Class 9 Science

Natural Resources

In Text Question Answer

Question 1. How is our atmosphere different from the atmospheres on Venus and Mars?

Answer: Atmospheres of Venus and Mars do not prevent the surface of these planets from being too hot during day and too cold during night. Earth’s atmosphere prevents the earth from becoming too hot or too cold. Thus, our atmosphere makes the earth a conducive place for life.

Question 2. How does the atmosphere act as a blanket?

Answer: Atmosphere is a bad conductor of temperature. Thus, it prevents the earth from becoming too hot during the day. Atmosphere also prevents solar radiation from escaping the earth’s surface. Thus, it prevents the earth from becoming too cold during the night. Thus, atmosphere acts like a blanket.

Question 3. What causes winds?

Answer: Uneven heating of the earth’s surface causes convection currents in the air. This causes movement of air, i.e. winds.

Question 4. How are clouds formed?

Answer: Evaporation of water from oceans and other water bodies causes water vapours to rise in air. Water vapour condenses to become clouds.

Question 5. List any three human activities that you think would lead to air pollution.

Answer: Following human activities would lead to air pollution:

  • Burning of fuels in automobiles.
  • Burning of fuels in factories.
  • Dust from mining activities.

Question 6. Why do organisms need water?

Answer: All metabolic functions take place in presence of water. Hence, organisms need water.

Question 7. What is the major source of fresh water in the city/town/village where you live?

Answer: Groundwater

Question 8. Do you know of any activity which may be polluting this water source?

Answer: Sewage water is discharged in nearby fields. The contaminated water seeps down the ground to pollute groundwater.

Question 9. How is soil formed?

Answer: Soil if formed by weathering of rocks by various agents of weathering. The process takes place over thousands of years.

Question 10. What is soil erosion?

Answer: Removal of topsoil by agents of weathering is called soil erosion.

Question 11. What are the methods of preventing or reducing soil erosion?

Answer: Following methods help in preventing soil erosion:

  • Afforestation
  • Shelter belt planting
  • Terrace farming in hilly areas

Question 12. What are the different states in which water is found during the water cycle?

Answer: Solid, Liquid and Gas

Question 13. Name two biologically important compounds that contain both oxygen and nitrogen.

Answer: Protein and Amino acids

Question 14. List any three human activities which would lead to an increase in the carbon dioxide content of air.

Answer: Following human activities would lead to an increase in the carbon dioxide in air:

  • Burning of fossil fuels in automobiles.
  • Burning of fossil fuels in thermal power plants.
  • Burning of firewood in kitchens.

Question 15. What is the greenhouse effect?

Answer: Some gases trap solar radiation in atmosphere. This is called greenhouse effect.

Question 16. What are the two forms of oxygen found in the atmosphere?

Answer: Oxygen and Ozone

Exercise Question Answer

Question 1. Why is the atmosphere essential for life?

Answer: Atmosphere helps in maintaining ambient temperature on earth. It is a source of important raw materials for living beings, e.g. oxygen, carbon dioxide, nitrogen, etc. Atmosphere is an important conduit in the water cycle. Thus, atmosphere is essential for life.

Question 2. Why is water essential for life?

Answer: Living beings need water to carry out various metabolic activities. Hence, water is essential for life.

Question 3. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?

Answer: Soil provides the base on which plants can grow. Soil is the source of water and minerals for plants. We know that all other living beings depend on plants for food. Even aquatic animals take food from plants. Thus, aquatic animals are not independent of soil as a resource.

Question 4. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?

Answer: Data on various parameters are collected by satellites. The data is then analysed by computer to predict the weather.

Question 5. We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?

Answer: Air keeps on moving from one place to another. Similarly, water is also in constant motion through water cycle. So, pollution can easily travel through movement of air and water; anywhere in the world. This means that isolating human activities to a limited area is not going to help in reducing pollution.

Question 6. Write a note on how forests influence the quality of our air, soil and water resources.

Answer: Forests influence the quality of air, soil and water resources in many ways. Trees take carbon dioxide and give oxygen during photosynthesis. Thus, trees help in maintaining the balance of carbon dioxide and oxygen in air. Roots of trees make the soil porous and thus help in recharge of groundwater. Trees also help in precipitation by adding water vapour by means of transpiration. Trees hold the topsoil in place with their roots. Discarded parts of a tree get decomposed and contribute to humus in soil.


Matter in Our Surroundings

Anything that has both mass and volume is called matter. You can also say that anything which has mass and which occupies space is called matter.

Is Matter Around Us Pure?

Elements and compounds are pure substances. All other substances are mixtures which means they are not pure substances.

Atoms and Molecules

Read about law of conservation of mass, law of constant proportions and Dalton's atomic theory.

Structure of Atoms

Atom is made of three particles; electron, proton and neutron. These particles are called fundamental particles of an atom or sub atomic particles.

Cell: The Fundamental Unit of Life

A cell is capable of independent existence and can carry out all the functions which are necessary for a living being.

Tissue

A groups of cells which is meant for a specific task is called tissue. Tissues are the first step towards division of labour in complex organisms.

Diversity in Living Organisms

Without proper classification, it would be impossible to study millions of organisms which exist on this earth.

Motion

If an object changes its position with respect to a reference point with elapse of time, the object is said to be in motion.

Force & Laws of Motion

Force has numerous effects. Force can set a stationary body in motion. Force can stop a moving body.

Gravitation

Earth attracts everything towards it by an unseen force of attraction. This force of attraction is known as gravitation or gravitation pull.

Work & Energy

When force is exerted on an object and object is displaced, work is said to be done. It means work is the product of force and displacement.

Sound

Sound is a type of energy. Sound travels in the form of wave from one place to another.

Why Do We Fall Ill

Health is a state of physical, mental and social well being. A condition in which the affected person is unable to carry out normal activities is termed as disease.

Natural Resources

Resources which are obtained from nature are called natural resources. Examples: Air, water, soil, wood, etc.

Improvement in Food Production

Food security is said to exist when all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life.