States of Matter Class 11 Notes PDF
States of Matter Class 11 Notes PDF
Gas is the state of matter in which molecules are always in random motion. Intermolecular interactions are extremely small (almost negligible) as compared to other states like solid and liquid. Gases are highly compressible states of matter and their state of diffusion is maximum. Gases have their own importance in the living world. Air is a gaseous mixture of oxygen, nitrogen, CO2, Ar, etc.
Intermolecular Forces
Intermolecular forces are the forces of attraction and repulsion between interacting particles. This term does not include the electrostatic forces that exist between the two oppositely charged ions.
Van der Waal’s Forces
These are the weak forces of attraction between two molecules with or without any strong bond. These are electrostatic in nature. Types of van der Waal’s forces are as follows:
1. Dipole-dipole interaction: These forces exist between two molecules that are polar in nature. Opposite charges of two dipoles attract each other and produce interactions called keesom forces. In HCl, dipole-dipole interactions exist.
The dipole-dipole interaction energy is inversely proportional to the sixth power of the distance between the rotating polar molecules.
2. Dipole-induced dipole interaction: When a polar molecule comes closer to a non-polar molecule it induces weak polarity (dipole) in that molecule. Now, weak interactions develop between polar molecules and molecules in which polarity is induced. These interactions are known as Debye interactions.
3. London dispersion forces: This polar molecule produces polarity in another molecule. Weak interaction arises between instantaneous dipoles. These interactions are known as Dispersion forces or London forces.
Measurable Properties of Gases
1. Temperature: Temperature is a relative measure or indication of hotness or coldness. At absolute zero on the Kelvin scale is equivalent to –273.15°C on the Celsius scale. Both the Celsius and the Kelvin scales have units of equal magnitude that are one degree Celsius equivalent to one kelvin.
Thus T(K) = T(°C) + 273.15
2. Pressure of a gas: According to laws of motion, pressure is defined as force applied per unit area of surface. It is denoted by P and the SI unit of it is Pascal (Pa). It is a scalar quantity.
3. Atmospheric Pressure: The atmospheric pressure at a point is equal to the weight of a column of air of a unit cross-sectional area extending from that point to the top of the atmosphere. Its value is 1.013 × 105 Pa at sea level. Atmospheric pressure is measured using an instrument called a barometer.
States of Matter Class 11 Notes PDF
Rest notes are available in the PDF attached
