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.
When a metal undergos a combination reaction with oxygen, a metal oxide is formed (similarily, a metal halide is formed if reacted with one of the halogens). You see the products of this type of reaction whenever you see rust. Rust is the product of a combination reaction of iron and oxygen:hen a metal undergos a combination reaction with oxygen, a metal oxide is formed (similarily, a metal halide is formed if reacted with one of the halogens). You see the products of this type of reaction whenever you see rust. Rust is the product of a combination reaction of iron and oxygen: