sentences: an example of breaking something down is scratching something & a material that is soft can be broken down by a material that is hard ->  a material that is soft can be scratched by a material that is hard  a material that is soft can be scratched by a material that is hard & a mineral is a kind of material ->  if one mineral can scratch another mineral then that other mineral is softer than that one mineral  if one mineral can scratch another mineral then that other mineral is softer than that one mineral & hardness is a measure of a mineral 's ability to resist scratching -> measuring the hardness of minerals requires scratching those materials