Thursday, May 19, 2011

9th Chemistry Test Paper solved for Ch: Matter in our surrounding CBSE

Chapter 1: Matter in Our Surroundings  Class IX, CBSE TEST PAPER-02    
1. If you decrease the surface area and increase the temperature, then the rate of evaporation
(a) Increase (b) decrease (c) remain same  (d) may increase or decrease depending upon other factors                     
2. 300k will have its corresponding temperature in degree centigrade as:-
(a) 300c (b) 3000c (c) 270c (d) 6730c        
3. Liquid to gas and gas to liquid changes are called:-
(a) vaporization and condensation                        (b) condensation and vaporization
(c) sublimation and condensation                        (d) condensation and sublimation 
4. Physical state of water at 250c, 00c and 1000c is respectively
(a) liquid, solid and gas                                       (b) solid, liquid and gas
(c) solid, gas and liquid                                       (d) gas, solid and liquid  
5. What happens when the temperature of the solids increase ?
6. When heat is being supplied to a solid, then what does the heat energy do to the particles of solid?
7. Why is it that on increasing the wind speed the rate of evaporation increases ?
8. Why do we say that evaporation is a surface phenomenon?                
9. What is the state of inter particle distance inside a solid, liquid and gas?                 
10. Why it is that to smell cold food, we have to go close but smell of hot food reaches us several meters away?    
11. Why is it that a wooden chair should be called a solid and not a liquid?                    
12. Give an experiment to show that ammonium chloride undergoes sublimation.            
(Matter in our surrounding) [ANSWERS]
Ans 01. (c)         Ans 02. (c)         Ans 03. (a)         Ans 04. (a)
Ans 05. When temperature of the solid is increased, kinetic energy of the particles increases as results particles vibrates more freely with greater speed. They overcome the force of attraction between the particles and start moving more freely.
Ans06. The heat supplied to the solid, helps the particles to overcome the forces of attraction between them and increases their kinetic energy, as a result of which particle break free the forces of attraction and changes to liquid state.
Ans07. When the speed of wind increases, then they blow away with them the water vapour in the air and as results evaporation will increase because the surrounding air will be able to receive more vapours and hence evaporation increases.
Ans 08. Evaporation is called a surface phenomenon because only particles of the surface of liquid gains energy and changes into vapors.
Ans09. In solids, the particles are very close to each other and are bonded by strong forces of attraction so inter particle distance is least.

In liquid, the particles are far away from each other and are bonded by weak forces of attraction, so inter particle distance is large.

 In gases, particles are very far apart from each other and are bonded by very weak forces of attraction so, inter particle distance is a largest.
Ans10. In hot food, the particles are at high temperature so quickly changes to vapour and hence the vapours have greater kinetic energy so travel faster and travel to far off distances. Whereas in cold food, because of temperature being low, particles do not change to vapour state and hence cannot travel faster so the smell does not reaches to a

Person sitting far away.
Ans11. A wooden chair should be called a solid not a liquid because the particles of wooden chair are very close to each other, it has negligible compressibility and it maintains its shape when subjective to outside force.
Ans12. Experiment to show that ammonium chloride (NH4Cl ) undergoes sublimation:-

(a) Take an inverted funnel and inside it china dish with crystal of ammonium chloride (NH4Cl).

(b) Heat the crystals with the help of a burner.

(c) As soon as the crystal is heated, we observe the vapors of NH4Cl and the solidified Ammonium chloride (NH4Cl) along the walls at the upper end of the beaker.

(d) This shows that solid ammonium chloride does not undergo liquid state but directly changes to vapour state which them solidifies i.e. it undergoes sublimation (solid changes directly to gases without undergoing liquid state).
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