Consider the following statements regarding the composition of smoke: 1. It contains a mixture of gases and fine dust particles. 2. It is composed entirely of water vapour. 3. It is produced by the burning of fuel. Which of the statements given above is/are correct?

The correct option is (c). Explanation Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis. It is technically classified as an aerosol, specifically a solid dispersed in a gas. - Statement 1 is Correct: Smoke contains a mixture of gases (such as carbon dioxide, carbon monoxide, and nitrogen oxides) and fine solid particles (particulate matter like soot, ash, and unburnt carbon). - Statement 2 is Incorrect: Smoke is not composed entirely of water vapour. While water vapour is often a byproduct of combustion, smoke is characterized by the presence of particulate matter and combustion gases. A visible mass composed entirely of condensed water vapour is referred to as steam, mist, or fog. - Statement 3 is Correct: Smoke is produced by the burning of fuels (such as wood, coal, petroleum, or biomass). The density and composition of the smoke depend on the nature of the fuel and the efficiency of combustion (complete vs. incomplete). Key Takeaway: Smoke is a complex mixture of gases and fine solid particles resulting from combustion, distinct from water vapour which forms steam or clouds.

NCERT Class 6 Environment & Ecology — Chapter 2: Air around us

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Consider the following statements regarding the composition of smoke:

It contains a mixture of gases and fine dust particles.
It is composed entirely of water vapour.
It is produced by the burning of fuel.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 and 2 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (c).

Explanation

Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis. It is technically classified as an aerosol, specifically a solid dispersed in a gas.

Statement 1 is Correct: Smoke contains a mixture of gases (such as carbon dioxide, carbon monoxide, and nitrogen oxides) and fine solid particles (particulate matter like soot, ash, and unburnt carbon).
Statement 2 is Incorrect: Smoke is not composed entirely of water vapour. While water vapour is often a byproduct of combustion, smoke is characterized by the presence of particulate matter and combustion gases. A visible mass composed entirely of condensed water vapour is referred to as steam, mist, or fog.
Statement 3 is Correct: Smoke is produced by the burning of fuels (such as wood, coal, petroleum, or biomass). The density and composition of the smoke depend on the nature of the fuel and the efficiency of combustion (complete vs. incomplete).

Key Takeaway: Smoke is a complex mixture of gases and fine solid particles resulting from combustion, distinct from water vapour which forms steam or clouds.

Your note

More from Chapter 2: Air around us

Consider the following statements regarding the atmosphere: 1. It is a thin layer of air that surrounds the earth. 2. It extends only up to 10 km above the surface of the earth. 3. The air becomes denser as we move higher in the atmosphere. Which of the statements given above is/are correct?

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With reference to the composition of air, consider the following statements: 1. Nitrogen and oxygen together make up approximately 99% of the air. 2. Carbon dioxide constitutes the majority of the remaining 1% of air. 3. The composition of air varies from place to place. Which of the statements given above is/are correct?

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Consider the following statements regarding water vapour in the air: 1. Air contains water vapour only during the rainy season. 2. When air comes in contact with a cool surface, water vapour condenses. 3. The presence of water vapour in air is essential for the water cycle in nature. Which of the statements given above is/are correct?

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With reference to the burning of fuel and its by-products, consider the following statements: 1. Burning can occur in the absence of oxygen if nitrogen is present. 2. Burning of fuel produces smoke which contains a few gases and fine dust particles. 3. Smoke produced by burning fuel is generally beneficial to respiratory health. Which of the statements given above is/are correct?

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Consider the following statements regarding the "dust particles" in the air: 1. Dust particles are always present in the air. 2. The presence of dust particles in air is constant irrespective of time and place. 3. Breathing through the mouth can allow harmful dust particles to enter the body. Which of the statements given above is/are correct?

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The correct option is (c).

Explanation

Statement 1 is Correct: Smoke contains a mixture of gases (such as carbon dioxide, carbon monoxide, and nitrogen oxides) and fine solid particles (particulate matter like soot, ash, and unburnt carbon).
Statement 2 is Incorrect: Smoke is not composed entirely of water vapour. While water vapour is often a byproduct of combustion, smoke is characterized by the presence of particulate matter and combustion gases. A visible mass composed entirely of condensed water vapour is referred to as steam, mist, or fog.
Statement 3 is Correct: Smoke is produced by the burning of fuels (such as wood, coal, petroleum, or biomass). The density and composition of the smoke depend on the nature of the fuel and the efficiency of combustion (complete vs. incomplete).

Key Takeaway: Smoke is a complex mixture of gases and fine solid particles resulting from combustion, distinct from water vapour which forms steam or clouds.