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Metals - Lesson Summary

Metals are strong and durable. Thus metals are used so widely for making almost everything. 
Example: Metals are used in making machinery, automobiles, aeroplanes, buildings, trains, satellites, gadgets, cooking utensils, water boilers...etc.

However not all metals are hard, strong and durable solids. Sodium and potassium are soft metals which can be cut with a knife. Mercury is a liquid metal.

Physical Properties of Metals
The metal base in an electric iron is for conducting heat, not electricity.
Metals are very good conductors of heat. Cooking utensils, irons, heaters, etc. are all made of metals which are good conductors of heat.

Metals can be easily shaped into wires. This property of metals is called ductility.
Metals can be easily shaped into thin flat sheets. This characteristic of metals is called malleability.
Metals make a sound when struck with hard objects. Metals can be polished to a shiny appearance. 

Chemical Properties of Metals
Rust formation

Iron reacts with atmospheric oxygen and moisture to form iron oxide, which is commonly known as rust. Nails rust because of the moisture present in air. 
Iron when reacted with both water and oxygen which present in air (moist air), corrodes. Its silvery colour changes to a reddish-brown, because hydrated oxides are formed which is commonly called as rust.
Reaction showing formation of rust when reacted with water in presence of oxygen (atmosphere).     
4Fe + 3O₂+ XH₂O → 2Fe₂O₃.XH₂O       

Similarly when a copper vessel is exposed to moist air, a green coating forms on its surface. The coating is a mixture of copper hydroxide and copper carbonate.

Reaction with oxygen
Metals burn in the presence of oxygen to form metal oxides. These metal oxides are basic in nature.
Burning a strip of Magnesium: Magnesium will burn in oxygen to form magnesium oxide.
                              2Mg + O2 → 2MgO
Magnesium oxide dissolves in water to form magnesium hydroxide, which is basic in nature.
                            MgO + H2O → Mg(OH)2

Reaction with water
Not all metals reacts with water. Highly reactive metals can react with water.
Example: Sodium reacts vigorously with water and oxygen and produces large amount of heat. Because of its high reactivity sodium is stored in kerosene - to prevent it from coming into contact with moisture and oxygen.

Reaction with acids
Metals react with acids and produces hydrogen gas.
                                    Zn + 2HCl → ZnCl2 + H2
                                  Na + H2SO4 → Na2SO4 + H2
Copper does not react with dilute hydrochloric acid even on heating, but it reacts with dilute sulphuric acid on heating.
                          Cu + dil.H2SO4 (heating)  → CuSO4 + H2

Reaction with bases
Only few metals can react with strong bases to metal salts and releases hydrogen gas.
Example: Zinc metal reacts with sodium hydroxide to form sodium zincate and hydrogen gas.
                                     Zn + NaOH → NaZnO2 + H2


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