisation is the process of obtaining pure crystals from a saturated solution by slow evaporation. For example, common salt is purified by dissolving it in water, filtering impurities, and evaporating water slowly to obtain salt crystals. Use: purification of salts.
  • A22. Galvanisation is the process of coating iron or steel articles with a thin layer of zinc to prevent rusting. It is done to protect iron from corrosion by preventing contact with oxygen and moisture, extending the life of articles like pipes and buckets.
  • A23. Three indicators: (i) Change in colour, (ii) Evolution of gas (bubbles), (iii) Change in temperature (heat or light release).
  • A24. Three methods: (i) Painting – A layer of paint prevents oxygen and moisture from reaching iron surface. (ii) Oiling or greasing – Oil forms a protective layer blocking air and water. (iii) Galvanisation – Coating with zinc prevents direct contact with corrosive agents. Each method acts as a barrier between iron and the environment.
  • A25. Crystallisation steps: (i) Prepare a saturated solution of the substance (e.g. salt in water). (ii) Filter to remove insoluble impurities. (iii) Heat the solution to evaporate some water. (iv) Cool slowly; pure crystals form and settle. (v) Separate crystals by filtration and dry. It is a physical change because the chemical composition of salt remains unchanged, only the physical state changes from dissolved to solid crystals.
  • A26. (i) Dissolving salt – Physical change; salt can be recovered by evaporation, no new substance. (ii) Burning candle – Chemical change; wax burns to form carbon dioxide, water vapour and heat, irreversible. (iii) Boiling water – Physical change; water vapour can condense back to liquid, reversible. (iv) Ripening of fruits – Chemical change; complex sugars and acids form, irreversible, cannot turn ripe fruit unripe.
  • Case Study Answers: (a) Rusting is the chemical process where iron reacts with oxygen and moisture to form iron oxide (rust). Two essential conditions: oxygen (from air) and water/moisture. (b) Painting prevents rusting by forming a protective layer that stops oxygen and moisture from coming in contact with the iron surface. (c) Galvanisation is coating iron with a layer of zinc to prevent rusting. Example: galvanised iron buckets, water pipes or fencing wire.

How to Use This Worksheet Effectively for CBSE Exams

Worksheets are powerful revision tools when used strategically. First, read NCERT Class 7 Science Chapter 5 thoroughly and make brief notes on physical and chemical changes, rusting, crystallisation and galvanisation. Next, attempt this worksheet in one 60-minute sitting without referring to notes—simulate exam conditions. Mark your answers, then use the answer key to evaluate and identify weak areas. Revisit those topics in the textbook or Class 7 Science notes. Repeat the worksheet after a week to track improvement. For students struggling with specific concepts or needing step-by-step problem solving, CBSETUTOR.ai offers an AI tutor that answers doubts instantly via photo upload, provides chapter summaries and generates unlimited practice questions—all at ₹999/month across classes 6–12 with a 3-day free trial. Combining printed worksheets with AI-driven personalised support builds both speed and accuracy for term exams.
  • Attempt the worksheet in one 60-minute session under exam-like conditions
  • Self-evaluate using the detailed answer key and note mistakes
  • Revise weak topics from NCERT textbook or reliable Class 7 Science solutions
  • Re-attempt the worksheet after one week to measure retention and improvement
  • Use CBSETUTOR.ai for instant doubt-solving, chapter summaries and endless practice at ₹999/month

Common Mistakes Students Make in Physical and Chemical Changes

Many Class 7 students confuse reversible with irreversible changes. Remember: if you can get the original substance back easily, it is physical (e.g. melting ice). If a completely new substance forms that cannot revert, it is chemical (e.g. burnt paper to ash). Another error is assuming all colour changes are chemical—dissolving coloured crystals in water is physical, but a metal turning black when heated (oxidation) is chemical. Students often forget that rusting needs both oxygen and water; one alone will not cause rust. In crystallisation questions, some write it as a chemical change—it is purely physical because the salt's chemical formula does not change. During galvanisation questions, mentioning 'iron coating' instead of 'zinc coating' loses marks. Always use exact NCERT terminology. Finally, in long answers, students list points without explanation—always justify with a reason or example to score full marks in CBSE exams.
  • Confusing reversible (physical) with irreversible (chemical) changes
  • Assuming every colour change is a chemical reaction; context matters
  • Forgetting that rusting requires both oxygen and moisture, not just one
  • Writing crystallisation as a chemical change instead of physical process
  • Stating 'iron coating' in galvanisation instead of the correct 'zinc coating'
  • Listing points without justification or examples in descriptive answers

Additional Practice Resources and Support

Beyond this worksheet, CBSE Class 7 students should solve NCERT in-text and end-of-chapter questions, refer to NCERT Exemplar for higher-order problems, and practice previous years' term exam papers. Many schools provide Class 7 Science notes and sample papers—use them for variety. Online platforms like CBSETUTOR.ai complement printed resources by offering a 24×7 AI tutor that solves doubts via photo upload, generates custom worksheets for weak chapters, and explains each step in student-friendly language. At a flat ₹999/month for classes 6–12 with a 3-day free trial, it is an affordable alternative to expensive tuition. Regular worksheet practice, combined with immediate AI feedback, accelerates mastery of Physical and Chemical Changes and builds confidence for scoring high in Science exams.
  • Solve all NCERT in-text and end-of-chapter exercises for Chapter 5
  • Attempt NCERT Exemplar problems for advanced practice and HOTS questions
  • Review previous years' CBSE Class 7 term exam papers for question patterns
  • Use school-provided Class 7 Science notes and sample papers for variety
  • Try CBSETUTOR.ai for instant doubt-solving, custom worksheets and 24×7 AI tutor support at ₹999/month

Frequently asked questions

What is the difference between physical and chemical changes in Class 7 Science Chapter 5?+
Physical changes are reversible, no new substance forms, and only state or appearance alters (e.g. melting ice). Chemical changes are irreversible, produce new substances with different properties, and often release energy (e.g. burning wood). NCERT Class 7 Science emphasises this distinction throughout Chapter 5.
What are the two essential conditions required for rusting of iron?+
Rusting requires both oxygen (from air) and moisture (water). Without either, rusting does not occur. This is why iron articles stored in dry conditions or coated with paint, oil or zinc (galvanisation) resist rust formation, as per CBSE Class 7 Science Chapter 5.
What is crystallisation and why is it considered a physical change?+
Crystallisation is the process of obtaining pure solid crystals from a saturated solution by slow evaporation. It is a physical change because the chemical composition of the substance remains the same; only the physical state changes from dissolved to crystalline solid. It is commonly used to purify common salt.
What is galvanisation and give one example of a galvanised article?+
Galvanisation is coating iron or steel with a thin layer of zinc to prevent rusting. The zinc layer acts as a barrier, blocking contact with oxygen and moisture. Common examples include galvanised iron buckets, water pipes, fencing wire and roofing sheets.
How can rusting of iron be prevented? List three methods.+
Three methods: (1) Painting – forms a protective layer preventing air and moisture contact. (2) Oiling or greasing – blocks oxygen and water. (3) Galvanisation – zinc coating protects the iron surface. All methods create a barrier between iron and environmental factors causing rust.
Is digestion of food a physical or chemical change? Why?+
Digestion is a chemical change because food is broken down into simpler molecules like glucose, amino acids and fatty acids, which are entirely new substances. The process is irreversible—you cannot convert digested food back into the original meal.
What indicators show that a chemical change has occurred?+
Key indicators include: (1) Change in colour, (2) Evolution of gas (bubbles), (3) Change in temperature (heat or light), (4) Formation of precipitate. For example, when vinegar reacts with baking soda, bubbles (CO₂ gas) form, indicating a chemical change.
Why is burning of a candle considered a chemical change?+
When a candle burns, wax reacts with oxygen to form carbon dioxide, water vapour, heat and light. These are new substances with properties different from wax. The change is irreversible—you cannot get the original wax back from the products.
Can physical changes be reversed? Give an example.+
Yes, physical changes are generally reversible. For example, when ice melts to water (physical change), you can freeze it again to get ice. Similarly, dissolving salt in water is reversible by evaporation. No new substance is formed in these processes.
Where can I get more worksheets and instant doubt-solving for CBSE Class 7 Science?+
CBSETUTOR.ai provides unlimited worksheets, chapter-wise practice questions and a 24×7 AI tutor that solves doubts via photo upload. It covers all chapters of Class 7 Science with step-by-step explanations at ₹999/month for classes 6–12, with a 3-day free trial to explore features.

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