Chapter 3: Physical and Chemical Changes

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Physical and Chemical Changes


Explain how painting of an iron gate prevents it from rusting.


Rusting is the process of the formation of a brown layer on iron substances when exposed to moist air (which contains oxygen and water). This brown layer on the surface of iron is hydrated iron oxide or rust. It is a chemical and irreversible change.

The two essential conditions for rusting of iron objects are water (moisture) and oxygen. The rusting of iron can be prevented by applying paint or grease on the surface of the iron objects. The paint or grease acts as a barrier and cuts off the contact of metal surface with air and moisture, thus preventing rusting of the iron objects.



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