Combustion and Flame Class 8 MCQs Questions with Answers
I. Choose the correct option.
Question 1.
Which of the following fuels is used for running automobiles?
(a) CNG
(b) Petrol
(c) Both (a) and (b)
(d) Wood
Answer
Answer: (c) Both (a) and (b)
Question 2.
Magnesium burns to form
(a) calcium carbonate
(b) magnesium oxide
(c) calcium oxide
(d) magnesium sulphate
Answer
Answer: (b) magnesium oxide
Question 3.
Coal burns to produce
(a) calcium bicarbonate
(b) magnesium
(c) carbon dioxide
(d) oxygen
Answer
Answer: (c) carbon dioxide
Question 4.
Name the chemical process in which a substance reacts with oxygen to give out heat.
(a) Reaction
(b) Junction
(c) Combustion
(d) All of these
Answer
Answer: (c) Combustion
Question 5.
The substance that undergoes combustion is said to be
(a) burning
(b) flame
(c) charcoal
(d) combustible
Answer
Answer: (d) combustible
Question 6.
Combustible substances are also known as
(a) inflammable
(b) flaming
(c) illuminous
(d) non-flammable
Answer
Answer: (a) inflammable
Question 7.
Which of the following is a combustible?
(a) Stone piece
(b) Wood
(c) Glass
(d) None of these
Answer
Answer: (b) Wood
Question 8.
In the sun, light and heat are produced by
(a) chemical reactions
(b) nuclear reactions
(c) burning reactions
(d) bunsen burner
Answer
Answer: (b) nuclear reactions
Question 9.
Lowest temperature at which a substance catches fire is known as
(a) lowest temperature
(b) burning temperature
(c) ignition temperature
(d) flaming temperature
Answer
Answer: (c) ignition temperature
Question 10.
Long, long ago, which of the following trees was used to produce matchsticks?
(a) Mango
(b) Deodar
(c) Banyan
(d) Pine
Answer
Answer: (d) Pine
Question 11.
Which chemical is used in the rubbing surface provided for matchsticks?
(a) Sulphur
(b) Gold
(c) Red phosphorus
(d) White phosphorus
Answer
Answer: (c) Red phosphorus
Question 12.
Substances which have very low ignition temperature and can catch fire easily are called
(a) flammable substances
(b) inflammable substances
(c) combustible substances
(d) all of these
Answer
Answer: (d) all of these
Question 13.
Which of the following is an example of inflammable substance?
(a) Iron
(b) Glass
(c) LPG
(d) Stone
Answer
Answer: (c) LPG
Question 14.
Which of the following are required essentially for producing fire?
(a) Glass, coal, water
(b) Fuel, coal, straw
(c) Fire, wood, burner
(d) Fuel, air, heat
Answer
Answer: (d) Fuel, air, heat
Question 15.
The most common element used as fire extinguisher is
(a) CO2
(b) oxygen
(c) phosphorus
(d) NO2
Answer
Answer: (a) CO2
Question 16.
Baking soda constitutes
(a) hydrogen chloride
(b) sodium oxide
(c) sodium bicarbonate
(d) oxygen
Answer
Answer: (c) sodium bicarbonate
Question 17.
LPG means
(a) Liquefied Petroleum Gas
(b) Liquefied Petrol Gas
(c) Liquid Petrol Godown
(d) Liquid Petroleum Gas
Answer
Answer: (a) Liquefied Petroleum Gas
Question 18.
Phosphorus burns at
(a) room temperature
(b) 100°C
(c) cool temperature
(d) any temperature
Answer
Answer: (a) room temperature
Question 19.
‘Firework’ is an example of
(a) rapid combustion
(b) explosion
(c) spontaneous combustion
(d) slow combustion
Answer
Answer: (b) explosion
Question 20.
The calorific value of ‘hydrogen’ is
(a) 50,000 kJ/kg
(b) 55,000 kJ/kg
(c) 1,50,000 kJ/kg
(d) 6,000 kJ/kg
Answer
Answer: (c) 1,50,000 kJ/kg
II. Fill in the Blanks
Question 1.
The substance which vapourises during burning gives ………………..
Answer
Answer: flame
Question 2.
A good fuel should have ……………….. calorific value.
Answer
Answer: high
Question 3.
An example of slow combustion is ………………..
Answer
Answer: respiration
Question 4.
……………….. are substances that release energy on combustion.
Answer
Answer: Fuels
Question 5.
The most common supporter of combustion is ………………..
Answer
Answer: oxygen/air
Question 6.
Magnesium burns to change into ………………..
Answer
Answer: magnesium oxide
Question 7.
Wood is an example of ……………….. fuel.
Answer
Answer: solid
Question 8.
……………….. is an example of liquid fuel.
Answer
Answer: Kerosene
Question 9.
Carbon dioxide is ……………….. than oxygen.
Answer
Answer: heavier
Question 10.
Oxides of ……………….. and nitrogen causes acid rain.
Answer
Answer: sulphur
Question 11.
The increase in amount of ……………….. gas in atmosphere results in global warming.
Answer
Answer: carbon dioxide
Question 12.
Inflammable substances have very low ……………….. temperature.
Answer
Answer: ignition
Question 13.
The ……………….. zone of a flame is the hottest.
Answer
Answer: non-luminous
Question 14.
During combustion, generally, ……………….. and ……………….. energies are produced.
Answer
Answer: heat, light
Question 15.
LPG has a calorific value of ……………….. kJ/kg.
Answer
Answer: 55,000
III. True or False
Question 1.
Automobiles run only by using petrol.
Answer
Answer: False
Question 2.
CNG means ‘Connecting Neutral Gas’.
Answer
Answer: False
Question 3.
Coal burns with a flame.
Answer
Answer: False
Question 4.
Magnesium burns to produce magnesium oxide.
Answer
Answer: True
Question 5.
Combustion is a physical process.
Answer
Answer: False
Question 6.
The substance that undergoes combustion is said to be combustible.
Answer
Answer: True
Question 7.
Fuel may be solid, liquid or gas.
Answer
Answer: True
Question 8.
Wood is combustible.
Answer
Answer: True
Question 9.
A matchstick only contains white phosphorus.
Answer
Answer: False
Question 10.
Kerosene is an example of solid fuel.
Answer
Answer: False
Question 11.
For combustion, a substance must attain its ignition temperature.
Answer
Answer: True
Question 12.
The ignition temperature of phosphorus is 25°C.
Answer
Answer: True
Question 13.
LPG is an example of inflammable substances.
Answer
Answer: True
Question 14.
Water is a bad conductor of electricity.
Answer
Answer: False
Question 15.
Fuel, water and heat are three essential requirements for combustion.
Answer
Answer: False
Question 16.
The most common fire extinguisher is water.
Answer
Answer: True
Question 17.
Oxygen is heavier than CO2
Answer
Answer: False
Question 18.
The middle zone of a flame has yellow colour.
Answer
Answer: True
Question 19.
The calorific value of hydrogen is 1,50,000 kJ/kg.
Answer
Answer: True
Question 20.
Increase in nitrogen gas in atmosphere has led to ‘global warming’.
Answer
Answer: False
IV. Match the following
| Column I | Column II |
| 1. CNG | (a) Nuclear reactions |
| 2. Sun | (b) Compressed Natural Gas |
| 3. LPG | (c) Liquefied Petroleum Gas |
| 4. Fireworks | (d) Explosion |
| 5. Non-luminous zone | (e) Least hot |
| 6. Innermost zone | (f) Highest calorific value |
| 7. Combustion | (g) hottest |
| 8. Phosphorus | (h) combustible at 25°C |
| 9. Acid rain | (i) exothermic chemical reaction |
| 10. Hydrogen | (j) Oxides of nitrogen and sulphur |
Answer
Answer:
| Column I | Column II |
| 1. CNG | (b) Compressed Natural Gas |
| 2. Sun | (a) Nuclear reactions |
| 3. LPG | (c) Liquefied Petroleum Gas |
| 4. Fireworks | (d) Explosion |
| 5. Non-luminous zone | (g) hottest |
| 6. Innermost zone | (e) Least hot |
| 7. Combustion | (i) exothermic chemical reaction |
| 8. Phosphorus | (h) combustible at 25°C |
| 9. Acid rain | (j) Oxides of nitrogen and sulphur |
| 10. Hydrogen | (f) Highest calorific value |
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