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

  3. Carbon dioxide is an excellent fire extinguisher. (True)

  4. 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

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)

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)

Hottest part

iii Outer zone of complete combustion

a Blue

Moderately hot

ii Middle zone of partial combustion

c Yellow

Least hot

i Innermost zone of unburnt wax vapours

b Black