CLASS-9                          MATTER IN OUR SURROUNDINGS
                                                 WORKSHEET

1. A gas jar containing  air is inverted over another jar containing NO2 gas which is brown in colour and heavier than air.After some time brown colour is seen in the inverted glass jar too. Identify the phenomenon associated with the observation.

2.A spoonful of sugar is added to a beaker containing  500 ml water of water and stirred for  a while. State any two observation that you will make.Account for your observations

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3.In which of the following substances the inter molecular forces are the (a) weakest (b) strongest

 Water, Alcohol,Carbon- di- oxide, sodium chloride

4.Give reasons-

(a) Gas fills the vessel completely in which it is kept.

(b) A gas exerts pressure n the walls of the container.
 (c) Gases have high compressibility and show diffusion.

5. How would you confirm that colourless liquid given to you is pure water?

6.Explain one example of diffusion of solid into another solid. 

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

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8.In a beam of sunlight entering  a room , we can sometimes see dust particles moving in a haphazard way in the air. Why do they move?

9.Honey is more viscous than water. Why?

10.Bromine and air takes 15 minutes to diffuse but bromine diffuses in vaccum very rapidly. Why is this so?

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