How would you describe the relationship between crystalline order and rigidity?

• A. Greater crystalline order -> greater rigidity.
• B. Greater crystalline order -> lower rigidity.
• C. Higher crystallinity raises rigidity because crystalline regions are more rigid than amorphous.
• D. They are unrelated.

Answer: (C)

Rigidity in a solid comes from how freely atoms or molecules can move under stress. When there is higher crystalline order, the material contains regular, long-range packed regions that constrain movement and provide a stiff framework. Crystalline regions have higher bond density and less conformational freedom, so they transmit and resist stress more effectively than amorphous areas. As a result, increasing crystallinity generally raises rigidity.

Of course, the exact effect depends on how much of the material is crystalline, how well those crystals are connected, and the temperature relative to the material’s transition points. If crystals are small or poorly connected, or if you’re near where the material softens, the boost in rigidity may be limited. But the overarching idea is that crystalline regions are inherently more rigid than amorphous ones, so more crystallinity tends to make the material stiffer.