Give reasons:- A gas exerts pressure on the walls of the container. - Science


Give reasons:-

A gas exerts pressure on the walls of the container.


Solution 1

Particles of gas move randomly in all directions at high speed. As a result, theparticles hit each other and also hit the walls of the container with a force. Therefore, gas exerts pressure on the walls of the container.

Solution 2

A gas exerts pressure on the walls of the container because the molecules of the gas are in constant random motion due to high kinetic energy. These molecules constantly vibrate, move and hit the walls of the container thereby exerting pressure on it.

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Chapter 1: Matter in Our Surroundings - Intext Questions [Page 6]


NCERT Science Class 9
Chapter 1 Matter in Our Surroundings
Intext Questions | Q 3.2 | Page 6


The mass per unit volume of a substance is called density (density = mass/volume). Arrange the following in order of increasing density − air, exhaust from chimney, honey, water, chalk, cotton, and iron.

Which of the two diffuses faster : a liquid or a gas?

A bottle of perfume was opened in a room. The smell of its vapours spread in the entire room. Name the property of gases which is responsible for this behaviour of perfume vapours.

Why do gases have neither a fixed shape nor a fixed volume?

Explain why, diffusion occurs more quickly in a gas than in a liquid.

Name two gases of air which dissolve in water by diffusion. What is the importance of this process in nature?

Look at the diagram on the right side. Jar A contains a red-brown gas whereas jar B contains a colourless gas. The two gas jars are separated by a galas plate placed between them

  1. What will happen when the glass plate between the two jars is pulled away?
  2. What name is given to the phenomenon which takes place?
  3. Name the brown gas which could be in jar A.
  4. Which is the colourless gas most likely to be present in jar B?
  5. Name one coloured solid and one colourless liquid which can show the same phenomenon.

A student placed a gas jar containing air in the upside down position over a gas jar full of red-brown bromine vapours. He observed that the red-brown colour spread upwards into the jar containing air. Based on this observation, the student concluded that it is only the bromine vapour which moves up and diffuses into air in the upper jar, the air from the upper jar does not move down by diffusion into the lower jar containing bromine vapours. Do you agree with this conclusion of the student? Give reason for your answer.

Why do gases not have fixed shape?

The space between ______ particles is the greatest one.

______ is not affected by gravity.

How does the substance of gaseous particles change to a liquid state?

Comment upon the following:-

filling a gas container

Comment upon the following:-


Which of the following is false for gases?

Explain why?

  1. A gas fills a vessel completely?
  2. Camphor disappears without leaving any residue.

Which of the following is TRUE about gaseous state?

Fig. I Fig. II

In figure-I, an air column of length ℓ1 is entrapped by a column of Hg of length 8 cm. In figure-II length of same air column at the same temperature is ℓ2. The `ℓ_1/ℓ_2` is:
(1 atm = 76 cm of Hg)

2 litre He gas at 2 atm and 300 K is inserted into a 4 litre rigid container containing N2 at 600 K and 4 atm. Finally mixture is maintained at 600 K temperature. The final pressure of gaseous mixture would be ______ torr.

Two gases A and B having molecular weights 60 and 45 respectively are enclosed in a vessel. The wt. of A is 0.50 g and that of B is 0.2 g. The total pressure of the mixture is 750 mm. The partial pressure of the gases B is ______ mm Hg.

A gaseous mixture of He and O2 is found to have a density of 0.518 gL-1 at 25° C and 720 torr. The mass percent of helium in this mixture is ______.


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