Introduction
Everything around us changes continuously. Some changes are temporary while others create completely new substances. In this chapter, students learn about physical changes, chemical changes, rusting, reversible and irreversible changes along with practical daily life examples.
What is a Physical Change?
A change in which no new substance is formed and the change is usually reversible is called a physical change.
Characteristics of Physical Changes
- No new substance is formed
- Usually temporary
- Often reversible
- Only shape or size changes
Examples of Physical Changes
- Melting of ice
- Boiling water
- Breaking glass
- Dissolving sugar in water
What is a Chemical Change?
A change in which a new substance is formed and the change is usually irreversible is called a chemical change.
Characteristics of Chemical Changes
- New substance is formed
- Usually permanent
- Often irreversible
- Heat, light or gas may be produced
Examples of Chemical Changes
- Burning paper
- Rusting of iron
- Cooking food
- Curd formation
Difference Between Physical and Chemical Change
| Physical Change | Chemical Change |
| No new substance formed | New substance formed |
| Usually reversible | Usually irreversible |
| Temporary | Permanent |
| Only physical properties change | Chemical properties change |
Rusting of Iron
What is Rusting?
Formation of reddish-brown rust on iron due to air and moisture is called rusting.
Conditions Needed for Rusting
Methods to Prevent Rusting
- Painting
- Oiling
- Greasing
- Galvanization
Slow and Fast Changes
Slow Changes
- Growth of tree
- Rusting of iron
Fast Changes
- Burning paper
- Bursting crackers
Reversible and Irreversible Changes
Reversible Changes
Changes that can be reversed back to the original form.
Example: Ice changing into water and again becoming ice.
Irreversible Changes
Changes that cannot be reversed.
Example: Burning wood.
Periodic and Non-Periodic Changes
Periodic Changes
Non-Periodic Changes
Expansion and Contraction
Expansion
Increase in size on heating is called expansion.
Contraction
Decrease in size on cooling is called contraction.
Important Terms
| Term | Meaning |
| Physical Change | No new substance formed |
| Chemical Change | New substance formed |
| Rusting | Formation of rust on iron |
| Expansion | Increase in size |
| Contraction | Decrease in size |
Quick Revision
- Physical changes are usually reversible.
- Chemical changes form new substances.
- Rusting requires air and moisture.
- Burning is a chemical change.
- Melting is a physical change.
Short Questions
- Define physical change.
- Define chemical change.
- Give two examples of physical changes.
- What is rusting?
- Name two methods to prevent rusting.
- Differentiate reversible and irreversible changes.
- Why is burning paper a chemical change?
Fill in the Blanks
- Rusting needs air and ______.
- Melting ice is a ______ change.
- Burning paper is a ______ change.
- Increase in size on heating is called ______.
Answers
- Moisture
- Physical
- Chemical
- Expansion
Activity – Rusting Experiment
Materials Needed
- Iron nail
- Water
- Test tube
Observation
After some days, reddish-brown rust appears on the nail.
Conclusion
Iron rusts in the presence of air and moisture.
Latest Updates – 2026
Updated: May 18, 2026
- ICSE schools are focusing more on practical Chemistry experiments.
- Concept-based questions are increasingly asked in exams.
- Students are encouraged to understand real-life examples of chemical changes.
- Rusting and reversible changes are important exam topics.
FAQ Section
What is a physical change?
A physical change is a change in which no new substance is formed.
What is a chemical change?
A chemical change forms a completely new substance.
What causes rusting?
Rusting occurs due to oxygen and moisture.
Is melting ice a physical change?
Yes, because no new substance is formed.
Why is burning paper irreversible?
Because ash and smoke cannot be converted back into paper.