hardness
Definition
Hardness is a measure of the resistance of a material to localised plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example, hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behaviour of solid materials under force is complex; therefore, hardness can be measured in different ways, such as scratch hardness, indentation hardness, and rebound hardness.
How can the word be used?
The metal has a hardness of 5 on the Mohs scale.
Different forms of the word
Noun: hardness.
Adjective: hard.
Adverb: hardly.
Verb: harden.
Etymology
The word "hardness" comes from the Old English word "heard", which means "strong, firm, or difficult to break". The suffix "-ness" is used to form nouns that denote a quality or state.
Question
Why might it be useful to test the hardness of a material?
AQA Science Exam Question and Answer
Question:
Explain the concept of hardness in minerals and discuss the Mohs scale as a means of measuring mineral hardness.
Answer:
Hardness, in the context of minerals, refers to the resistance of a mineral's surface to scratching or abrasion. It is a fundamental property used to identify and classify minerals. The Mohs scale, developed by Friedrich Mohs in 1812, is a common method for measuring mineral hardness. The scale consists of ten minerals, each assigned a value from 1 (softest) to 10 (hardest). For example, talc has a hardness of 1, making it easily scratched, while diamond, the hardest mineral, has a hardness of 10.
To determine the hardness of a mineral, one simply attempts to scratch it with minerals of known hardness. If the mineral being tested can scratch a mineral with a lower number on the scale but is scratched by a mineral with a higher number, its relative hardness can be determined.
The Mohs scale is useful because it provides a quick and convenient way to compare the hardness of different minerals without specialised equipment. It aids geologists, mineralogists, and archaeologists in mineral identification and classification, which has implications for understanding the Earth's history, formation processes, and the properties of materials used by ancient civilizations.