Informal vs. Formal Assessments. In order to properly understand what informal assessments are, we should first differentiate them from formal assessments. Formal assessments are designed to tell how well a student has progressed as evaluated against other students.
Rusting of iron consists of the formation of hydrated oxide, Fe(OH) 3, FeO(OH), or even Fe 2 O 3 .H 2 O. It is an electrochemical process which requires the presence of water, oxygen and an electrolyte. In the absence of any one of these rusting does not occur to any significant extent.
Other metals corrode. Rusting is an oxidation process. What we normally call rust is a flaky red-brown solid which is largely hydrated iron.The primary corrosion product of iron is Fe(OH)2 (or more likely FeO.nH 2 O), but the action of oxygen and water can yield other products having different colors:ther metals corrode. Rusting is an oxidation process. What we normally call rust is a flaky red-brown solid which is largely hydrated iron.The primary corrosion product of iron is Fe(OH)2 (or more likely FeO.nH 2 O), but the action of oxygen and water can yield other products having different colors: