question_answer

Taking one example, show the experiment of process of sublimation. OR (i) Define boiling point. (ii) Express the boiling point of water in Celsius as well as well as Kelvin scale. (iii) How will you show the presence of water vapors in air? (iv) Give the full forms of (a) LPG (b) CNG. (v) Why evaporation is called surface phenomenon?  

Answer:

Take some ammonium chloride in a China dish.                                                                                                                                                                         (2) Put an inverted funnel over the China dish. Cover the steam of funnel by a cotton plug. Now heat the dish slowly. Observation Ammonium chloride change its state from solid to vapours directly without going through liquid state. (2)                    Inference The change of state directly from solid to gas without changing in liquid state (or vice versa) is called  sublimation.                                                                                                                                                                                                            (1) OR (i) Boiling point of a liquid is that fixed temperature at which that liquid changes into gaseous state rapidly.          (1) (ii) Boiling point of water is 100° C or 373° K.                                                                                                                                         (1) (iii) Anhydrous calcium chloride turns wet on keeping exposed to air.                                                                     (1) (iv)(a)LPG Liquefied Petroleum Gas (b) CNG Compressed Natural Gas                                                                                                                                                            (1) (v) Since evaporation occurs only from the surface of liquid.                                                                                                        (1)