Class 9 Science - Chapter Natural Resources NCERT Solutions | What are the two forms of oxygen found i

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

What causes winds?

Why is the atmosphere essential for life?

Why do organisms need water?

Why is water essential for life?

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?

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

How does the atmosphere act as a blanket?

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

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

Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupees coin and a one-rupee coin?

State the universal law of gravitation.

Which of the following are matter?

Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.

A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force (Fig. 11.3). Let us take it that the force acts on the object through the displacement. What is the work done in this case?

What is meant by a pure substance?

How does the sound produced by a vibrating object in a medium reach your ear?

In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium observations are in agreement with the law of conservation of mass.

sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water

What are canal rays?

State any two conditions essential for good health.

Who discovered cells, and how?

How are sol, solution and suspension different from each other?

What are the differences between the mass of an object and its weight?

What is the role of epidermis in plants?

What is the quantity which is measured by the area occupied below the velocity-time graph?

Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?

What do you mean by acceleration due to gravity?

Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur.

How is a prokaryotic cell different from a eukaryotic cell?

Define valency by taking examples of silicon and oxygen.