Combustion and Flame Quiz - CBSE Class 8 Science

Free practice quiz: Combustion and Flame (CBSE Class 8 Science). 20 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This CBSE Class 8 Science practice quiz has 20 multiple-choice questions on Combustion and Flame, and 20 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. Which of the following is NOT required for combustion to occur?

   1. Fuel
   2. Oxygen
   3. Heat
   4. Water
   Show answer

   Answer: D. Water

   Combustion requires fuel, oxygen, and heat. Water is a product of combustion, not a requirement.

2. Why does a matchstick burn more rapidly when blown?

   1. Increased oxygen supply
   2. Increased heat
   3. Decreased oxygen supply
   4. Decreased heat
   Show answer

   Answer: A. Increased oxygen supply

   Blowing on a matchstick increases the supply of oxygen, which helps to accelerate the combustion process.

3. Describe the conditions necessary for spontaneous combustion.

   1. Low temperature and high oxygen
   2. High temperature and low oxygen
   3. High temperature and sufficient oxygen
   4. Low temperature and sufficient oxygen
   Show answer

   Answer: C. High temperature and sufficient oxygen

   Spontaneous combustion occurs when a substance ignites without any external ignition source due to slow oxidation which gradually generates heat. Sufficient oxygen is needed for this oxidation and a build-up of heat.

4. Analyze the effect of different factors (e.g., surface area, concentration of oxygen) on the rate of combustion.

   1. No impact on rate
   2. Factors have no predictable effect
   3. Increased surface area and oxygen concentration increase the rate
   4. Increased surface area decreases the rate, more oxygen increases the rate
   Show answer

   Answer: C. Increased surface area and oxygen concentration increase the rate

   Increased surface area provides more contact with oxygen, increasing the rate of combustion. Higher oxygen concentration provides more reactant, also increasing the combustion rate.

5. Explain the chemical reactions involved in the different zones of a candle flame.

   1. Only one reaction happens
   2. All zones have identical reactions
   3. Reactions differ due to varying oxygen availability and temperatures in different zones
   4. No chemical reactions occur
   Show answer

   Answer: C. Reactions differ due to varying oxygen availability and temperatures in different zones

   The innermost zone has incomplete combustion, the middle zone shows luminous flame due to incomplete combustion of wax vapors while the outermost zone has complete combustion.

More questions in this quiz

Answers and explanations are in the full quiz.

1. What is the luminous part of a candle flame?
2. What type of reaction is combustion?
3. Explain why a fire extinguisher uses carbon dioxide to put out a fire.
4. What is the difference between rapid combustion and explosion?
5. Explain the role of a wick in a candle.
6. How does the structure of a flame relate to the different zones of combustion?
7. Explain why some materials are more flammable than others.
8. Discuss the role of catalysts in combustion reactions.
9. Explain the concept of inflammable substances and give examples.
10. Compare and contrast complete and incomplete combustion. Give examples of each.
11. Explain the concept of fire triangle and its importance in fire prevention.
12. Discuss the various types of fire extinguishers and their suitability for different types of fires.
13. Describe the role of combustion in various industrial processes and its environmental impact.
14. Critically evaluate different methods for preventing and controlling fires, considering their effectiveness and limitations.
15. Analyze the contribution of combustion to global warming and suggest strategies for mitigation.

Browse all Combustion and Flame quizzes

More to play