NCERT Class 12 Chemistry The Solid State

Read and download NCERT Class 12 Chemistry The Solid State chapter in NCERT book for Class 12 Chemistry. You can download latest NCERT eBooks for 2021 chapter wise in PDF format free from Studiestoday.com. This Chemistry textbook for Class 12 is designed by NCERT and is very useful for students. Please also refer to the NCERT solutions for Class 12 Chemistry to understand the answers of the exercise questions given at the end of this chapter

 

We are mostly surrounded by solids and we use them more often than liquids and gases. For different applications we need solids with widely different properties. These properties depend upon the nature of constituent particles and the binding forces operating between them. Therefore, study of the structure of solids is important. The correlation between structure and properties helps in discovering new solid materials with desired properties like high temperature superconductors, magnetic materials, biodegradable polymers for packaging, biocompliant solids for surgical implants, etc. From our earlier studies, we know that liquids and gases are called fluids because of their ability to flow. The fluidity in both of these states is due to the fact that the molecules are free to move about. On the contrary, the constituent particles in solids have fixed positions and can only oscillate about their mean positions. This explains the rigidity in solids. In crystalline solids, the constituent particles are arranged in regular patterns. In this Unit, we shall discuss different possible arrangements of particles resulting in several types of structures. The correlation between the nature of interactions within the constituent particles and several properties of solids will also be explored. How these properties get modified due to the structural imperfections or by the presence of impurities in minute amounts would also be discussed.

General Characteristics of Solid State

In Class XI you have learnt that matter can exist in three states namely, solid, liquid and gas. Under a given set of conditions of temperature and pressure, which of these would be the most stable state of a given substance depends upon the net effect of two opposing factors. Intermolecular forces tend to keep the molecules (or atoms or ions) closer, whereas thermal energy tends to keep them apart by making them move faster. At sufficiently low temperature, the thermal energy is low and intermolecular forces bring them so close that they cling to one another and occupy fixed positions. These can still oscillate about their mean positions and the substance exists in solid state. The following are the characteristic properties of the solid state:
(i) They have definite mass, volume and shape.
(ii) Intermolecular distances are short.
(iii) Intermolecular forces are strong.
(iv) Their constituent particles (atoms, molecules or ions) have fixed positions and can only oscillate about their mean positions.
(v) They are incompressible and rigid.

Amorphous and Crystalline Solids

Solids can be classified as crystalline or amorphous on the basis of the nature of order present in the arrangement of their constituent particles. A crystalline solid usually consists of a large number of small crystals, each of them having a definite characteristic geometrical shape. In a crystal, the arrangement of constituent particles (atoms, molecules or ions) is ordered. It has long range order which means that there is a regular pattern of arrangement of particles which repeats itself periodically over the entire crystal. Sodium chloride and quartz are typical examples of crystalline solids. An amorphous solid (Greek amorphos = no form) consists of particles
of irregular shape. The arrangement of constituent particles (atoms, molecules or ions) in such a solid has only short range order.

Exercises

1.1 Define the term 'amorphous'. Give a few examples of amorphous solids.
1.2 What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?
1.3 Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous.
(i) Tetra phosphorus decoxide (P4O10)   (vii) Graphite
(ii) Ammonium phosphate (NH4)3PO4    (viii) Brass
(iii) SiC     (ix) Rb
(iv) I2       (x) LiBr
(v) P4       (xi) Si
(vi) Plastic
1.4 (i) What is meant by the term 'coordination number'?
     (ii) What is the coordination number of atoms:
          (a) in a cubic close-packed structure?
          (b) in a body-centred cubic structure?
1.5 How can you determine the atomic mass of an unknown metal if you know its density and the dimension of its unit cell? Explain.
1.6 'Stability of a crystal is reflected in the magnitude of its melting points'.

1.7 How will you distinguish between the following pairs of terms:
(i) Hexagonal close-packing and cubic close-packing?
(ii) Crystal lattice and unit cell?
(iii) Tetrahedral void and octahedral void?
1.8 How many lattice points are there in one unit cell of each of the following lattice?
(i) Face-centred cubic
(ii) Face-centred tetragonal
(iii) Body-centred
1.9 Explain
(i) The basis of similarities and differences between metallic and ionic crystals.
(ii) Ionic solids are hard and brittle.
1.10 Calculate the efficiency of packing in case of a metal crystal for
(i) simple cubic
(ii) body-centred cubic
(iii) face-centred cubic (with the assumptions that atoms are touching each other).

Please refer to attached file for NCERT Class 12 Chemistry The Solid State

Tags: 

 


Click for more Chemistry Study Material

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

FAQs on Policy for Tabulation of Marks for Class 10 Board Exams

ON POLICY Question.1 How CBSE will declare the result of Class-X? Answer. Results of Class X Board will be declared on the basis of an objective criterion developed by the Board vide Notification no.CBSE/CE/2021 dated 01.05.2021. Question.2. If any candidate is not...

Time management for CBSE students

The first thing to learn about Time Management is that time is theoretical so you can’t really manage it. What you do when you get into time management, is that you manage yourself. You decide what has to be done, when it must be done and how to do it in the stipulated...

Latest CBSE Syllabus for 2021 2022 PDF Download

Latest Syllabus for Class 12 for 2021 2022 Latest Syllabus for Class 11 for 2021 2022 Latest Syllabus for Class 10 for 2021 2022 Latest Syllabus for Class 9 for 2021 2022 CBSE has issued the latest syllabus for the academic year 2021 2022 which is applicable for all...

ICSE Board Exams Cancelled

The ICSE (Class X) 2021 Examination: Given the present worsening situation of the Covid- 19 Pandemic in the country, the CISCE has decided to CANCEL the ICSE (Class X) 2021 Examination. The options given in the earlier Circular dated 16th April 2021, now stands...

CBSE Assessment Framework

The Central Board of Secondary Education (CBSE) today, announced a suggested competency-based assessment framework to strengthen India’s existing school education system for secondary level (classes 6-10) and improve the overall learning outcomes of students across...

×
Studies Today