Class -08, Chapter-04 METALS AND NON METALS Class-08(Science)

 

CHAPTER – 04

Class- 08 (Science)

Materials: Metal and Non metal

     Metal can be distinguished from non metal on the basis of their physical and chemical properties.

Physical properties of metal:-

1* Metals are lustrous, malleable, ductile and hard.

2* Metals are good conductor of heat and electricity.

3* They produce sonorous and have shiny appearance.

Ex. Iron nail/rod, aluminium, copper, calcium, magnesium etc.

 

Physical properties of non metal:-

1* Non metals have no lustrous, no malleable and no ductile property.

2*They have no sonorous.

3* They are poor conductor of heat and electricity.

4* They have dull appearance.

5* They breakdown into a powdery mass on tapping with a hammer.

Ex. Sulphur, Carbon, Oxygen, Phosphorus, Nitrogen etc.

 

MALLEABILITY:- The property of metals by which they can be beaten into thin sheets is called malleability.

 

LUSTRE:- The state or quantity of shining by reflecting light by metal.

 

SONOROUS:- Metals which are produce ringing sound; they are said to be sonorous.

 

DUCTILITY:- Able to be drawn out into a thin wire.

 

CONDUCTOR:- A conductor is any piece of material that easily allows heat or electricity to pass through it.

 

HARDNESS:- Metals are hard, on the other hand, non metals are generally brittle.

 

Appearance and hardness of material

Object/ Material	Appearance (shiny/ dull)	Hardness (very hard/ not hard)
Iron	Shiny	very hard
Coal	Dull	not hard
Sulphur	Dull	not hard
Aluminium	Shiny	very hard
Copper	Shiny	very hard

 

Malleability of material

Object / Material	Change in shape (Flattens / Break into piece)
Iron nail	Flattens
Coal piece	Break into piece
Aluminium wire	Flattens
Pencil lead	Break into piece

 

Electrical conductivity of materials

Material	Good / Poor conductor
Iron rod / nail	Good  conductor
Sulphur	Poor conductor
Coal piece	Poor conductor
Copper wire	Good conductor

 

** Metals like sodium and potassium are soft and can be cut with a knife.

** Mercury is the only metal which is found in liquid state at room temperature.

             These are exceptions.

 

Chemical properties of metals / non metals :-

(1)- Reaction with oxygen:- Rusting of iron and burning a magnesium ribbon in air, in both the process oxide formation take place.

** Iron(Fe)+Oxygen(O₂)+ water(H₂O)

                    → Iron oxide (Fe₂O₃)

 

**Magnesium(Mg)+Oxygen(O₂)   

            → Magnesium oxide (2MgO)

 

 > Oxides of metals are basic in nature

           In the reaction between sulphur and oxygen, sulphur dioxide gas is formed.

**Sulphur(S)+Oxygen(O₂)  → Sulphur dioxide (SO₂)

   

     When sulphur dioxide is dissolved in water sulphurous acid is formed.

**Sulphur dioxide (SO₂)+ water(H₂O)

         →  sulphurous acid (H₂SO₃)

 

> Oxides of non metals are acidic in nature.

 

(b)- Reaction with water:- Sodium metal reacts vigorously with water, some other metals do not react. Like iron reacts with water slowly.

 

> Generally non metals do not react with water. They may be very reactive in air, such non metals are stored in water. Ex Phosphorus

 

(3)- Reactions with Acids:- Non-metals generally do not react with acids but metals react with acids and produce hydrogen gas that burn with a ‘POP’ sound.

 

> Copper does not react with dilute hydrochloric acid even on heating but it reacts with sulphuric acid.

 

(4)- Reaction with bases:- Metals react with sodium hydroxide to produce hydrogen gas.

 

> Reaction of non metal with bases are complex.

 

(5)- Displacement reactions:- A more reactive metal can replace a less reactive metal, but a less reactive metal can not replace a more reactive product.

Ex.

>  CuSO₄ + Zn       →      ZnSO₄  +  Cu

>  CuSO₄ + Fe        →     FeSO₄  +  Cu

      Zn and Fe are more reactive than copper sulphate. so they replace Cu from CuSO₄ .

 

>  ZnSO₄ + Cu    →         No change

>  FeSO₄ + Cu        →     No change

      Cu is less reactive than ZnSO₄ and FeSO₄. So they can not replace Fe from Zn.

 

Uses of metals and non metals:- Metals are used in making machinery, automobiles, aeroplanes, trains, satellites, industrial gadgets, cooking utensils, water boiler etc.

 

** Non metals is essential for our life which all living being inhale during breathing. (O₂)

** Non metals are used in fertilizers to enhance the growth of plants.(N₂)

** Non metals are used on wound as an antiseptic.

** Non metals are used in making crackers.

 

Metals and non metals in acid and bases.

SN	Name of base	Metal	Name of acid	Non metal
1	Calcium hydroxide	Calcium	Sulphuric acid	Sulphur
2	Sodium hydroxide	Sodium	Nitric acid	Nitrogen
3	Magnesium hydroxide	Magnesium	Hydrochloric acid	Hydrogen
4	Potassium hydroxide	Potassium	Carbonic acid	Carbon

 

Atom:- Atom is the smallest particle of matter which cannot be divided further by any physical means. Atoms are the basic units from which molecules and ions are formed.

 

Elements:- Substances whose molecules contain only one type of atoms are known as elements.