Introduction
In Class 9 Science, one of the most important and easy-to-understand topics is the difference between physical and chemical change. These changes happen all around us—when ice melts, or when paper burns. But how do we know which one is physical and which one is chemical?
In this article, we will explain this topic in very simple language, with daily life examples, a comparison table, and key points to help you learn better. Whether you’re preparing for your exam or just curious, this guide will make things crystal clear!
What Does Change Mean in Science?
Change, as used in science, is the state in which something changes from its previous state. It can happen in the way something looks, feels, or behaves. There are two main types of changes:
- Physical Change
- Chemical Change
Let’s explore what these two changes mean and how to easily tell them apart.
What is a Physical Change?
A physical change is a type of change in which the appearance, shape, size, or state of a substance changes, but the actual substance remains the same.
Examples of Physical Change
- Ice melting into water
- Boiling water
- Tearing a paper
- Dissolving sugar in water
- Breaking glass
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Main Characteristics of Physical Change
- No new substance is created.
- Usually reversible (can go back to original form).
- Changes only physical properties like shape or state.
- No major energy (like heat or light) is released.
Example: If you melt ice, it becomes water. However, it is still H₂O; the only thing that has changed is the shape. That’s a physical change.
What is a chemical change?
A substance undergoes a chemical transformation when it changes into something entirely different. It changes both physically and chemically. These changes are usually not reversible.
Examples of Chemical Change
- Burning paper
- Rusting of iron
- Cooking an egg
- Making curd from milk
- Digesting food
Main Characteristics of Chemical Change
- A new substance is formed.
- Usually irreversible.
- Original chemical nature changes.
- Often heat, light, or gas is released.
Example: When wood burns, it turns into ash and smoke. A new substance is formed. You can’t get the wood back again. That’s a chemical change.
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Comparison Table: Physical Change vs Chemical Change
| Feature | Physical Change | Chemical Change |
|---|---|---|
| New Substance Formed? | ❌ No | ✅ Yes |
| Reversible? | ✅ Often reversible | ❌ Usually irreversible |
| Change in Physical Properties? | ✅ Yes | ✅ Yes |
| Change in Chemical Properties? | ❌ No | ✅ Yes |
| Energy Involved? | ❌ Little or none | ✅ Often involves heat or light |
| Common Example | Melting ice | Burning paper |
This table will help you remember the difference between physical and chemical change quickly and easily.
How to Identify a Physical Change?
Look for these clues:
- Change in shape, size, or state (like melting, cutting)
- No new smell or color appears
- The material can return to its original form
- No gas, heat, or light is produced
Example: Crushing a plastic bottle – It’s still plastic, just a different shape.
How to Identify a Chemical Change?
Here are signs of a chemical change:
- A new smell or gas comes out
- Color changes permanently
- A precipitate is a solid that can form in a liquid.
- Heat, light, or sound is given off
- The original material is gone
Example: Frying an egg – The egg white becomes solid and changes color. It’s not reversible. That’s chemical!
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Real-Life Examples
Understanding the difference between physical and chemical change becomes easier when we relate it to real life.
Physical Change in Daily Life
- Melting butter
- Sharpening a pencil
- Freezing juice
- Folding clothes
- Breaking a mirror
Chemical Change in Daily Life
- Baking a cake
- Burning incense
- Iron rusting in the rain
- Spoiling milk
- Lighting a matchstick
When you look around, you’ll find many such examples happening every day!
Simple Activities for Better Understanding
Activity 1: Physical Change
Things needed: Ice cube, bowl
Steps:
- Place an ice cube in a bowl.
- Let it melt naturally.
- Observe the water formed.
Conclusion: The ice changed its state, but it’s still water. No new substance. It’s a physical change.
Activity 2: Chemical Change
Things needed: Paper, candle (Adult supervision required)
Steps:
- Light a candle.
- Hold a piece of paper above the flame.
- Observe as the paper burns.
Conclusion: The paper turns into ash and cannot be changed back. A new substance (ash, smoke) is created. It’s a chemical change.
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Why It’s Important to Learn This?
Learning the difference between physical and chemical change is useful for:
✅ Understanding how the world around you works
✅ Performing safe experiments in labs
✅ Scoring better in science exams
✅ Making smart observations in daily life
✅ Building strong scientific thinking
Quiz Time: Test What You Learned
- Is boiling milk a physical or chemical change?
✅ Chemical - Tearing paper – Physical or Chemical?
✅ Physical - Burning a candle – Which type of change?
✅ Chemical - Melting gold – What kind of change?
✅ Physical - Is rusting of iron reversible?
❌ No – It’s a chemical change
Tips to Remember the Difference Easily
- If no new substance is formed, it’s a physical change.
- A chemical change occurs when a new substance is created and the old one is destroyed.
- Physical = can often reverse.
- Chemical = permanent and creates something new.
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Conclusion
Now you know the clear and simple difference between physical and chemical change. Physical changes are like changing clothes—your look changes, but you are still you. You can never get the batter back after a chemical shift, just like when you bake a cake!
By observing simple things around you, you can now easily tell if a change is physical or chemical. Keep practicing, stay curious, and science will always be fun!https://allen.in/science/physical-and-chemical-changes-of-materials
