Difference between Crystalline and Amorphous Solids

Introduction

• States of Matter: Solids, liquids, and gases.
• Solid Characteristics: Definite shape.
• Categories of Solids: Crystalline and amorphous (glassy) solids.

Differences between Crystalline and Amorphous Solids

Atomic Arrangement

• Crystalline Solids: Atoms are arranged regularly.
• Amorphous Solids: Atoms are not arranged regularly.

Order of Atoms

• Crystalline Solids: Long-range order (atoms are arranged from far to near).
• Amorphous Solids: Short-range order.

Melting Point

• Crystalline Solids: Sharp melting point.
• Amorphous Solids: No sharp melting point, melts over a range of temperatures.

Anisotropy vs. Isotropy

• Crystalline Solids (Anisotropic): Physical properties (mechanical, electrical, optical) differ in different directions.
• Amorphous Solids (Isotropic): Physical properties are the same in all directions.

True Solids

• Crystalline Solids: Considered true solids.
• Amorphous Solids: Not considered true solids.

Examples

• Crystalline Solids: Mica, diamond, sodium chloride (NaCl).
• Amorphous Solids: Glass, rubber, plastic.

Conclusion

• Summary of Differences: Arrangement of atoms, order of atoms, melting point, anisotropy/isotropy, categorization as true solids, and examples.
• Assessment: These differences can be asked as compulsory questions worth two marks or as part of a longer question in exams.

Next Steps

• Upcoming Lecture: Further differences between crystalline and amorphous solids.