Page 1 - 3. LESSON NOTES-INTERCONVERSION OF DIFFERENT STATES OF MATTER
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SAI International School
                                                       Class-IX

                                                Subject-Chemistry
                                      Topic-Matter in our surroundings
                        Sub topic- Interconversion of different states of matter

                                                  LESSON NOTES
               Change of State of Matter:
               Physical states of matter can be interconverted into each other by following two
               ways:
               1. By changing the temperature


               2. By changing the pressure


               1. Effect of Change of Temperature:
               (a)Solid to liquid:
            •  On increasing the temperature of solids, the kinetic energy of the particles increases
               which overcomes the forces of attraction between the particles thereby solid gets
               converted to a liquid.
            •  Melting: Change of solid state of a substance into liquid is called melting.
            •  Melting point: The temperature at which a solid melts to become a liquid at the
               atmospheric pressure is called its melting point.
                                        o
            •  Melting point of ice is 0 c.
               (b) Liquid to gas:
            •  On heating a liquid like water, the kinetic energy of its particles increases as high as
               in a gas, thus causing the liquid to change to a gas.
            •  Boiling: The change of a liquid substance into gas on heating is called boiling.
            •  Boiling point: The temperature at which a liquid boils and changes rapidly into a
               gas at the atmospheric pressure is called its boiling point.
                                            o
            •  Boiling point if water is 100 C.
               (c) Gas to liquid:
            •  On cooling a gas like steam (or water vapour), the kinetic energy of its particles is
               lowered down, causing them to move slowly and bringing them closer, forming a
               liquid.
            •  Condensation: The process, in which a gas, on cooling, turns into a liquid at a
               specific temperature is called condensation or liquefaction.
               (d) Liquid to solid:
            •  When a liquid is cooled down by lowering its temperature, its particles lose the
               kinetic energy and come to a stationary position, causing the liquid to turn to soilid.
            •  Freezing: The change of a liquid substance into soilid by lowering its temperature is
               called freezing.
            •  Freezing point: The temperature at which the state of a substance changes from a
               liquid to a solid is called the freezing point of that substance.
               (e) Solid to gas: Sublimation: The change of state of a substance directly from a
               solid to gas , without changing into the liquid state, is called sublimation.
               (f) Solid to gas: Deposition: The change of state of a substance directly from  gas
               to solid, without changing into the liquid state, is called deposition.



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