Final answer:
1) A substance that is easily broken or shattered
The term 'brittle' describes a material that is easily broken or shattered, usually due to a crystalline structure that fractures along specific planes when force is applied.
Step-by-step explanation:
The term 'brittle' refers to a property of a substance indicating that it is easily broken or shattered. Brittle materials, such as some plastics and ionic compounds, tend to break rather than bend or deform when an external force is applied. Such materials usually have crystalline structures that cause them to fracture upon impact, breaking along specific planes. For instance, when a brittle ionic compound is struck by a hammer, it shatters due to the repulsion between similarly charged ions when layers are forced to shift.
Brittle materials differ from ductile materials, which can be drawn into wires, or malleable materials that can be easily shaped. Also, brittle materials should not be confused with thermal conductors that conduct heat or electrical conductors like copper wire that conduct electricity. In contrast to brittle materials, flexible materials can bend without breaking, and transparent substances allow light to pass through. The brittleness of a material is a crucial factor when determining its practical applications and how it handles stress and strain.