Class 8 Exam  >  Class 8 Notes  >  Science Class 8  >  NCERT Summary: Combustion & Flame

Combustion & Flame Summary Class 8 NCERT Summary

Introduction

  • Fuels are used to get energy in the form of heat. Cow dung, wood, coal, charcoal, petrol, diesel, compressed natural gas (CNG), etc. are the examples of fuels.
  • Candle burns with a flame whereas coal does not.

Combustion

  • It is a chemical process in which a substance reacts with oxygen to give off heat and light.
  • Oxygen (in air) is essential for combustion.
  • Substances that burn in air are called combustible substances (also called fuels) and those that do not burn in air are non-combustible substances.

Ignition temperature

  • It is the lowest temperature at which a substance catches fire.

Inflammable substances

  • They have very low ignition temperature and can easily catch fire with flame.

Supporter of combustion

  • The gaseous environment that supports combustion of a combustible substance is called supporter of combustion.
  • Smaller the size of combustible particles, faster is the rate of combustion.
  • Nature of combustible substances: Inflammable substances burn faster as compared to substances such as wood.

Control of fire

  • Water is commonly used to extinguish fire. It is not suitable for fires involving oil, petrol, and electrical equipments.
  • For fires involving oil, petrol, and electrical equipments, carbon dioxide is the best extinguisher.

Types of combustion

(i) Rapid combustion

  • The combustion in which substances burn rapidly to produce heat and light. In rapid combustion, external heat must be supplied.

(ii) Spontaneous combustion

  • The combustion in which substances suddenly burst into flames, without the application of any apparent cause.

(iii) Explosion

  • The combustion in which sudden reactions take place on ignition of some substances to produce heat, light, and sound.

Zones of candle flame

  • Dark zone (middle zone), luminous zone (innermost zone), and non-luminous zone (outer zone).

Combustion & Flame Summary Class 8 NCERT Summary

  • A good fuel is one which is cheap is readily available burns easily in air at a moderate rate produces large amount of heat does not leave behind any undesirable substances.

Combustion & Flame Summary Class 8 NCERT Summary

Fuel efficiency

  • It is expressed in terms of calorific value. The unit is kilo joule per kg.

Calorific value

  • It is the amount of heat energy produced by complete combustion of 1 kg of a fuel.
  • It is expressed in Kilo joule per kg (kJ/kg).
The document Combustion & Flame Summary Class 8 NCERT Summary is a part of the Class 8 Course Science Class 8.
All you need of Class 8 at this link: Class 8
114 videos|389 docs|79 tests

FAQs on Combustion & Flame Summary Class 8 NCERT Summary

1. What is combustion?
Ans. Combustion is a chemical reaction that occurs between a fuel and an oxidizing agent, typically producing heat and light. It is a rapid oxidation process in which a substance combines with oxygen to release energy in the form of heat and light.
2. What are the products of combustion?
Ans. The products of combustion depend on the type of fuel being burned. Generally, the products include carbon dioxide (CO2), water vapor (H2O), and heat. However, incomplete combustion can also result in the production of carbon monoxide (CO) and soot.
3. How is a flame formed during combustion?
Ans. A flame is formed during combustion when the fuel vaporizes and mixes with oxygen in the air. The fuel molecules break down into smaller molecules, releasing energy in the form of heat and light. The heat causes the surrounding air to rise, creating convection currents that sustain the flame.
4. What factors affect the rate of combustion?
Ans. Several factors can affect the rate of combustion, including the availability of oxygen, the surface area of the fuel, the temperature, and the concentration of the fuel. The presence of a catalyst can also speed up the combustion process.
5. How does combustion contribute to air pollution?
Ans. Combustion of fossil fuels releases various pollutants into the atmosphere, including carbon dioxide, nitrogen oxides, sulfur dioxide, and particulate matter. These pollutants contribute to air pollution and can have harmful effects on human health and the environment. Additionally, the burning of biomass and waste materials can release pollutants such as carbon monoxide, volatile organic compounds, and hazardous air pollutants.
114 videos|389 docs|79 tests
Download as PDF
Explore Courses for Class 8 exam
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Download the FREE EduRev App
Track your progress, build streaks, highlight & save important lessons and more!
Related Searches

Free

,

pdf

,

mock tests for examination

,

practice quizzes

,

Exam

,

Extra Questions

,

Previous Year Questions with Solutions

,

video lectures

,

Sample Paper

,

Combustion & Flame Summary Class 8 NCERT Summary

,

MCQs

,

Viva Questions

,

Important questions

,

study material

,

Combustion & Flame Summary Class 8 NCERT Summary

,

ppt

,

Semester Notes

,

shortcuts and tricks

,

Objective type Questions

,

past year papers

,

Combustion & Flame Summary Class 8 NCERT Summary

,

Summary

;