Science Question Answer (5 Marks)

1. Burning of white phosphorus in air at room temperature is a spontaneous combustion. The type of combustion in which a material suddenly bursts into flames, without the application of any apparent cause is called spontaneous combustion.
2. Burning of LPG is combustion in which a substance burns rapidly and produces heat and light with the help of external heat.
3. Ignition of a cracker is a combustion in which a substance burns suddenly and produces heat, light and sound with the help of heat or pressure.
4. Burning of coal dust in a coalmine is a spontaneous combustion. The type of combustion in which a material suddenly bursts into flames, without the application of any apparent cause is called spontaneous combustion.

In the middle zone, partial combustion of the fuel takes place, so the colour of the flame is yellow and it is moderately hot part of the flame. It is the luminous part of the flame. It is given in the following picture:

Global warming is the rise in temperature of earth atmosphere caused by the excessive amount of carbon dioxide in the air. Due to rise in the temperature of atmosphere, the ice in polar regions will melt very fast, producing a lot of water. 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. Rise in water may cause a rise in the sea level leading to floods in coastal areas. The low-lying areas may be completely submerged under water leading to loss of life and property.