STATES OF MATTER INTRODUCTION
Based on the physical property of matter these can be classified into solids, liquids, and gases. Solids have a definite volume and shape liquids have a definite volume but indefinite shape while gases neither have a fixed volume nor a fixed shape. All the three physical states of the matter occur due to the accumulation of the molecules in different states.
The physical state of matter is determined by intermolecular forces, molecular interaction and the effect of thermal energy on the motion of the particle.
- INTERMOLECULAR FORCES AND IT’S TYPES
- GASEOUS LAWS
- IDEAL GAS EQUATION
- DALTON’S LAW OF PARTIAL PRESSURE
- KINETIC MOLECULAR THEORY OF GASES
- VAN DER WALLS EQUATION
- IMPORTANT NCERT DEFINITIONS
The force of attraction and repulsion between the interacting particle is called intermolecular forces.
It is different from the electrostatic forces between the oppositely charged ions that holds them together. It is also different from the covalent bond.
These force can be of following types:
- DISPERSIVE FORCES: It is the force of attraction between the two non-polar molecules. It takes place due to instantaneous dipole. These forces are weakest amongst all the interactive forces.
- DIPOLE-DIPOLE INTERACTION: These forces act between the molecules possessing a permanent dipole. The ends of the dipole possess partial charges which are always less than the charge of 1e.
- DIPOLE-INDUCED DIPOLE: This type of interaction takes place between the molecules having permanent dipole and a non-polar molecule. When a non-polar molecule comes in contact with a polar particle, a polarity is induced in it. It is called an induced dipole.
- HYDROGEN BOND: It is the special case of dipole-dipole interaction. It takes place between a positively charged hydrogen-bonded covalently with a high electro negatively. This type of interaction force is the strongest amongst all other interaction forces.
- ION DIPOLE INTERACTION: The force of attraction between an ion and the opposite charge ends of a polar molecule is called ion-dipole interaction.
- ION INDUCED DIPOLE INTERACTION: This type of interaction takes place when a non-polar molecule comes in contact with an ion and becomes polar. Such kind of interaction is called ion-induced dipole interaction.
1. BOYLE’S LAW: At constant temperature the pressure of the fixed amount of gas is inversely proportional to its volume.
The graph drawn between the pressure and volume of the fixed amount of a gas at constant temperature is called an isotherm
2. CHARLES LAW: At constant pressure the volume of a fixed amount of a gas is directly proportional to its absolute temperature.
3. GAY LUSSAC’S LAW: At constant volume, the pressure of a fixed amount of gas is directly proportional to its temperature
4. AVAGADRO’S LAW: At constant temperature and pressure, the volume of gases is directly proportional to its amount
IDEAL GAS EQUATION
A gas that follows all the gaseous laws is called an ideal gas. An ideal gas can be explained by a single equation called the ideal gas equation.
DALTON’S LAW OF PARTIAL PRESSURE
According to this law-at constant temperature the total pressure exerted by the mixture of a gas which is non reacting in nature is equal to the sum of their partial pressure.
Let P is the total pressure exerted by the mixture of 4 non reacting gases and having their partial pressure as P1, P2 , P 3 and P4 respectively then acc to Daltons law
P= P1+P2 +P 3 +P4
KINETIC MOLECULAR THEORY OF GASES
According to this theory:
- Every gas made up of very small identical particles called atoms and molecules.
- The size of these particles is very small as compared to the distance between them.
- The volume of these particles is also very small as compared to the volume occupied by gas that it can be neglected.
- The intermolecular force between the particles of gas is also negligible therefore they can freely move constantly in all the directions.
- While moving they keep on colliding with each other and also with the walls of vessels in which they are kept.
- These collisions are perfectly elastic that is the total energy of the particles before and after the collision remains to conserve.
- Due to these collisions the gases apply the pressure on the walls container.
- Different particles of a gas may have different kinetic energy at some time.
- The average kinetic energy of the particles of a gas is directly proportional to temperature.
VAN DER WAALS EQUATION
Real gas show deviation from ideal gas law because molecules interact with each other. At high-pressure molecules of gases are very close to each other. Molecular interaction starts operating.
At high-pressure molecules do not strike the walls of the container with full impact because these are dragged attractive forces. This affects the pressure exerted by the molecules on the walls of the container.
Repulsive forces also become significant. Repulsive interaction is short-range interaction and is significant when molecules are in contact.
The volume occupied by the molecules also become significant because instead of moving in volume V, these are now restricted to volume (V-nb). The equation is –
IMPORTANT DEFINITIONS IN STATES OF MATTER-
States of matter include several more parts. Now we are going to discuss several important definition from class 11 ncert states of matter important book definition-
- COMPRESSIBILITY FACTORY- the ratio between PV and nRT is called the compressibility factor (Z).
- BOYLE’S TEMPERATURE- the temperature at which a real gas behaves like an ideal gas over a long range of pressure is called its Boyle’s temperature.
- CRITICAL TEMPERATURE- the temperature above which a gas can’t be liquefied on applying pressure is called its critical temperature.
- Vapor PRESSURE- at a constant temperature the pressure applied by the vapor of a liquid on the walls of a container at liquid-vapor equilibrium is called its vapor pressure.
- CRITICAL PRESSURE- the minimum pressure required to liquefy a gas at its critical temperature is called its critical pressure
- CRITICAL VOLUME- the volume occupied by one mole of a gas at its critical temperature is called its critical volume.
- SURFACE TENSION- The force acting at the right angle to the surface along a 1 cm length of a surface is called surface tension.
- SURFACE ENERGY- It is the work done in erg require to be done to increase 1 cm sq area of a liquid.
- VISCOSITY- The force that opposes the relative motion in the layers of a liquid is called viscous force and this property is called viscosity. The viscous force occurs due to the intermolecular force of attraction between the molecules of different layers of the liquid.