Class 9 Science - Chapter Natural Resources NCERT Solutions | What are the different states in which w

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

Why is the atmosphere essential for life?

What causes winds?

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?

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

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

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?

What are the differences between amphibians and reptiles?

Distinguish between speed and velocity.

A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity.

Give the names of the elements present in the following compounds.

(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.

Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?

Why does a block of plastic released under water come up to the surface of water?

What do you mean by acceleration due to gravity?

How many atoms are present in a

(i) H₂S molecule and
(ii) PO₄^3- ion?

Are the answers to the above questions necessarily the same or different? Why?

Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?