NCERT SOLUTION CLASS 9 SCIENCE EXERCISE

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NCERT SOLUTION OF CHAPTER 1 OF CBSE BOARD CLASS 9 ( MATTER IN OUR SURROUNDINGS)

 EXERCISE  PAGE NO 12

QUESTION NO 1

     Convert the following temperatures to the celsius scale.
(a) 293 K           (b)   470 K

ANSWER 

  (a)  293 K = 293-273 = 20 degree centigrade
  (b) 470 K = 470-273 = 197 degree centigrade  

QUESTION NO 2

   Convert the following temperatures to the kelvin scale.
(a) 25 degree centigrade     
(b) 373 degree centigrade 

ANSWER    

(a) 25 degree centigrade =    25 + 273= 298 K
(b) 373 degree centigrade = 373+273 = 646 K

QUESTION NO 3 

     Give  reason for following observation observations.
(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.

ANSWER

 (a) Naphthalene balls has the property of sublimation. Evaporation of naphthalene balls takes place easily and it disappear with time without leaving any solid.

(b) Gaseous particle have less intermolecular force hence they move rapidly. So perfume diffuse in air easily. That's why we can smell perfume sitting several meters away.

QUESTION NO 4

    Arrange the following substances in increasing order of forces of attraction between the particles ----- water,sugar,oxygen

ANSWER

  Oxygen,water,sugar

QUESTION NO 5

  What is physical state of water at---
(a) 25 degree centigrade  (b)  0 degree centigrade  (c)  100 degree centigrade

ANSWER

  (a)  Liquid 
  (b) Solid and Liquid
  (c) Liquid and Vapour

QUESTION NO 6

     Give two reason  to justify--------

  (a)  Water at room temperature is a liquid.
  (b) An iron almirah is a solid at room temperature.

ANSWER --

  (a) Water at room temperature is a liquid because it has fluidity and
  (i) has definite volume 
  (ii) but no definite shape

  (b) An iron almirah is a solid at room temperature because
  (i) it is rigid
  (ii) and has a definite shape

QUESTION NO 7

 Why is ice at 273 K more effective in cooling than water at the same temperature?

ANSWER---

    Ice at 273 K is less energetic than water at same temperature. Because at this temperature water contains latent heat of fusion. So it has less cooling effect.

QUESTION NO 8 

   What produces more severe burns,boiling water or steam?

ANSWER----

 Steam produces more severe burns than boiling water. This is because of steam has more energy in he form of latent heat of vaporization.
  

QUESTION NO 9 


 Name A,B,C,D,E and F in the following diagram showing change in its state.

ANSWER----

 A-------   Melting
 B------- Boiling
 C------- Condensation
 D------- Solidification
 E------   Sublimation
 F------- Sublimation

  
   

     

     








   

  
    
     

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