9th Class (CBSE) Science: Natural Resources

Question: How are clouds formed?

Answer: The water evaporates due to heating up Of water bodies and other biological activities. The air also heats and rises. On rising, it expands and cools to form tiny droplets. These droplets grow bigger, expand and form clouds. The collection Of dust and other suspended particles facilitate the process.

Question: List any three human activities that you think would lead to air pollution.

Answer: Human activities that would lead to air pollution

1. Excessive use and burning of fossil fuels like coal and petroleum produces different oxides of nitrogen and sulphur. These are not only dangerous to our respiratory system but also leads to acid rain.
2. Incomplete combustion of various fuels forms unburnt carbon particles which lowers the visibility, especially in cold weather when water also condenses Out of air. This is known as smog and is a visible indication Of air pollution.
3. Large usage Of automobiles and improperly tuning of engines leads to the formation of carbon monoxide gas and Other oxides of nitrogen which causes lot of respiratory problems.
4. Forest fires, excessive mining and ore refining, excessive use of chlorofluorocarbons and excessive industrialization leads to air pollution.

Question: Why do organisms need water?

Answer: Organisms need water due to the following

1. All cellular processes take place in a water medium.
2. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.
3. Substances are also transported from one part of the body to the other in a dissolved form.
4. Water makes up about 70% of body weight Of all living organisms.
5. It helps in the digestion of food and absorption of nutrients in the blood. Hence, organisms need to maintain the level of water within their bodies in order to stay alive. It helps in maintaining body temperature.

Question: What is the major source of freshwater in the city / town / village where you live?

Answer: The major sources of freshwater in the city / town / village is the underground water which is mostly taken out with the help of hand pumps or tube wells. The rivers flowing in the nearby areas, lakes and ponds also serve as the source of freshwater.

Question: DO you know any activity which may be polluting these water sources?

Answer: There are many activities which cause pollution Of water sources such as:

1. Dumping of waste from factories, sewage from our towns and cities into rivers or lakes.
2. Discharging hot water from cooling towers into the water bodies affect the breeding capacity of aquatic organisms.

Question: How is soil formed?

Answer: The formation of soil takes place in this way:

Over long periods of time, thousands and millions Of years, the rocks at or near the surface of the are broken down by various physical, chemical and some biological processes. The end product of this breaking down is the fine particles of soil. There are many other factors which play a vital role in the formation of soil. These factors are :

1. The Sun: It causes heating of rocks which causes cracking and ultimately breaking up into smaller pieces.
2. Water: It breaks rocks both by freezing and fast flow.
3. Wind: It causes erosion of rocks similar to as done by fast flowing water. It also carries sand from one place to the other like water does.
4. Living organisms: Lichens and moss plants grow on the rock surface and cause rock surface to powder down and form a thin layer of soil. The roots of big trees sometimes go into cracks in the rocks and as the roots grow bigger, the crack is forced bigger.

Question: What is soil erosion?

Answer: The removal of topsoil which is rich in humus and nutrients by flowing water or wind is known as soil erosion. If this process continues further then all soil may get washed away and the rocks underneath may get exposed. It may lead to the loss of all valuable resources because nothing grows as such on the rocks.