IX SCIENCE ASSIGNMENT: MATTER AROUND US

1.            [3] (a)     Define  evaporation.                                                                                                         

 (b)     How  increase  in surface  area  affects  rate  of evaporation with  an example.

2.            Define  the following terms.  
         (a)     Latent  heat  of fusion   (b)     Sublimation   (c)     Evaporation

3.         [2] Show  by an activity  that  the gases  are highly  compressible as compared to solids  and  liquids.

4.           [2] Convert the  following temperatures to                                                                                     

(a)     Celsius  scale                    (i)      313 K                    (ii)     370 K

(b)     Kelvin  scale                     (i)      23°  C                     (ii)     73°  C

5.           [3] (a)     What  is meant by evaporation ?                                                                                              

(b)     Define  latent  heat  of fusion.

(c)     Why  should the wet  clothes  be spread out  while  drying ?

6.           [3] With the help  of a diagram explain  in brief an activity  to show  that  particles of matter are very  small.

7.           [1]At what  temperature does  solid  ice and  liquid  water  co - exist together ?                              

8.           [2]What  is the effect of the following on the rate  of diffusion ?                                                    

(a)     temperature                                   (b)     density of liquid

9.           [5] (a)   Define matter. Name the state of matter in which the forces between the constituent particles are  

(i) Strongest, (ii) Weakest.

(b)   Give reasons for the following :                                                                                               

(i)    A liquid generally flows easily.

(ii)   Ice at 0°C appears colder  to the  mouth than  water at 0°C. Why ?

(iii)  Doctors  advise to put  strips  of wet cloth on the forehead of a person having high  temperature.

10.        [5] Account for the  following

(a)   For any physical state, the temperature remains constant during the change of state.

(b)   Water  kept  in an earthen pot  becomes  cool in summer.

(c)   We are able to sip hot tea from  a saucer  rather than  a cup.

(d)   An iron rod  is solid  at room  temperature.

(e)    When sugar crystals dissolve in water, the level of water does not rise appreciably.

11.        [2]Why  should we wear  cotton  clothes  during summer  ?                                                                

12.        [3] Describe  an activity  to show  that  matter is made up  of small  particles.                              

13.        [3] Answer the  following questions.                                                                                      

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

(b)   Name  the  two  gases  which  are  supplied in  compressed form  in  homes  and hospitals.

(c)   What  is dry  ice ?

14.        [3]Explain  any  three  factors  which  affect the  rate  of evaporation.                                            

15.        [3]Give reasons :                                                                                                                                        

(a)     Water  kept  in an earthen pot  becomes  cool after  some  time.

(b)     Ice at 0^oC is more  effective  in cooling  than  water at 0^oC.