NCERT Class VIII Science Solutions: Chapter 6-Combustion and Flame Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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SHORT ANSWER QUESTIONS

Question 21:

Boojho wants to separate the following materials as combustible and non-combustible. Can you help him?

Charcoal, chalk, stone, iron rod, copper coin, straw, cardboard, glass, paper, candle, wood.

Answer:

  1. Combustible - charcoal, straw, card board, paper, candle wood,
  2. Non-combustible - chalk, stone, iron rod, copper coin, glass.
Combustible Substances

Question 22:

Indicate whether the following statements are true or false. Also write the false statements in their correct form.

  1. Air is necessary for combustion.
  2. Magnesium is a non-combustible metal.
  3. Carbon dioxide is an excellent fire extinguisher.
  4. Calorific value of wood is higher than that of coal.

Answer:

  1. Air is necessary for combustion. (True)
  2. Magnesium is a non-combustible metal. (False)

Hint: Magnesium is a combustible metal

  1. Carbon dioxide is an excellent fire extinguisher. (True)
  2. Calorific value of wood is higher than that of coal. (False)

Hint: Calorific value of coal is higher than that of wood.

Question 23:

Match the items of Column A with the items of Column B.

Match the Column a and Column B. (Q)
Column AColumn B
  1. Oxides of sulphur and nitrogen
  • Fire extinguisher
  • CNG
  • Incomplete combustion of coal
  • Oxygen
  • Very low ignition temperature
  • Inflammable substance
  • Acid rain
  • Carbon dioxide
  • Necessary for combustion
  • Carbon monoxide
  • Fuel for automobiles.

Answer:

Match the Column a and Column B. (A)
Column AColumn B
Oxides of sulphur and nitrogeniv Acid rain
CNGvi Fuel for automobiles.
Oxygenv Necessary for combustion
Inflammable substanceiii Very low ignition temperature
Carbon dioxidei Fire extinguisher
Carbon monoxideii Incomplete combustion of coal

Question 24:

Match the following for the flame of a candle.

Column a and Column B and Column C
Column AColumn B

(zone)

Column C

(colour)

  1. Hottest part
  • Innermost zone of unburnt wax vapours
  • Blue
  • Moderately hot
  • Middle zone of partial combustion
  • Black
  • Least hot
  • Outer zone of complete combustion
  • Yellow

Answer:

Column a and Column B and Column C
Column AColumn B

(zone)

Column C

(colour)

  1. Hottest part
iii Outer zone of complete combustiona Blue
  1. Moderately hot
ii Middle zone of partial combustionc Yellow
  1. Least hot
i Innermost zone of unburnt wax vapoursb Black