Solids have definite mass, volume and shape. Depending upon order, they are classified as crystalline solids and amorphous solids. Crystalline solids are further classified into molecular, ionic, metallic and covalent solids. Crystalline solids are made up of constituent particles which are arranged in a regular pattern, which is depicted in the form of three dimensional array of points in spaces called lattice points. Small characteristic repeating portion of lattice is called unit cell.
Unit cells can be primitive and also centred unit cells like face centred, body centred, end centred. Solids are not perfect. There are various types of defects (i) line defect (ii) point defect. Point defects are of three types : stoichiometric, impurity and non-stoichiometric defects. Solids show magnetic properties depending upon the orientation of electron.
Based on the paragraph Answer the following :
Certain properties of Crystalline solids are given below :
A. They have sharp melting points
B. They have long range order
C. They do not have definite enthalpy of fusion
D. They show anisotropy
E. Rubber, plastic are examples of crystalline solids
Incorrect statements are :
Choose the correct answer from the options given below :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → C and E only
(A) They have sharp melting points — A correct statement. A crystalline solid melts at a definite, characteristic temperature.
(B) They have long range order — A correct statement. The regular arrangement of particles repeats periodically throughout the crystal.
(C) They do not have definite enthalpy of fusion — An incorrect statement. Crystalline solids have a definite and characteristic heat of fusion; it is amorphous solids that do not.
(D) They show anisotropy — A correct statement. Physical properties such as electrical resistance or refractive index have different values in different directions.
(E) Rubber, plastic are examples of crystalline solids — An incorrect statement. Rubber and plastics are amorphous solids, like glass.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.