STATE OF MATTER

STATES  OF  MATTER  AND  FORCES :

Water exists in three state i.e. solid (ice), liquid (portable water), gas (steam, vapors).

·       In these three states water has different physical properties but same chemical composition i.e. H₂O

·       Also characteristics of these states of water depend on the molecular energy and how molecules aggregate.

·       As molecules change its physical state (from liquid to gas, gas to liquid, solid to gas etc.) there is no change in chemical properties of the substance but some changes may occur in rate of chemical reaction.

Intermolecular Forces:

                             These are forces of attraction and/or repulsion between the interacting particles i.e. atom or molecules.

Dutch Scientist J. Van der Waals (1837-1923) explains deviation of the real gases from ideal behavior with intermolecular forces, so intermolecular forces are also called as van der waals forces.

Example: Hydrogen bonding which is strong dipole-dipole interaction.

Dispersion Forces: 

                             If an atom gets instantaneous dipole (i.e. Atom has more electron density in right or left hand side) then its nearby atom become induced dipole, so these two temporary dipole attract each other. This attraction force is known as dispersion forces.

·       As these forces were first proposed by F. London so these forces are also known as London forces.

Dipole-Dipole Forces: 

                                    This type of force act between the molecules which have permanent dipole. Dipole of these molecule possess some partial charges (denoted by delta  that is delta positive or delta negative)

Example: HCl molecule, where H possess delta positive and Cl possess delta negative.

Dipole-Induced Dipole Forces: 

                                             These attractive forces act between polar and non-polar molecules where polar molecules have permanent dipole, which induced the dipole and non-polar molecule by deforming electronic cloud of non-polar molecule.

·       As polarisability increases, strength of the attractive interaction also increases.

Hydrogen-Bond:  

                           It is a type of dipole-dipole interaction present in molecules with high polar N-H, O-H and H-F bonds.

Thermal Energy: 

                           It is the energy of the body arise due to the motion of its atoms and molecules.

·       Thermal energy is directly proportional to temperature of the substances.

Intermolecular forces v/s Thermal interactions

·       Intermolecular forces make molecules of the substance keep together.

·       While thermal energy of the substance make molecules keep apart.

·       These two (thermal energy and intermolecular forces) decides collectively the states of matter.

·       If intermolecular forces predominance then

                                      Gas->Liquid->Solid

·       If thermal energy predominance then

                                      Solid->Liquid->Gas

What is Troposphere: 

                                   It is the lowest layer of the atmosphere held to surface of the earth by gravitational forces where we live. It contains O₂, CO₂, N₂ and water vapors etc.

Gaseous State: 

                     Only 11 elements ( H, O, N, F, Cl, He ,Ne, Ar, Kr, Xe, Rn exists in gaseous state under normal conditions.

Characteristic Physical Properties Of Gases

·       Gases are highly compressible.

·       Gases exert the equal pressure in all direction.

·       As compared to solid and liquids, gases have much lower density.

·       Gases don’t have definite (fix) shape and volume.

·       Gases mix completely and evenly in all proportions.

The following table illustrates different states of matter and their physical properties.

	Property	States of matter
		Solid	Liquid	Gas(Vapor)
i)	Shape	definite	indefinite	indefinite
ii)	Volume	definite	definite	indefinite
iii)	Molecular Bonding	very strong	strong	Weak
iv)	Examples	NaCl ZnSO4	H2O Petrol	H2 , CO2 LPG

The Molecular mode of Solids, Liquids, Gases

Plasma : This is the fourth state of matter. It is a type of gas containing positively and negatively charged particles in approximately equal numbers and present in the sun and most stars.