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Class 8 Science MCQ Questions of Combustion and Flame with Answers?

Answer 1

Class 8 Science MCQ Questions of Combustion and Flame with Answers for significant part of exams for Class 8 Science and if practiced properly can help you to get higher marks. Refer to more Chapter-wise MCQ Questions for NCERT Class 8 Science and also download more latest study material for all subjects.

Practicing these MCQ Questions for class 8 science will help you to answer every question that is being asked in the exams. Students can solve these MCQ Questions to know their preparation level. Combustion and Flame Objective type Questions help the students to understand the concepts thoroughly and to score good marks.

 The MCQ Questions for Class 8 Science with answers have been prepared as per the latest syllabus, NCERT books and examination pattern suggested by CBSE. Practice it now and score high in exams Class 8 Science MCQ Questions of combustion and Flame with answers are given here.

Practice Class 8 Science MCQ Questions chapter-wise

1. The burning of LPG is an example of

(a) rapid combustion
(b) spontaneous combustion
(c) slow combustion
(d) explosion

2. A temperature at which the substance burns in absence of a spark or flame is called

(a) melting
(b) boiling temperature
(c) kindling temperature
(d) evaporation

3. Which of the following is a non-renewable energy source?

(a) Hydropower
(b) Tidal power
(c) Geothermal energy
(d) Nuclear energy

4. Which of the following is not a fossil fuel?

(a) Coal
(b) Alcohol
(c) Natural gas
(d) Petroleum gas

5. Which gas helps in the process of combustion?

(a) Cooking gas
(b) Nitrogen gas
(c) Oxygen gas
(d) Producer gas

6. The amount of heat energy produced on complete combustion of 1 kg of a fuel is called

(a) calorific value
(b) significant value
(c) heat value
(d) internal energy

7. Which zone represents the partial combustion in candle flame?

(a) Outer zone
(b) Middle zone
(c) Inner zone
(d) Lower zone

8. Burning coal in a closed room will produce

(a) nitrogen oxides
(b) carbon dioxide
(c) carbon monoxide
(d) oxygen

9. Substances that catch fire are called

(a) acids
(b) bases
(c) combustible
(d) burners

10. Out of these, which is able to control fires?

(a) NH₃
(b) H₂
(c) CO₂
(d) F₂

11. Which zone of a flame does a goldsmith use for melting gold and silver?

(a) Outer zone
(b) Middle zone
(c) Inner zone
(d) Lower zone

12. Which is a non-combustible substance?

(a) Wood
(b) Paper
(c) Iron nails
(d) Straw

13. Acid rain contains mainly

(a) oxygen and nitrogen gas
(b) fluorine and chlorine gas
(c) magnesium oxide
(d) nitrogen oxide and sulphur dioxide

14. Magnesium burns to form

(a) calcium carbonate
(b) magnesium oxide
(c) calcium oxide
(d) magnesium sulphate

15. In the sun, light and heat are produced by

(a) chemical reactions
(b) nuclear reactions
(c) burning reactions
(d) bunsen burner

16. Long, long ago, which of the following trees was used to produce matchsticks?

(a) Mango
(b) Deodar
(c) Banyan
(d) Pine

17. Which chemical is used in the rubbing surface provided for matchsticks?

(a) Sulphur
(b) Gold
(c) Red phosphorus
(d) White phosphorus

18. Which of the following examples represents explosion?

(a) Burning of matchstick
(b) Burning of cooking gas
(c) Ignition of a cracker
(d) Burning of phosphorus in air at room temperature

19. A flame has

(a) one zone
(b) two zones
(c) three zones
(d) four zones

20. Unburnt carbon particles cause

(a) stomach infections
(b) respiratory problems
(c) brain infections
(d) throat problems

21. The suspended particles released by the combustion of coal in the air may lead to a health disease. Select the correct option.

(a) Goitre
(b) Arthritis
(c) Asthma
(d) Bone cancer

22. The colour of outer zone of candle flame is

(a) orange
(b) blue
(c) red
(d) yellow

23. Arrange the different regions of a flame in increasing order of temperature.

(a) Middle region < inner region < outermost region
(b) Outermost region < inner region < middle region​
(c) Inner region < outermost region < middle region
(d) Inner region < middle region < outermost region

24. Combustion is a _____ chemical reaction:

(a) volatile
(b) exothermic
(c) endothermic
(d) none of the above

25. No external heat is required to start :

(a) simultaneous combustion
(b) spontaneous combustion
(c) splendid combustion
(d) spreading fire combustion

Answer 2

1. Answer: (a) rapid combustion

Explanation: LPG burns rapidly and produces heat and light. When the gas burns in air it is a chemical change. Combustion of LPG is a chemical change because, after its combustion, the new substance formed changes chemically and cannot be turned back into LPG. Therefore, Burning of LPG is an example of rapid combustion.

2. Answer:  (c) kindling temperature

Explanation:The minimum temperature needed for self-sustained combustion in absence of a spark or flame, at which the vapours from a volatile liquid will ignite spontaneously.

3. Answer: (d) Nuclear energy

Explanation: Energy sources are of two categories, renewable and non renewable. 
Non renewable resources include fossil fuels (petroleum, natural gas, coal) and nuclear fuel (mostly uranium, which is in limited supply). Use of both of them causes pollution. Fossil fuel cause oil spills, acid rain, air pollution, water pollution etc. Nuclear energy may give rise to radiation pollution. Renewable resources of energy include biomass energy and some forms of inexhaustible energy like solar energy, hydro power, wind power etc. They are less polluting but far more expensive due to technological incipiency.

4. Answer: (b) Alcohol

Explanation: Coal, natural gas and petroleum gas are fossil fuels, all were formed due to decomposition of dead animals and plants million of years ago.

5. Answer: (c) Oxygen gas

Explanation: Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat. The original substance is called the fuel, and the source of oxygen is called the oxidizer.

6. Answer: (a) calorific value

Explanation:The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its Calorific value.

7. Answer: (b) Middle zone

Explanation:In a candle flame, the partial combustion portion is in the middle zone of the flame. The yellow color in the middle portion of the candle depicts partial combustion. This region is partially hot. Hence, the middle zone represents the partial combustion in a candle flame.

8. Answer: (b) carbon dioxide

Explanation: Incomplete combustion of fuels produces carbon monoxide gas. It is dangerous to burn coal in a closed room because it produces carbon monoxide gas, which can kill persons sleeping in that room.

9. Answer: (c) combustible

Explanation: Burners on ignition provide energy in the form of heat and light. Example of burner is Bunsen burner. Combustible substances hold ability to catch fire. Example of combustible substances are cloth, kerosene oil etc.

10. Answer: (c) CO₂

Explanation: CO₂ is a non-combustible gas and it is also non-supporter of combustion. It extinguishes fire in two ways: 

(i) Since it is heavier than oxygen, it covers the fire like a blanket and cuts off the contact between oxygen and fuel. 

(ii) In cylinders,CO2 is kept in the liquid form. When released, it expands enormously and cools down. This brings down the temperature of the fuel, which helps in controlling the fire. 

11. Answer: (a) Outer zone

Explanation: A goldsmith uses the outermost zone of a flame, which is non-luminous, to melt gold and silver as it is the hottest zone of the flame, having more temperature.

12. Answer: (c) Iron nails

Explanation: Glass, iron nail and stone piece will not burn like wood hence they are not combustible. Wood burns in air and it is called the combustible substance.

13. Answer: (d) nitrogen oxide and sulphur dioxide

Explanation: Air pollution from burning of fossil fuels is the major cause of acid rain. The main chemicals in air pollution that create acid rain are sulfur dioxide (SO2) and nitrogen oxides. Acid rain usually forms high in the clouds where sulfur dioxide and nitrogen oxides react with water, oxygen, and oxidants. this mixture forms a mild solution of sulfuric acid and nitric acid. Sunlight increases the rate of most of these reactions. Rainwater, snow, fog, and other forms of precipitation containing those mild solutions of sulfuric and nitric acids fall to earth as acid rain.

14. Answer: (b) magnesium oxide

Explanation: When the magnesium metal burns it reacts with oxygen found in the air to form Magnesium Oxide. After it burns, it forms a white powder of the magnesium oxide. Magnesium gives up two electrons to oxygen atoms to form this powdery product.

15. Answer: (b) nuclear reaction

Explanation: Sun produces heat and light by nucleur reactions i.e. nuclear fusion of hydrogen into helium in its core.

Answer 3

16. Answer: (d) Pine

Explanation:  White pine and aspen are two common woods used making matchsticks.

17. Answer: (c) Red phosphorus

Explanation:The striking surface of the matchbox contains red phosphorus and the head of the matchstick contains potassium chlorate. So when the matchstick is rubbed on the matchbox, some of the red phosphorus is converted to white phosphorus, a chemical i.e. so volatile that it ignites in air.

18. Answer: (c) Ignition of a cracker

Explanation: Ignition of a cracker is an example of explosion. When a cracker is ignited, large amount of heat, light, gas and sound are released due to a sudden reaction. The burning of phosphorus in air at room temperature is an example of spontaneous combustion. Burning of matchstick and burning of cooking gas are examples of rapid combustion.

19. Answer: (c) three zones

Explanation: Candles produce light by releasing heat. A candle flame consists of three zones. Each zone has different temperatures and colors.

(i) The first zone is called the outer zone.

(ii) The second zone is called the middle zone. 

(iii) The third zone is called the Inner zone

20. Answer: (b) respiratory problems

Explanation:  Unburnt carbon particles causes respiratory problems. They cause respiratory diseases, such as asthma. Unburnt carbon particles in air are dangerous pollutants. They are obtained during incomplete combustion of fuel.

21. Answer: (c) Asthma

Explanation: Suspended particulate matter (SPM) refers to microscopic solid or liquid matter suspended in the Earth’s atmosphere. Air pollutants consist of gaseous pollutants, odours, and SPM, (suspended particulate matter) such as dust, fumes, mist, and smoke. The high concentration of these in and near urban areas causes severe pollution to the surroundings. A high amount of SPM in air leads to respiratory problems and lung-related diseases like asthma.

22. Answer: (b) blue

Explanation:The outer zone of a candle flame is blue in colour. It is where complete combustion takes place.

23. Answer: (d) Inner region < middle region < outermost region

Explanation:The inner region of a flame mostly has vapourised wax and very little burning takes place there, so its temperature is lowest. The middle region undergoes partial burning and therefore has an intermediate temperature. The outermost region gets maximum oxygen supply and complete combustion takes place. So, the temperature is maximum in the outermost region.

24. Answer: (b) exothermic

Explanation: A combustion reaction is when all substances in a compound are combined with oxygen, which then produces carbon dioxide and water. Combustion is commonly called burning. It is an exothermic reaction, which means heat is produced and is easily distinguished. Combustion occurs predominantly in auto-mobiles, homes, and in factories.Hence it is an exothermic reaction.

25. Answer: (b) spontaneous combustion

Explanation:Spontaneous combustion is a combustion in which no external heat is given is known as spontaneous combustion. For example: Burning of white phosphorus in air.

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