The chapter Combustion and Flame deals with the science behind burning and the role of fuels in daily life. In this chapter students are going to learn about combustion, ignition temperature, and flame structure. The chapter also covers types of combustion and safety tips for handling fire.
This set of MCQs and match-the-following questions focuses on the key concepts of the chapter. It covers topics like calorific value, fire extinguishers, and the role of oxygen in combustion. The questions are simple, interactive, and will give an easy revision for students.
MCQ for Class 8 Science MCQ Questions and Answers.
Class 8 Science Chapter 4 MCQ Online Test Questions and Answers
Question 1. Combustion is a process in which a substance reacts with:
a) Hydrogen
b) Oxygen
c) Nitrogen
d) Carbon dioxide
Answer:
b) Oxygen – Combustion is a chemical reaction where a substance combines with oxygen to release heat and light.
Question 2. Substances that burn in air are called:
a) Non-combustible substances
b) Combustible substances
c) Metals
d) Alloys
Answer:
b) Combustible substances
Question 3. The lowest temperature at which a substance catches fire is known as:
a) Boiling point
b) Freezing point
c) Ignition temperature
d) Melting point
Answer:
c) Ignition temperature
Question 4. Which of the following is an example of an inflammable substance?
a) Water
b) Petrol
c) Sand
d) Glass
Answer:
b) Petrol
Question 5. Water cannot be used to extinguish fire caused by:
a) Wood
b) Paper
c) Petrol
d) Coal
Answer:
c) Petrol – Water is lighter than petrol, so petrol floats and keeps burning, spreading the fire further.
Question 6. Which gas is released during incomplete combustion?
a) Oxygen
b) Carbon dioxide
c) Carbon monoxide
d) Nitrogen
Answer:
c) Carbon monoxide
Question 7. The colour of the hottest part of a flame is:
a) Yellow
b) Blue
c) Red
d) Black
Answer:
b) Blue – The hottest part of a flame is blue due to complete combustion.
Question 8. The substance that does not form a flame when burned is:
a) Charcoal
b) Kerosene
c) Candle wax
d) Magnesium
Answer:
a) Charcoal
Question 9. The calorific value of LPG is approximately:
a) 17,000 kJ/kg
b) 33,000 kJ/kg
c) 55,000 kJ/kg
d) 60,000 kJ/kg
Answer:
c) 55,000 kJ/kg
Question 10. Which type of combustion occurs suddenly with heat, light, and sound?
a) Rapid combustion
b) Explosion
c) Spontaneous combustion
d) Slow combustion
Answer:
b) Explosion
Question 11. The main component of CNG is:
a) Propane
b) Methane
c) Ethane
d) Butane
Answer:
b) Methane
Question 12. Fire caused by electrical equipment is best extinguished using:
a) Water
b) Sand
c) Carbon dioxide
d) Petrol
Answer:
c) Carbon dioxide
Question 13. The chemical process involved in burning is:
a) Neutralisation
b) Oxidation
c) Reduction
d) Combustion
Answer:
d) Combustion
Question 14. Which zone of a candle flame has unburnt carbon particles?
a) Blue zone
b) Luminous zone
c) Dark zone
d) Outer zone
Answer:
b) Luminous zone
Question 15. Global warming is primarily caused by the increased concentration of:
a) Nitrogen
b) Oxygen
c) Carbon dioxide
d) Helium
Answer:
c) Carbon dioxide – Excess carbon dioxide traps heat in the atmosphere, leading to global warming.
Question 16. Which fuel has the highest calorific value?
a) Hydrogen
b) Petrol
c) LPG
d) Wood
Answer:
a) Hydrogen – Hydrogen has the highest calorific value, releasing maximum energy per unit mass.
Question 17. The combustion that occurs on its own without external heating is called:
a) Rapid combustion
b) Explosion
c) Spontaneous combustion
d) Slow combustion
Answer:
c) Spontaneous combustion
Question 18. In a fire extinguisher, carbon dioxide is stored as:
a) A gas
b) A liquid
c) Solid dry ice
d) Powder
Answer:
b) A liquid
Question 19. Which part of the flame is used by goldsmiths for melting gold and silver?
a) Luminous zone
b) Dark zone
c) Non-luminous zone
d) Inner zone
Answer:
c) Non-luminous zone – Goldsmiths use the non-luminous zone as it is the hottest and produces less soot.
Question 20. Acid rain is caused by the oxides of:
a) Sulphur and nitrogen
b) Carbon and nitrogen
c) Oxygen and hydrogen
d) Carbon and oxygen
Answer:
a) Sulphur and nitrogen – Acid rain forms when sulphur and nitrogen oxides mix with water to make acids.
Question 21. A good fuel produces:
a) Maximum smoke
b) High energy and minimal residue
c) No heat
d) Pollution
Answer:
b) High energy and minimal residue
Question 22. Which gas is used in fire extinguishers?
a) Nitrogen
b) Carbon dioxide
c) Oxygen
d) Methane
Answer:
b) Carbon dioxide
Question 23. The ignition temperature of a substance is:
a) Very high
b) Very low
c) Specific for each substance
d) Not required for combustion
Answer:
c) Specific for each substance
Question 24. The outermost zone of a flame is:
a) Hottest and blue
b) Coolest and yellow
c) Dark and hot
d) Black and cold
Answer:
a) Hottest and blue – The outer zone is blue and the hottest due to complete burning.
Question 25. The burning of coal releases:
a) Sulphur dioxide
b) Carbon monoxide
c) Carbon dioxide
d) All of the above
Answer:
d) All of the above – Coal can emit CO₂ (complete combustion), CO (incomplete), and SO₂ (due to sulfur in coal)
Question 26. Which material forms a flame when burned?
a) Charcoal
b) Magnesium
c) Kerosene oil
d) Both b and c
Answer:
d) Both b and c – Magnesium and kerosene vaporize while burning, so they produce a visible flame; charcoal only glows.
Question 27. Which is an example of rapid combustion?
a) Burning coal slowly
b) Lighting an LPG stove
c) Rusting of iron
d) Melting ice
Answer:
b) Lighting an LPG stove – Lighting an LPG stove is rapid combustion because it releases heat and light instantly.
Question 28. The dark zone of a flame contains:
a) Partially burnt fuel
b) Unburnt wax vapors
c) Fully burnt fuel
d) Oxygen
Answer:
b) Unburnt wax vapors – The dark zone has unburnt wax vapors that haven’t yet ignited.
Question 29. Fire extinguishers for electrical fires contain:
a) Water
b) Sand
c) Carbon dioxide
d) Petrol
Answer:
c) Carbon dioxide – CO₂ is used for electrical fires as it cuts off oxygen without conducting electricity.
Question 30. Which zone of a flame has maximum temperature?
a) Outer zone
b) Luminous zone
c) Dark zone
d) Inner zone
Answer:
a) Outer zone – The outer zone is the hottest as fuel burns completely with ample oxygen.
Question 31 – Match the Following
| Column A | Column B |
|---|---|
| 1. Ignition temperature | A. Produces carbon dioxide |
| 2. Rapid combustion | B. Very low ignition temperature |
| 3. Inflammable substances | C. Energy released during burning |
| 4. Calorific value | D. Lowest temperature for combustion |
| 5. Complete combustion | E. LPG burns instantly |
Answer:
| Column A | Correct Answer |
|---|---|
| 1. Ignition temperature | D. Lowest temperature for combustion |
| 2. Rapid combustion | E. LPG burns instantly |
| 3. Inflammable substances | B. Very low ignition temperature |
| 4. Calorific value | C. Energy released during burning |
| 5. Complete combustion | A. Produces carbon dioxide |
Other Chapter for MCQ questions for Class 8 Science
- Crop Production and Management Class 8 MCQ Questions
- Microorganisms: Friend and Foe Class 8 MCQ Questions
- Coal and Petroleum Class 8 MCQ Questions
- Conservation of Plants and Animals Class 8 MCQ Questions
- Reproduction in Animals Class 8 MCQ Questions
- Reaching the Age of Adolescence Class 8 MCQ Questions
- Force and Pressure Class 8 MCQ Questions
- Friction Class 8 MCQ Questions
- Sound Class 8 MCQ Questions
- Chemical Effects of Electric Current Class 8 MCQ Questions
- Some Natural Phenomena Class 8 MCQ Questions
- Light Class 8 MCQ Questions
