Corrosion

Question 1 Define the term corrosion?

Question 2 What is meant by rusting of iron?

Question 3 State the conditions necessary for rusting of iron?

Question 4 State the ways to prevent the rusting of iron?

Question 5 Name the metal used for galvanising iron?

Question 6 Why copper objects lose their shine after sometime?

Question 7 Why silver articles became black when exposed to air?

Question 8 Why gold ornaments look new even after several years of use?

Corrosion

The eating up of metals by the action of air,moisture or a chemical on their surface is called corrosion.

The copper objects lose their shine after sometime due to the formation of copper oxide on them.When a copper object reacts with moist carbon dioxide,it loses its shiny brown surface and gains a green coat(basic copper oxide which is a mixture of copper carbonate and copper hydroxide)

Silver articles became black after sometime when exposed to air because it react with sulphur in air to form a coating of silver sulphide.

The corrosion of iron is called rusting.When an iron object is left in damp air for a considerable time,it gets covered with a red brown flaky substance called rust.
Rust is hydrated iron(III) oxide.The formula of rust is Fe2O3.nH2O
The two conditions necessary for rusting of iron is presence of air and water.

Prevention of rusting

1)By painting
2)BY applying grease or oil.
3)By galvanisation:The process of depositing a thin layer of zinc metal on iron.
4)By tin plating and chromium plating.
5)By alloying it

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