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SAI International School
Class-X

Subject_ Chemistry
Topic-Chemical Reactions and Equations
Sub topic-Corrosion & Rancidity

LESSON NOTES

Examples of OXIDATION-

CORROSIONRANCIDITY
The wearing out of metals layer by layer, The oxidation of fats and Oil
due to their reaction with atmospheric present in food itemsto give
gases,in presence of moisture,is knownout afoul smell and bitter
as Corrosion. taste is known as Rancidity.

 CORROSION-
Corrosion may be of two types:

This phenomenon protects the This phenomenon destroys the
metal from further corrosion metal gradually or makes the
Example- Corrosion of Al, Mg, Zn surface dull & lustre less.
Example- a. Rusting of Fe,
b. Tarnishing of Ag,

c. Corrosion of Cu.

1. Positive Corrosion-
Metals like Al, Mg, & Zn being reactive in nature, react readily with
atmospheric gases like Oxygen & Carbon-dioxidein presence of moisture,
to form a sticky layer of the corresponding metal oxide/carbonate, which
acts as a protective coat & prevents the metal from further exposure to
air & moisture (Corrosion).

Application- a. Galvanizing of iron using Zn.
b.Al is used to make door & window frames, Chairs, Utensils,
c. Mg is used in the form of its alloy to make parts of space crafts, vehicles
etc.

2. Negative Corrosion-
a. Corrosion of Iron-

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