Solid State Chemistry Class 12 CBSE

In  this course, we will discuss complete chapter named Solid State  Chemistry of Class 12 Chemistry. we will discuss each and every topic  important from CBSE point of view. This  course is designed in a very easy to understand format using 3D visual  animations which boost your learning and help you understand and  visualize difficult topics easily

INTRODUCTION:

Three states of matter are solid, liquid and gas. Amongst them liquid and gases are called fluids because  of their ability to flow. But solid cannot flow. The reason for that is  particles in solid are not free to move in available space. There is  strong intermolecular force of attraction in between the particles in  solid. The constituents particles in solid have fixed position and can  only oscillate about their mean position.  This gives the rigidity to  the solid and hence a fixed shape also. In brief we can say that:

“Solid state of matter possesses fixed mass, volume, shape and rigidity “.

Solids are classified on the basis of arrangement of constituent  particles. Due to their specific arrangements, it shows wide range of  properties and hence varied applications like as superconductors,  magnetic materials, polymers etc.

GENERAL CHARACTERISTICS OF SOLID STATE:

In nature the particular state of matter is governed by two opposing  forces at given set of temperature and pressure. These forces are  intermolecular force of attraction and thermal energy. If intermolecular  force of attraction is high as compared to thermal energy, particles  remains in closest position and hence very less movement in particles is  observed. In this case solid state is the preferred state of matter.

Let us revise the general characteristics of solid:

i) Fixed mass, volume and shape

ii) Strong intermolecular force of attraction

iii) Least intermolecular space

iv) Fixed position of constituent particles

v) Incompressible and rigid

CLASSIFICATION OF SOLIDS:

Solids are classified on the basis of arrangement of their  constituent particles. If the arrangement of constituent particles is  same throughout the solid (long range order) it is called crystalline. If the arrangement of particles does not follow any regular pattern throughout the solid (short range order) it is called amorphous solid.

Characteristics of crystalline solid:

• It consists of large number of small crystals having a definite geometrical shape.
• The arrangement of constituent particles is regular throughout the  solid (long range order). That is a fixed pattern of constituent  particles repeat itself periodically over the entire range of solid.
• They have sharp melting points.
• They are anisotropic in nature.

Anisotropy is defined as” Difference in properties when measured along different axes or different directions”.

Crystalline solid show different values of some of the physical  properties like electrical resistance, refractive index etc.when  measured along the different directions. The anisotropy arises due to  the different arrangement of particles in different directions.

Characteristics of amorphous solid:

• The arrangement of constituent particles is irregular throughout  the solid. Regular pattern of constituent particle is visible in small  areas only. That is it shows short-range order.
• Melting point is not sharp. Amorphous solid melts over a range of temperature.
• They have tendency to flow at slower rate.
• They are isotropic in nature.

“Isotropic means no difference in properties taken from any direction.”

Intext Questions:

Q.1 Classify the following solids as crystalline and amorphous.

Sodium chloride, quartz glass, quartz, rubber, polyvinyl chloride, Teflon

A.1 Crystalline solid: Sodium chloride, Quartz

Amorphous solid: Quartz glass, rubber, polyvinyl chloride, Teflon.

Q.2 why glass is considered as super cooled liquid?

A.2 Glass shows the tendency to flow at slower rate like liquid. Hence they considered as super cooled liquid.

Q.3 why the window glass of old buildings show milky appearance with time?

A.3 Glass is an amorphous solid. Amorphous solid has  the tendency to develop some crystalline character on heating. Due to  heating in day over the number of years, glass acquires some crystalline  character and show milky appearance.

Q.4 why the glass panes fixed to window or doors of old building become slightly thicker at bottom?

A.4 Glass is super cooled liquid. It has the  tendency to flow down very slowly. Due to this glass pane becomes  thicker at the bottom over the time.

Q.5 Sodium chloride is a crystalline solid. It shows  the same value of refractive index along all the direction.  True/False.  Give reason.

A.5 False

Crystalline solid shows anisotropy in properties. That is, it shows  different values for the given physical property in different direction.  All the crystalline solids show anisotropy in refractive index.  Therefore sodium chloride will show different values of refractive index  on different directions.

Q.6 Crystalline solid are anisotropic in nature. What does this statement means?[CBSE 2011]

A.6 Anisotropy is defined as” Difference in  properties when measured along different axis or from different  directions”. Crystalline solid show different values of some of the  physical properties like electrical resistance, refractive index  etc.when measured along the different directions. The anisotropy in  crystalline solid arises due to the different arrangement of particles  in different directions.

CLASSIFICATION OF CRYSTALLINE SOLIDS:

Crystalline solid can be classified on the basis constituent  particles and intermolecular force of attraction in between them.  Constituent particles are molecules, ions, metal kernel in sea of  electrons and atoms. Force of attraction operate in between the  particles are dispersion force, dipole-dipole interaction, hydrogen  bonding, electrostatic attraction, metallic bonding and covalent  bonding.