sentences: a nail often is made of wood & when a wood standard , that wood becomes flaky on the bottom ->  when a hammer rusts, the hammer will becom flaky on the surface  when a hammer rusts, the hammer will becom flaky on the surface & kim's nail is flaky on the bottom ->  the hammer has rusted  the hammer has rusted & quality forming is a mean of physical static -> the hammer has undergone a chemical change