COMBUSTION AND FLAME | Class 8 Science Notes
By ConceptScroll Team · Published on 17 July 2026 · 3 min read
COMBUSTION AND FLAME – this guide gives you a concise, exam-ready overview of COMBUSTION AND FLAME from Class 8 Science, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
Types of Combustion
Combustion can be classified based on the speed and nature of the burning process. Rapid combustion is the fast burning of a substance producing heat and light, such as the burning of gas on a stove. Spontaneous combustion occurs when a material catches fire suddenly without an apparent external cause, like phosphorus burning in air at room temperature or coal dust igniting in mines. Forest fires can sometimes result from spontaneous combustion due to heat from the sun or lightning strikes, but most are caused by human carelessness. Explosions are violent combustion reactions releasing heat, light, sound, and gases rapidly, as seen in fireworks or when pressure is applied to crackers. Understanding these types helps in managing fire hazards and safety.
📊 Diagram: Fig. 4.8: Colours of a candle flame and the flame of a kitchen stove
🔗 Connection: This section introduces flames, their types, and structure, building on combustion types.
Frequently asked questions
1. List conditions under which combustion can take place.
Combustion can take place only when the following conditions are met: 1. Presence of a fuel. 2. Presence of oxygen (or air). 3. The fuel must be heated to its ignition temperature. 4. The fuel must be in a combustible state (usually gaseous or vapor form). If any of these conditions is missing, combustion will not occur.
2. Fill in the blanks. (a) Burning of wood and coal causes __________ of air. (b) A liquid fuel, used in homes is __________. (c) Fuel must be heated to its __________ __________ before it starts burning. (d) Fire produced by oil cannot be controlled by __________.
(a) Burning of wood and coal causes pollution of air. (b) A liquid fuel, used in homes is kerosene. (c) Fuel must be heated to its ignition temperature before it starts burning. (d) Fire produced by oil cannot be controlled by water.
3. Explain how the use of CNG in automobiles has reduced pollution in our cities.
CNG (Compressed Natural Gas) is a cleaner fuel compared to petrol and diesel. When used in automobiles, CNG burns more completely and produces fewer harmful emissions such as carbon monoxide, hydrocarbons, and particulate matter. It emits less carbon dioxide, which helps reduce air pollution and smog in cities. Hence, the use of CNG in vehicles has contributed to improved air quality and reduced health hazards caused by vehicle emissions.
4. Compare LPG and wood as fuels.
Comparison between LPG and wood as fuels:
| Aspect | LPG (Liquefied Petroleum Gas) | Wood |
|---|---|---|
| State | Gas (stored as liquid under pressure) | Solid |
| Cleanliness | Burns cleanly with little smoke | Produces smoke and ash |
| Energy content | High calorific value | Lower calorific value |
| Convenience | Easy to
Ready to ace this chapter?
Get the full COMBUSTION AND FLAME chapter — interactive notes, diagrams, worked solutions, polls and a free practice quiz — in the ConceptScroll app.
Study smarter with ConceptScroll
Daily NCERT-aligned reels, AI doubt solving and chapter quizzes — all free.
Start learning freeContinue reading
- LIGHT | Class 8 Science Notes
Clear NCERT-aligned notes on LIGHT for Class 8 Science.
- LIGHT | Class 8 Science Notes
Clear NCERT-aligned notes on LIGHT for Class 8 Science.
- LIGHT | Class 8 Science Notes
Clear NCERT-aligned notes on LIGHT for Class 8 Science.