Alert: You are not allowed to copy content or view source
Check Exam Dates here | See Marking Scheme here | Frequently Asked Questions (FAQs) | Buy Practice Papers for CREST Olympiads here | Last Date for CREST Reasoning Olympiads (CRO) Registration is 20th June 2019 | CREST Reasoning Olympiads (CRO) is scheduled for June/July. Apply now

Was this article Helpful?

Combustion and Flame

Combustion and Flame
science Square
Science Square

Combustion

  • Combustion is a chemical reaction where heat gets released through a material when it gets reacted with oxygen.
  • A combustible substance is one which undergoes combustion.
  • Combustible substance is also known as fuel
  • It may be in the form of solid, liquid, or gas.

Science Class 8 Combustion and Flame

Ignition temperature

  • It is the minimum temperature at which the clothes of any material catch fire.
  • The ignition temperature has to be higher than the temperature of the combustible substance for the substance to get burn.

Science Class 8 Combustion and Flame

Inflammable substances

  • Inflammable substance easily catches fire as they have low ignition temperature.
  • For example – LPG, petrol, etc.

Science Class 8 Combustion and Flame

Things necessary for combustion to take place

  • Fuel
  • Temperature
  • Air

Measures to control fire

  1. Fire brigade stations
  • These stations cool down the fire by sprinkling water on the areas affected.
  • The water sprinkled brings down the temperature below the ignition.

Science Class 8 Combustion and Flame

  1. Fire extinguisher
  • The most common fire extinguisher is water which works on paper, wood, etc.
  • In cases of fire due to oil, petrol, water is not good; in this case Carbon dioxide is used as an extinguisher.

Science Class 8 Combustion and Flame

  1. Use of blankets
  • Blankets can also be used as a fire extinguisher.

Science Class 8 Combustion and Flame

Different types of combustion

  1. Rapid combustion
  • The substances catch fire easily and burn very fast. They also yield heat and light.
  1. Spontaneous combustion
  • Suddenly the substances get into the flames without any specific reason in a spontaneous combustion.
  1. Explosion
  • Reaction in this type of combustion suddenly results into light, heat, and sound.
  1. Flame
  • When substances vaporize on heating, flames get generated.

Fuel

  • Fuel is a substance that undergoes the process of combustion.
  • Examples are charcoal, petrol, wood, kerosene, etc.

Science Class 8 Combustion and Flame

Characteristics of a good fuel

  • It has to be cheap
  • It should be quite simply available.
  • Large amount of heat should get generated.
  • After combustion, any unwanted matter should not be left behind.

Fuel efficiency

  • Calorific value is the amount of heat generated on combustion of around 1 kg of a fuel.
  • The unit is kilojoule per kg (kj / kg)

Harmful effects of burning fuel

  • Various carbon particles get released in the air causing respiratory diseases.
  • Global warming
  • Acid rain

Science Class 8 Combustion and Flame

Recap

  • Combustion is a chemical reaction where heat gets released through a material when it gets reacted with oxygen.
  • A combustible substance is one which undergoes combustion.
  • It is the minimum temperature at which the clothes of any material catch fire.
  • Fuel is a substance that undergoes the process of combustion.
  • Examples are charcoal, petrol, wood, kerosene, etc.
  • Calorific value is the amount of heat generated on combustion of around 1 kg of a fuel.
  • The unit is kilojoule per kg (kj / kg).

 

Comments

Please to write a comment.

Quiz for Combustion and Flame

Q.1

Name the compound present in the head of the match stick.

a) Potassium chlorate and Antimony trisulphide
b) Antimony sulphide
c) White phosphorous and potassium chlorate
d) Red phosphorous and potassium chlorate

Q.2

Which one doesn't burn with a flame?

a) Kerosene
b) Coal
c) Candle
d) Molten wax

Q.3

A chemical process in which a substance reacts with oxygen to give off heat is _______.

a) Respiration
b) Transpiration
c) Combustion
d) Inhalation

Q.4

In the Sun, heat and light are produced by ____________.

a) Combustion
b) Explosion
c) Conduction
d) Nuclear reaction

Q.5

Which one is a cleaner fuel in automobiles?

a) CNG
b) Petrol
c) LPG
d) Diesel

Q.6

Which one is a very poisonous gas?

a) Carbon dioxide
b) Carbon monoxide
c) Oxygen
d) Hydrogen

Q.7

Global warming is the result of _______.

a)

Increased petrol

b)

Increased oxygen

c)

Increased Carbon monoxide

d)

Increased Carbon dioxide

Q.8

The unit of calorific value:

a) KG/g
b) Kg/KJ
c) KJ/Kg
d) g/KJ

Q.9

The calorific value of CNG when compared to LPG is:

a) Less
b) More
c) Same
d) No calorific value

Q.10

The color of outer zone of the candle flame is:

a) Orange
b) Yellow
c) Blue
d) Black

Your Score: 0/10

Other Chapters of Class 8

  EXPLORE  

70%