How is hardness defined in materials?

Hardness is a characteristic that describes how resistant a material is to deformation, particularly when it comes to penetration or scratching. This definition highlights the material's ability to withstand surface wear and abrasion, making hardness a crucial property in many applications.

When assessing hardness, various methods can be applied, including scratch tests, indentation tests, and rebound tests, all of which seek to quantify how much force or pressure a material can endure before it is marked or penetrated. For example, a harder material will leave less of an impression when a sharp object is pushed against it compared to a softer one. This characteristic is vital for selecting materials in engineering and design, as it influences durability, wear resistance, and overall functionality in different environments.

The other options, while important material properties, do not define hardness. The ability to withstand being pushed or squashed relates more closely to a material's strength or toughness rather than its hardness. The ability to conduct electricity pertains to a material's electrical conductivity, while the ability to be drawn into wires refers to ductility, which describes how readily a material can deform under tensile stress. Each of these properties serves distinct purposes and applications in material science.