English Medium Class 9 - CBSE Question Bank Solutions for Science

What does the diffusion of gases tell us about their particles?

Give one example of diffusion of gases in a liquid.

Give reason for the following observation :

The smell of hot sizzling food reaches us even from a considerable distance but to get the smell from cold food, we have to go close to it.

Explain how, the smell of food being cooked in the kitchen reaches us even from a considerable distance.

Explain why, when a bottle of perfume is opened in a room, we can smell it even from a considerable distance.

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

Why do gases diffuse very fast?

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

Why does a gas exert pressure?

Why does a gas fill a vessel completely?

When a gas jar full of air is placed upside down on a gas jar full of bromine  vapours, the red-brown vapours of bromine from the lower jar go upward into the jar containing air. In this experiment :

When a gas jar containing colourless air is kept upside  down over a gas jar full of brown-coloured bromine vapour, then after some time, the brown colour of bromine vapour spreads into the upper gas jar making both the gas jars appear brown in colour. Which of the following conclusion obtained from these observations is incorrect?

The speed of a moving object is determined to be 0.06 m/s. This speed is equal to :

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.

Which of the following statement is correct regarding velocity and speed of a moving body?

Which of the following can sometimes be 'zero' for a moving body?
(i) average velocity
(ii) distance travelled
(iii) average speed
(iv) displacement

Which of the following could not be a unit of speed?

One of the following is not a vector quantity. This one is :

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.

A substance has neither a fixed shape nor a fixed volume. State whether it is a solid, a liquid or a gas.