Gaseous State

• It is the simplest form of matter.
• The cohesive force between molecules of a gas is negligible because of this, gas molecules are free to move randomly.

Some measurement parameters of gas:

1. Mass: Mass of gas is measured in terms of gram or kilograms.

2. Mole: It’s  not possible to count the numbers of particles present in definite amount of substances so, quantity of matter is expressed in terms of no. of moles. A mole is amount of substance which has mass equal to gram atomic weight/mass(if the substance is atomic) or gram molecular mass(if the substance is molecular). Mole is denoted by ' n'. Its SI unit is Mol. 1 mole of substance contains 6.023*10²³ is called Avogadro’s number( N)

For example,
Atomic mass of carbon=12 gm=1 mole of carbon=6.023 ×10²³ no. of carbon atoms.
Atomic mass of sodium=23 gm= 1mole of Na= 6.023×10²³ no. of Na atoms.

3. Molar mass: Mass of one mole of substance is called molar mass. It’s unit is g/mol, kg/mol.

5. Volume: Volume is the space occupied by a body. Gas doesn’t have definite volume. Gas occupies whole volume of container in which it is kept so volume of gas is volume of container at NTP( Normal Temperature Pressure)

6. Temperature: Temperature of gas is measured in degree celcius(°C). During calculation, degree  Celsius is converted into absolute or degree Kelvin by using following relation:

7. Pressure: When gas molecules collide with each other or on the wall of container, pressure is exerted. The force exerted by gas molecules per unit area on the wall of container or on the surface where the molecules collide is called gas pressure. The pressure exerted by atmospheric air on the surface of Earth is called atmospheric pressure.