NCERT Class 8 Science Science: Chapter 4 — Combustion and Flame
This chapter, "Combustion and Flame," from NCERT Class 8 Science, introduces the concept of combustion as a chemical process where a substance reacts with oxygen to produce heat. It defines combustible substances, also known as fuels, which can be solid, liquid, or gas. The chapter explores everyday fuels like wood, coal, petrol, and CNG, contrasting the burning of a candle with a flame versus coal without one. Through activities, it demonstrates that air is essential for combustion, showing how a flame is affected by air supply. The text also briefly touches upon the biological process of food breakdown in the body, comparing it to fuel combustion. This foundational understanding of combustion is crucial for comprehending various phenomena and technologies in science.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 8 |
| Subject | Science |
| Book | Science |
| Chapter | Chapter 4 — Combustion and Flame |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 635 |
Learning outcomes
- Define combustion and identify combustible substances (fuels).
- Differentiate between burning with and without a flame.
- Understand that air is necessary for combustion.
- Recognize different types of fuels used in daily life.
Vocabulary
| Word | Meaning |
|---|---|
| Combustion | A chemical process in which a substance reacts with oxygen to give off heat. |
| Fuel | The substance that undergoes combustion. |
| Combustible | A substance that undergoes combustion. |
| Flame | Visible, gaseous part of a fire. |
| Non-combustible | A substance that does not undergo combustion. |
| CNG | Compressed Natural Gas, a fuel. |
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Practice questions
- What is combustion? Answer: Combustion is a chemical process in which a substance reacts with oxygen to give off heat.
- What is a fuel? Answer: A fuel is a substance that undergoes combustion.
- Name three types of fuels. Answer: Solid, liquid, or gas fuels (e.g., wood, petrol, CNG).
- What is needed for combustion to take place? Answer: A combustible substance and oxygen (from air) are needed for combustion.
Frequently asked questions
What is combustion?
Combustion is a chemical process where a substance reacts with oxygen, releasing heat.
What is a fuel?
A fuel is a substance that undergoes combustion, providing heat.
Can you give examples of fuels?
Yes, examples include cowdung, wood, coal, petrol, diesel, and CNG.
Does combustion always produce a flame?
No, some substances like coal burn without a flame, while others like a candle burn with a flame.
Is air necessary for burning?
Yes, experiments show that air is essential for combustion to occur.
What happens if air supply is limited during burning?
If air supply is limited, the flame may flicker, produce smoke, or eventually go off.
Related resources
Important topics
Topics covered
NCERT Class 8 Science — Science — Chapter 4 — Combustion and Flame. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.