# Chemistry: States of Matter: Intermolecular Interaction and its Types and General Behavior of gases-the gas laws

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## The Three States of Matter

• Solid, Liquid and Gas are the three distinct physical forms of matter.

• All the three states of matter are made up of small tiny particles with a particular mass and can occupy space.

• Solid consists of tightly packed particles; the particles are not free to move around.

• Liquid is the state of matter with a definite volume but no fixed shape. In liquid the molecules are free to move around and are loosely packed as compared to the solids.

• Gas as a state of matter is defined as the one with no fixed shape and no fixed volume. The molecules in gas are very loosely packed and are free to move around.

## Intermolecular Interaction and Its Types

• Intermolecular interactions occur between all types of molecules or ions in all states of matter.

• Liquids have less intermolecular forces then solid but higher than gases.

• There are three major types of intermolecular forces: London dispersion force, dipole-dipole interaction, and ion-dipole interaction.

## General Behavior of Gases-The Gas Laws

• The gas laws consist of three primary laws: Charles’ Law, Boyle’s Law and Avogadro’s Law.

• According to Boyle’s law, if the temperature of a gas is held constant, increasing the volume of the gas decreases its pressure.

• Avogadro’s law is a gas law that relates to the volume of a gas to the amount of substance of gas present. It is an experimental gas law.

## Ideal Gas Equation

• If we combine the Boyle’s law, Charle’s law and Avogadro’s law, we get an equation and V/T=k, PV/T=constant, the ideal gas equation obtained is where P= pressure of the gas; V=volume of the gas; n= Number of Moles; T=Absolute temperature; R=Ideal Gas constant also known as Boltzmann Constant = 0.082057 L atm

• It is possible to study any gas using equation under the assumptions of Standard Temperature and Pressure i.e. STP.

## Dalton’S Law of Partial Pressure

• The Sum of the partial pressures of the component gases is equal to the total pressure of a mixture of gases. Pressure Total = Pressure Gas 1 + Pressure Gas 2 + Pressure Gas 3 + ...

• The total pressure of a mixture of gases can be defined as the sum of the pressures of each individual gas:

• The partial pressure of an individual gas is equal to the total pressure multiplied by the mole fraction of that gas.

• Dalton’s law allows us to calculate the total pressure in a system from each gas individual contribution.

## Kinetic Molecular Theory of Gases

• The average kinetic energy of a collection of gas particles is directly proportional to absolute temperature only.

• This theory also states that gas particles are in constant motion and exhibit perfectly elastic collisions.

## Kinetic Energy and URms

• The energy that an object or body possesses by virtue of its motion is called the kinetic energy. For e.g. person walking, a thrown flying disc etc.

• The root means square velocity (RMS velocity) is a way to find a single velocity value for the particles. The average velocity of gas particles is found using the root mean square velocity formula.