EXERCISES (Text book)

EXERCISES: ( Text book)

1: Convert the following temperatures into the Celsius scale.

(a) 300 K                              (b) 573 K
Ans: (a) 300 K  =  300 – 273  =  27^o C                                                                                                           
(b) 573 K  =  573 – 273    =  300^o C

2: Convert the following temperatures into the Kelvin scale.

(a) 25^°C                             (b) 373^°C
Ans:  (a) 25^°C  =  25 + 273  =  298 K                                                                                                               
(b) 373^°C  =  373 + 273  =  646 K

3: Give reasons for the following observations.

(a) Naphthalene balls disappear with time without leaving any solid.                                                
Ans: Naphthalene shows the property of sublimation. Evaporation of naphthalene takes place easily and so it disappears during course of time without leaving a solid.

(b) We can get the smell of perfume sitting several meters away.                                                         
Ans: The vapours of the highly volatile liquid present in the perfume diffuse quickly and reaches us sitting several meters away

4: Arrange the following in increasing order of forces of attraction between the particles               water, sugar, oxygen.                                                                                         
Ans: Oxygen < Water < Sugar.

5: What is the physical state of water at —

(a) 25°C                         (b) 0°C                                                (c) 100°C.                                                   
Ans: (a) Liquid           (b) Solid and Liquid                         (c) Liquid and Vapours

6: Give two reasons to justify:

(a): Water at room temperature is a liquid.                                                                                                
Ans : Water at room temperature is a liquid because                                                                                 
(i) It has fluidity and has definite volume but no definite shape.                                                             
(ii) Water flows from higher level to lower level.                                                                                         
(b): An iron almirah is a solid at room temperature.                                                                                
Ans : An iron almirah is a solid at room temperature because it is rigid , has a definite shape and it has a  fixed volume.

7: Why is ice at 273 K more effective in cooling than water at the same temperature.
Ans : Ice at 273 K is less energetic than water  because of the difference in the latent heat of fusion which is present in water at the same temperature in the form of extra energy.

8: What produces more severe burns, boiling water or steam.                                         
Ans: Steam produces more severe burns than boiling water. This is because steam has more kinetic energy than boiling water, present in it in the form of latent heat of vaporization.

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

Ans: A → Melting B → Boiling C → Condensation D → Solidification E → Sublimation F→Solidification of vapours.