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ICSE class 9 Chemistry, Study Of GAS LAWS



ICSE Class 9 chemistry Syllabus ( Study of Gas Law)

  1. The Behaviour of gases under changes of Temperature and pressure.
  2. Boyel’s law and Charles law
  3. Absolute zero
  4. Gas equation
  5. Relationship between kelvin scale & celsius Scale
  6. NTP/STP

Physical characteristics of gaseous State:

  1. Gases don’t have a specific shape. They acquire the shape of the container.
  2. Gases do not have a definite volume , It can change by changing the temperature and pressure.
  3. Gases always form a homogeneous mixture irrespective of their nature. Example: Air is a homogeneous mixture of different gases.
  4. Gases rapidly diffuse which means that they readily mix with one another.
  5. Gases are highly compressible and their volume decreases by increasing the pressure and vice versa.
  6. Gases exert pressure equally in all the direction.
  7. Gases have low density and are lighter than liquids and solids.
  8.  Measurable properties of Gas:

Mass of Gas: Determine by Direct weighting.

  1. Procedure: The container containing the gas is weighed and then the gas is then completely removed and the empty container is again weighted. The difference between the Two mass given the mass of the gas.
  2. Unite of Mass: In S.I unit is Kilogram (Kg), However The Mass of the gas is also expressed in grams (g).     1 kilogram = 103 gm
  3. Volume of the Gas: The Volume of the gas is the same as that of the container. Volume of the gas is the same as that of the container.
  4. Unit: In SI Unit of volume cubic meter (m3).  But smaller units such as Cubic decimeter ( dm3 and Cubic centimeter (cm3) are also common.Remember  1 m3 = 103 dm3 = 106 cm3

    In addition volume of gas is expressed in liters (L)

    1L = 103 mL = 103 cm3 = 1dm3

  5. Pressure of the Gas: A gas exerts uniform pressure in all the direction of an enclosed container.So pressure of the gas =

    ( Force the gas molecule exerted on the wall of the closed Container)/( Surface area of the container

  6. Measurement of Atmospheric Pressure: At sea level , The height of the mercury column inside the tube is 76 cm or 760 mm at 273 k and it corresponds to a pressure of 1 atmosphere
  7. NTP/STP: The volume of a gas changes with the change in temperature and pressure. In order to compare the volume of the gases, normal conditions of temperature and pressure (N.T.P) are employed.

    Normal Pressure: 1 atm or 760mm or 760 torr or 101.325 KPa

    Normal Temperature: 00 C or 273.15 K ( SI Unit)

    Writer Identity: Mr S.Halder is a well-known Chemistry faculty of Aims . He hold Bachelor of Civil engineering & Master of Civil Engineering  from Jadavpur University, He also did MBA (F) and A Chartered Engineer from Institute of Engineers (I). To contact the author please call Aims: +917003557150,+918697234172,+919748932154 Or Email : or log in:

    Aims: India’s Best Institute of JEE Main & advanced & NEET

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