VI. Long Answer Questions
1. What do you mean by a fuel? What are the main characteristics of an ideal fuel?
2. With the help of a neat and labelled diagram, discuss the structure of a candle flame.
3. Discuss the harmful effects of burning fuel on our environment.
4. What is global warming? How does it affect our environment?
Answers
Answer:
Explanation:
1. The substances which act as energy sources are known as fuels.
The main characteristics of an ideal fuel are -
i) The fuel should have high calorific value.
ii) The fuel should have proper ignition temperature.
iii) The rate of combustion should be balanced and moderate.
iv) The content of non-volatile substances should be low as possible.
v) The fuel should be available at low cost.
3. The harmful effects of burning fuel on our environment are-
i) Carbon fuels such as wood, coal, petroleum release unburnt carbon particles in the environment. These particles are very dangerous pollutants and cause respiratory diseases for example asthma.
ii) The combustion of fossil fuels also releases a large amount of carbon dioxide in the atmosphere. carbon dioxide is a greenhouse gas which is responsible for global warming.
Global warming is a rise in the overall temperature of earth's surface. This leads to melting of polar caps and rise in the sea level and further results in flooding of coastal regions.
iii) when fuels are incompletely burnt, they release carbon monoxide gas into the atmosphere. This gas is very dangerous as it is poisonous in nature. If we burn coal in a closed room, then the person sleeping in that room will be killed by the action of carbon monoxide.
iv) Burning of coal and diesel releases sulphur dioxide gas. This gas is extremely corrosive and suffocating in nature. Petrol gives off oxides of nitrogen. The oxides of sulfur and nitrogen get dissolved in rainwater and form acids. This is known as acid rain. This water is very harmful to plants, animals, and various monuments.
4. The increase in the temperature of the earth's atmosphere, caused by the increase of certain gases is known as global warming.
The effect of global warming or climate damage include far-reaching and long-lasting changes to the natural environment, to ecosystems and human societies caused directly or indirectly by human emissions of greenhouse gases. It also includes the economic and social changes which stem from living in a warmer world.