Metallurgy, properties of metals

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Source: Internet

Earth was born about 4.5 billion years ago. Various formative processes have been taking in the core of the earth and it's surroundings  since its creation today. These have resulted in the formation of various ores, liquids and gases. 

Physical properties of metals:

Metal exist mainly in solid state. The metals namely, Mercury and gallium exist in liquid state at room temperature. Metals posses luster. The metallic luster goes on decreasing due to exposure to atmospheric oxygen and moisture and also in presence of some reactive gases.
We know that metals have the properties namely, ductility and malleability. Similarly, all metals are good conductors of heat and electricity. Generally, all metals are hard. However, the alkali metal from group 1 such as lithium, sodium and potassium are exceptions. These metals can be cut with knife as they are very soft. Metals have high melting and boiling points. For example, tungsten metal has the highest melting point (3422°C). On the contrary, the melting and boiling points of the metals such as sodium, potassium, Mercury, gallium are very low. A sound is produced when certain metals are struck. This is called sonority. These metals are known as sonorous metals.

Physical properties of nonmetals:

When properties of nonmetals are considered, it is found that some nonmetals are in solid state while some are in a gaseous state. Exception is the nonmetal bromine which exist in liquid state. Nonmetals do not possess lustre, but iodine is the exception its crystal are shiny. Nonmetals are not hard. Diamond which as an allotrope of carbon is the exception. Diamond is the hardest natural substance. Nonmetals have low melting and boiling points. Nonmetals are bad conductors of electricity and heat.Graphite, an allotrope of carbon, is an exception, as it is good conductor of electricity.

Chemical properties of metals:

Metals are reactive.They lost electrons easily and become positively charged ions. That is why metal are called electropositive elements.

Reaction of Metals:

a) Reaction of metals with oxygen

Metals combine with oxygen on heating in air and metal oxides are formed. Sodium and potassium are very reactive metals. Sodium metal combines with oxygen in the air even at room temperature and forms sodium oxides.

                        4Na(s) + O2(g) → 2Na2O(s) 

On  exposure to air sodium readily catches fire. Therefore, to prevent accident in the laboratory or elsewhere it is kept in kerosene. Oxides of some metals are soluble in water. They react with water to form alkali.
 
                       Na2O(s) + H2O(l) →  2NaOH (aq)
 
We know that magnesium oxides is formed on burning magnesium ribbon in the air. Magnesium oxide react with water to form alkali, called magnesium hydroxide.
 
                       2Mg(s) + O2(g) → 2MgO(s)
 
                        MgO + H2O  → Mg(OH)2

Reactions of metals with water:

Apparatus: Beaker 
Chemicals: Samples of various metals (Important note: Sodium metal should not be taken), water. 
Procedure:Drop a piece of each of the metal in the separate beakers filled with cold water. 
 Sodium and potassium metal react rapidly and vigorously with water and liberates hydrogen gas.

          2Na(s) + 2H2O(l) → 2NaOH (aq) + H2(g)+ heat
           2K(s) + 2H2O(l) ⟶ 2KOH (aq) + H2(g)+heat

On the other hand, calcium reacts with water slowly and less vigorously. The hydrogen gas released in this reaction collects on the surface of the metal in the form of the bubbles and the metal float on water.
             
             2Ca(s) + H2O (l) ⟶ 2Ca(OH)2(aq) + H2(g)

The metals; aluminium, iron and zinc do not react with cold or hot water, but they react with steam to form their oxides. Hydrogen gas is released in this reaction.

             2Al(s) + 3H2O(g) ⟶ Al2O3 (s) + 3H2 (g)
             3Fe(s) + 4H2O(g) ⟶ Fe3O4(s) + 4H2O (g)
             Zn(s) + H2O (g) ⟶ ZnO(s) + H2(g)

Reaction of metals with oxygen:

When samples of aluminium, magnesium, iron ore of zinc are treated with dilute sulphuric or hydrochloric acid, sulphate or chloride salts of metals are formed. Hydrogen gas is liberated in this reaction. The reactivity of these metals can be indicated by the following sequence
         Mg >Al > Zn> Fe

       Mg(s) + 2HCl(aq) ⟶ MgCl2(aq) + H2(g)
       2Al (s) + 6HCl (aq) ⟶ 2AlCl3(aq) + 3H2(g)
       Fe(s) + 2HCl( aq) ⟶ FeCl2(aq) + H2(g)
       Zn(s) + HCl(aq)  ⟶ ZnCl2(aq) + H2(g)

Reaction of metals with nitric acid:

Nitrate salts of metals are formed on reaction of metals with nitric acid. Various oxides of nitrogen (N2O, NO, NO2) are also formed in accordance with the concentration of nitric acid.

Cu(s) + 4HNO3(aq) ⟶ Cu( NO3)2(aq) + 2NO2(g) + 
             ( Conc.)
H2O


3Cu(s)+8HNO3(aq) ⟶ Cu(NO3)2 (aq)+2Na(g)+4H2O
                (Dil.)





 

 
 
 
 
 
 

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