Class 8 Combustion And Flame CBSE Questions & Answers

Class 8 · Combustion And Flame

This is Science Class 8 Combustion and Flame CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
Read the following statements :i) The ignition temperature for dry paper is low as compared to wet paper.ii) The ignition temperature for wet paper is low as compared to dry paper.
  • A
    both are correct
  • B
    statement i) is correct but ii) is wrong
    Correct
  • C
    statement ii) is correct but i) is wrong
  • D
    both are wrong
2
Combustion of fuels is done to obtain :
  • A
    Residues
  • B
    Energy
    Correct
  • C
    Water
  • D
    Gases
3
Read the following statements :i) Substance doesn
  • A
    statement i) is correct but ii) is wrong
    Correct
  • B
    both are wrong
  • C
    statement ii) is correct but i) is wrong
  • D
    both are correct
4
Temperature of water inside paper cup held above candle flame :
  • A
    rise due to heat transferred
    Correct
  • B
    increases as flame extinguishes
  • C
    remains the same as earlier
  • D
    falls due to heat transferred
5
Carbon dioxide released from extinguisher :i) is denser than airii) is lighter than airiii) concentrates oxygen in vicinityiv) dilutes oxygen in vicinity
  • A
    only ii & iii are correct
  • B
    only i & iv are correct
    Correct
  • C
    only ii & iv are correct
  • D
    only i & iii are correct
6
Some combustion reactions occur suddenly with evolution of large amount of gas. Such a combustion is:
  • A
    extension
  • B
    inflammation
  • C
    explosion
    Correct
  • D
    expulsion
7
Read the following statements :i) Substances that burn with flame are first converted into vapour.ii) Wax first melts and changes into vapour.
  • A
    both are correct
    Correct
  • B
    statement i) is correct but ii) is wrong
  • C
    statement ii) is correct but i) is wrong
  • D
    both are wrong
8
In the following cases fire can be extinguished by removing combustible substance except :
  • A
    a building on fire
    Correct
  • B
    a paper on fire
  • C
    a firecracker
  • D
    a wood log on fire
9
Read the following statements :i) Ignition temperature of kerosene is lower than that of petrol.ii) Ignition temperature is also known as critical temperature.
  • A
    both are wrong
    Correct
  • B
    statement i) is correct but ii) is wrong
  • C
    statement ii) is correct but i) is wrong
  • D
    both are correct
10
Some substances do not burn with a flame such as :
  • A
    Kerosene
  • B
    Charcoal
    Correct
  • C
    LPG
  • D
    Wax
11
If Bunsen burner
  • A
    blue
  • B
    green
  • C
    yellow
    Correct
  • D
    black
12
In a candle the part which serves as a fuel is :
  • A
    the matchstick
  • B
    the wick
  • C
    surrounding air
  • D
    the paraffin wax
    Correct
13
A flickering flame produces smoke due to :
  • A
    presence of ideal fuel
  • B
    absolute combustion
  • C
    partial combustion
    Correct
  • D
    high ignition temperature
14
When a fuel undergoes complete combustion it produces :
  • A
    smoky flame
  • B
    luminous flame
  • C
    non luminous flame
    Correct
  • D
    no any flame
15
At the base of flame, blue zone occurs due to :
  • A
    complete combustion of wax vapours
  • B
    burning of carbon monoxide
    Correct
  • C
    glowing of unburnt carbon particles
  • D
    presence of unburnt carbon particles