Lesson Plan: Physical and Chemical Changes

Learning Objectives

Students will:

✔ Identify physical and chemical changes.

✔ Observe changes through simple activities.

✔ Explain why some changes are reversible while others are irreversible.

✔ Describe rusting and its prevention.

✔ Develop scientific observation and reasoning skills.

Previous Knowledge (पूर्व ज्ञान)

Ask students:

  • What happens when ice melts?
  • Can melted ice become ice again?
  • What happens when paper burns?
  • Why do old iron gates become reddish-brown?

Expected Response: Some changes can be reversed, while others cannot.

Key Vocabulary

English

हिन्दी

Change

परिवर्तन

Physical Change

भौतिक परिवर्तन

Chemical Change

रासायनिक परिवर्तन

Reversible

प्रतिवर्ती

Irreversible

अप्रतिवर्ती

Rusting

जंग लगना

Melting

पिघलना

Freezing

जमना

Burning

जलना

Evaporation

वाष्पीकरण

Condensation

संघनन

Oxidation

ऑक्सीकरण

Introduction Activity (5–10 Minutes)

Teacher Activity

Show students:

  • An ice cube
  • A piece of paper
  • A rusty nail

Ask:

English

  • What happens when ice is left outside?
  • Can burnt paper become paper again?
  • Why does iron rust?

हिन्दी

  • बर्फ बाहर रखने पर क्या होता है?
  • क्या जला हुआ कागज़ फिर से कागज़ बन सकता है?
  • लोहे में जंग क्यों लगती है?

Lead students to the concept of Changes.

Study Material

What is a Change?

English

A change is any alteration in the shape, size, colour, state, or properties of a substance.

हिन्दी

किसी पदार्थ के आकार, रूप, रंग, अवस्था या गुणों में होने वाले परिवर्तन को परिवर्तन कहते हैं।

Physical Change (भौतिक परिवर्तन)

English

A physical change is a change in which no new substance is formed.

Usually, it is reversible.

Characteristics

  • No new substance is formed.
  • Only shape, size, or state changes.
  • Usually reversible.
  • Temporary in nature.

Examples

  • Melting of ice
  • Freezing of water
  • Dissolving sugar in water
  • Cutting paper
  • Stretching a rubber band

हिन्दी

भौतिक परिवर्तन वह परिवर्तन है जिसमें कोई नया पदार्थ नहीं बनता।

इसके अधिकांश परिवर्तन प्रतिवर्ती होते हैं।

उदाहरण

  • बर्फ का पिघलना
  • पानी का जमना
  • चीनी का पानी में घुलना
  • कागज़ काटना
  • रबर खींचना

Chemical Change (रासायनिक परिवर्तन)

English

A chemical change is a change in which one or more new substances are formed.

Usually, it is irreversible.

Characteristics

  • New substance is formed.
  • Permanent change.
  • Difficult to reverse.
  • Heat, light, gas, colour change, or precipitate may be produced.

Examples

  • Burning paper
  • Rusting of iron
  • Cooking food
  • Digestion of food
  • Curd formation from milk

हिन्दी

रासायनिक परिवर्तन वह परिवर्तन है जिसमें नया पदार्थ बनता है।

यह सामान्यतः अप्रतिवर्ती होता है।

उदाहरण

  • कागज़ जलना
  • लोहे में जंग लगना
  • भोजन पकाना
  • भोजन का पचना
  • दूध से दही बनना

Differences Between Physical and Chemical Changes

Physical Change

Chemical Change

No new substance is formed.

A new substance is formed.

Usually reversible.

Usually irreversible.

Temporary.

Permanent.

Only physical properties change.

Chemical properties change.

हिन्दी

भौतिक परिवर्तन

रासायनिक परिवर्तन

नया पदार्थ नहीं बनता।

नया पदार्थ बनता है।

सामान्यतः प्रतिवर्ती।

सामान्यतः अप्रतिवर्ती।

अस्थायी।

स्थायी।

Rusting of Iron (लोहे में जंग लगना)

English

Rusting is a chemical change.

Iron reacts with oxygen and moisture to form rust.

Conditions required:

  • Iron
  • Oxygen
  • Water (Moisture)

हिन्दी

लोहे में जंग लगना एक रासायनिक परिवर्तन है।

लोहा, ऑक्सीजन तथा नमी की उपस्थिति में अभिक्रिया करके जंग बनाता है।

Prevention of Rusting

English

  • Painting
  • Greasing
  • Oiling
  • Galvanization
  • Chrome plating

हिन्दी

  • पेंट करना
  • ग्रीस लगाना
  • तेल लगाना
  • गैल्वेनाइजेशन
  • क्रोम प्लेटिंग

Everyday Examples of Changes

Physical Change

Chemical Change

Ice melting

Burning wood

Water boiling

Cooking food

Cutting vegetables

Digestion

Folding clothes

Rusting

Breaking chalk

Milk to curd

Classroom Activities

Activity 1 – Ice Melting

Materials:

  • Ice cubes

Students observe:

  • Ice melts into water.
  • Water freezes back into ice.

Conclusion: Physical change.

Activity 2 – Dissolving Salt

Students dissolve salt in water.

Discuss how water can be evaporated to recover the salt.

Conclusion: Physical change.

Activity 3 – Vinegar and Baking Soda (Teacher Demonstration)

Mix vinegar and baking soda.

Students observe:

  • Bubbles (gas)
  • Temperature change

Conclusion: Chemical change because a new substance (carbon dioxide gas) is formed.

Activity 4 – Observe Rust

Show a rusty nail and a new nail.

Students compare colour and texture.

Discuss why rust forms and how it can be prevented.

Blackboard Summary

Changes ↓ Physical Change • No new substance • Usually reversible ↓ Chemical Change • New substance formed • Usually irreversible ↓ Rusting ↓ Prevention of Rusting

 

Assessment Questions

Oral Questions

  1. What is a physical change?
  2. Give two examples of chemical changes.
  3. What is rusting?
  4. Why is burning paper a chemical change?
  5. Name two methods to prevent rusting.

Multiple Choice Questions

1

Which of the following is a physical change?

A. Rusting

B. Burning paper

C. Melting ice ✔

D. Cooking food

2

Rusting takes place in the presence of

A. Oxygen and moisture ✔

B. Sunlight only

C. Carbon dioxide only

D. Nitrogen only

3

Cooking food is

A. Physical change

B. Chemical change ✔

C. No change

D. Mechanical change

4

Which process forms a new substance?

A. Cutting paper

B. Boiling water

C. Burning wood ✔

D. Melting wax

5

Painting iron prevents

A. Melting

B. Rusting ✔

C. Boiling

D. Freezing

Short Answer Questions

  1. Define physical and chemical changes.
  2. Give three examples of each.
  3. Write two differences between physical and chemical changes.
  4. Explain rusting.
  5. Write four methods of preventing rust.

HOTS Questions

  1. Why is melting wax considered a physical change, but burning wax a chemical change?
  2. Why do iron objects rust more quickly during the rainy season?
  3. Can one process involve both physical and chemical changes? Explain with an example (e.g., burning a candle: wax melts—physical change; wax burns—chemical change).

Worksheet

Fill in the Blanks

  1. Melting of ice is a __________ change.
  2. Rusting is a __________ change.
  3. Burning paper forms a __________ substance.
  4. Painting iron prevents __________.
  5. Cooking food is a __________ change.

Answers

  1. Physical
  2. Chemical
  3. New
  4. Rusting
  5. Chemical

Match the Following

A

B

Ice Melting

Physical Change

Rusting

Chemical Change

Painting

Prevents Rust

Burning Paper

New Substance

Freezing Water

Physical Change

Art Integration

  • Draw a comparison chart of physical and chemical changes.
  • Make a poster on "How to Prevent Rusting."
  • Prepare a collage using pictures of changes observed in daily life.

Life Skills Integration

Students learn to:

  • Protect iron tools and bicycles from rust.
  • Observe changes safely during experiments.
  • Handle chemicals responsibly.
  • Appreciate the importance of chemical changes in cooking, medicine, and industry.

Home Assignment

  1. Make a table of 10 physical changes and 10 chemical changes observed at home.
  2. Observe any iron object in your surroundings and note whether it has rust. Suggest one method to prevent rusting.
  3. Write five sentences in English and Hindi explaining the difference between physical and chemical changes.

Learning Check (Exit Ticket)

Before leaving the class, ask students:

  • What is a physical change?
    A change in which no new substance is formed. / वह परिवर्तन जिसमें कोई नया पदार्थ नहीं बनता।
  • Name one chemical change.
    Rusting of iron / लोहे में जंग लगना
  • Why is rusting a chemical change?
    Because a new substance (rust) is formed. / क्योंकि इसमें नया पदार्थ (जंग) बनता है।
  • Name two methods to prevent rusting.
    Painting and oiling. / पेंट करना और तेल लगाना।
  • Give one example of a reversible change.
    Melting and freezing of ice. / बर्फ का पिघलना और फिर जमना।