NCERT Class VIII Science Solutions: Chapter 6-Combustion and Flame Part 4

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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.

Image of combustible substances

Examples of Combustible Substances

Image of 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)
Match the Column A and Column B.(Q)

Column A

Column 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)
Match the Column A and Column B.(A)

Column A

Column B

Oxides of sulphur and nitrogen

iv Acid rain

CNG

vi Fuel for automobiles.

Oxygen

v Necessary for combustion

Inflammable substance

iii Very low ignition temperature

Carbon dioxide

i Fire extinguisher

Carbon monoxide

ii Incomplete combustion of coal

Question 24:

Match the following for the flame of a candle.

Column a and Column B and Column C
Column A and Column B and Column C

Column A

Column 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 A and Column B and Column C

Column A

Column B

(zone)

Column C

(colour)

  1. Hottest part

iii Outer zone of complete combustion

a Blue

  1. Moderately hot

ii Middle zone of partial combustion

c Yellow

  1. Least hot

i Innermost zone of unburnt wax vapours

b Black

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