Understanding Material Properties: Brittleness Explained

The question asks about the material property that describes the tendency of a material to break or fracture with very little or no noticeable permanent deformation before breaking. Let's look at the given options and see which one fits this description.

• Plasticity: This is the ability of a material to undergo permanent deformation under stress without fracturing. Materials that can be easily shaped or molded exhibit high plasticity. This is the opposite of fracturing without appreciable deformation.
• Stiffness: This property refers to a material's resistance to elastic deformation under load. A stiff material requires a large force to deform it slightly. Stiffness is related to the material's Young's modulus. It doesn't directly describe the tendency to fracture with little deformation.
• Brittleness: This is the tendency of a material to fracture with very little or no plastic deformation. Brittle materials absorb relatively little energy prior to fracture. Examples include glass, ceramics, and cast iron. When a brittle material fails, it typically does so suddenly and without significant warning (like stretching or bending). This definition perfectly matches the description in the question.
• Toughness: This is the ability of a material to absorb energy and plastically deform before fracturing. A tough material can withstand impact and deform considerably before breaking. This is the opposite of brittleness, which involves fracturing with little deformation and energy absorption.

Based on the definitions, the tendency of a material to fracture without appreciable deformation is precisely what is meant by brittleness.