Science MCQ

Burning of fuels releases carbon dioxide in air in the environment. Increased percentage of carbon dioxide in air is causing global warming. Carbon dioxide gas in the air trap sun’s heat rays by producing greenhouse effect.

White phosphorus undergoes spontaneous combustion.
Hence it is not used in making matchsticks now days.

Biogas

Hydrogen gas has the highest calorific value.

The green leaves contain a lot of water. This water does not allow the green leaves to get heated to their ignition temperature and makes burning of green leaves difficult.

Carbon dioxide is lighter than air and forms a layer around the burning substance. It covers the fire like a blanket due to which fresh air cannot reach the burning substance.

Production of heat and light from hydrogen in the sun is a nuclear reaction.

If the clothes of a person working in the kitchen catch fire, the person is immediately covered with a blanket. When the burning clothes of a person are covered with a blanket, the supply of air to the burning clothes is cut off and hence the burning stops.

Asbestos is a non combustible substance and cannot catch fire on its own.

In the outer zone complete combustion of the fuel takes place and the colour of the flame is blue and is the hottest part of the flame.

White phosphorus undergoes spontaneous combustion. It catches fire on its own at room temperature.

Coke does not vapourise during burning and hence do not produce flame.

Due to the burning of coal, the available oxygen gets depleted and it leads to incomplete burning of coal. Incomplete combustion of coal gives carbon monoxide gas. It is a very poisonous gas. It is dangerous to burn coal in a closed room. The carbon monoxide gas produced can kill persons sleeping in that closed room.

Fires in underground coalmines occur due to spontaneous combustion of coal dust.

Carbon monoxide does not contribute to the formation of an acid rain.

Three zones