ICSE Class 8 Chemistry Physical and Chemical Changes Notes | PDF Download

Table of Contents

Physical and Chemical changes | ICSE Class 8 Chemistry Notes

Physical and Chemical Changes is one of the most important chapters in ICSE Class 8 Chemistry. This chapter helps students understand how substances change and whether new substances are formed during the process. Students often get questions in examinations based on definitions, examples, differences, and applications of these changes.
In this article, you will get ICSE Class 8 Chemistry Physical and Chemical Changes Notes PDF, important definitions, examples, differences, and revision points for better exam preparation.

Study Support by Rohit Academy

Rohit Academy offers expert-curated ICSE Class 8 Chemistry Study Materials including ICSE Physical and Chemical Changes Chapter Notes, diagrams, and key formulas for better understanding.

You can also visit:

☛ ICSE Class 8 Chemistry Chapter 2: Physical and Chemical Changes Selina Solutions

☛ ICSE Class 8 Physics

☛ ICSE Class 8 Chemistry

☛ ICSE Class 8 Mathematics

☛ ICSE Class 8 Biology

Physical and Chemical Changes Notes ICSE Class 8 Chemistry

Introduction

Change is a universal phenomenon. It can be natural or man-made, slow or fast, and temporary or permanent. To understand these changes, we classify them into specific categories.Classification of Changes

Classification of Changes

Type of Change	Description	Examples
Slow Change	Takes a long time (hours, days, or years) to complete	Rusting of iron Formation of curd from milk Change of seasons Growth of a child into an adult Formation of fossil fuels
Fast Change	Occurs in a very short interval of time	Bursting of a cracker Lighting of an electric bulb Switching on a fan Blinking of eyes Cutting an apple
Natural Change	Occurs in nature by itself	Change of day and night Growth of trees Earthquakes Volcanic eruptions
Man-made Change	Occurs due to human effort or activities	Cooking of food Formation of steel from iron Making brass from copper and zinc Making jewellery from gold
Periodic Change	Repeated at regular intervals of time	Change of day and night Change of seasons
Non-periodic Change	Do not repeat at regular intervals	Earthquakes Landslides Epidemics A person becoming sick
Reversible Change	Changes can be reversed to obtain the original substance.	Water freezing into ice Ice melting into water
Irreversible Change	Changes cannot be reversed to get the original substance	Burning of paper Cooking of food Formation of curd from milk

Physical Change

A physical change is a temporary change in which no new substance is formed, and the chemical composition of the original substance remains the same. Only physical properties like state, shape, size, or colour may change.

Characteristics of a Physical Change

1. No New Substance is Formed:
Example:
When ice is taken out of a refrigerator, it melts into water. If the water is placed back in the refrigerator, it freezes again into ice. Both ice and water have the same chemical composition (H₂O).

2. The Change is Temporary and Reversible:
Example:
Ice melts into water and freezes again on cooling.
(Note: Some physical changes like tearing paper are irreversible but still physical because no new substance is created.)

3. No Change in Mass:

Example:
If wax is melted and then solidified again, the mass before and after the change remains identical.

4. No Gain or Loss of Energy

Usually, there is no significant gain or loss of energy.

Examples of Physical Changes

Melting of ice
Boiling of water
Formation of dew
Formation of clouds
Melting of wax
Sublimation of camphor
Magnetisation of iron
Breaking of glass
Drying of wet clothes
Crystallisation of salt or sugar
Dissolution of sugar in water
Glowing of an electric bulb
Manufacture of salt from sea water

Chemical Change

A chemical change is a permanent change in which new substances are formed with entirely different chemical compositions and properties compared to the original substance.

Characteristics of a Chemical Change

1. New Substances are Formed:
In a chemical change, new substances with different properties are produced.
Example:
When iron powder and sulphur powder are heated, a grey-black solid called iron sulphide (FeS) is formed.
Reaction: Fe + S → FeS
Iron sulphide has properties different from iron and sulphur.

2. The Change is Permanent and Irreversible:
Chemical changes are permanent and cannot be reversed easily.
Example:
When paper burns, it forms ash which cannot be changed back into paper.

3. There is Usually a Change in Mass:
In many chemical changes, the mass of the substance may change due to combination with another substance.
Example:
When magnesium is burned in air, it combines with oxygen to form magnesium oxide.
Reaction: 2Mg + O₂ → 2MgO
The final mass becomes greater because oxygen combines with magnesium.

4. Exchange of Energy Takes Place:
Chemical changes involve the release or absorption of energy.

Exothermic Reaction: Energy is released.

Endothermic Reaction: Energy is absorbed.

Example:
Burning of wood releases heat and light energy.

Examples of Chemical Changes

Cooking of rice
Formation of curd from milk
Digestion of food
Burning of fuel
Rusting of iron
Rotting of eggs

Special Case: Burning of a Candle

The burning of a candle involves both physical and chemical changes.

Physical Change : Wax melts from solid to liquid and solidifies again when cooled.

Chemical Change : Burning wax produces carbon dioxide and water vapour along with heat and light.

Differences Between Physical and Chemical Changes

Physical Change	Chemical Change
No new substance is formed	New substance is formed
Chemical composition remains the same	Chemical composition changes
Temporary and reversible	Permanent and irreversible
No change in mass	Usually change in mass
Original substance can be obtained back easily	Original substance cannot be obtained easily

ICSE Class 8 Chemistry Physical and Chemical Changes Notes PDF Download

Download the ICSE Class 8 Chemistry Physical and Chemical Changes Notes PDF and revise the chapter regularly for better results.

Conclusion

The chapter Physical and Chemical Changes forms the foundation of Chemistry in ICSE Class 8. Understanding the differences between physical and chemical changes, reversible and irreversible changes, and examples from daily life helps students score better in exams.