Materials: Metals and Non-metals Class 8th notes ( NCERT )

All the materials in the world can be classified into either metal or non-metal.

The materials are classified into either of them on the basis of the material's physical and chemical properties. Let us find out those properties.

Metals

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Physical Properties of Metals

The physical properties of metals are-

1. Hard

It is difficult to mold metals into another shape. Sodium (Na) and Potassium (K) are exceptions of this property.

2. Solid

All the Metals are solid at room temperature with the exception of Mercury (hg) which is liquid at room temperature.

3. Ductile

Metals can be drawn into wires. For example, Aluminium and copper are drawn into wires and used in daily life.

3. Lustrous

Metals have a natural shine. For example, Gold and silver have a natural shine in them. Because of their natural shine they are also used in jwellery.

4. Sonorous

Metals produce sound. For example, If you tap an iron rod it would probably produce a sound.

5. High Melting point

Metals have a high melting and boiling point with the exception of Gallium (Ga) and Cesium (Cs).

6. Malleable 

Metals can be beaten into thin sheets. For example, Aluminium is beaten into thin sheet/Aluminium foil and is generally used to wrap food.

7. Good conductor of electricity and heat

Metals are good conductors of electricity and heat with the exception of lead and Mercury (hg).

Chemical properties of metals

1. Metal+Oxygen= Metal Oxides (Basic)

i.e.  2Mg(Magnesium) + O²(Oxygen)= 2MgO(Magnesium oxide)

2.Metal+ Water = Bases

i.e.   Na(Sodium) + H²O = NaOH(Sodium Hydroxide)

3.Metal+ Acid = Salts + Hydrogen

i.e.  Mg (magnesium) + 2HCI (hydrochloric acid)= MaCI (Magnesium Chloride) + H²(Hydrogen)

 Non-metals

Physical properties of Non-metals

1. Brittle

Non-metals are not as hard and strong as metals and are fragile in comparison to metals. For example, plastic items would not be as strong as an item made out of iron.

2.Can exist as Solid, Liquid or Gas at room temperature

Non-metals can exist in any state in room temperature.  For example, Bromine exists in liquid state while plastic exist in solid state. 

3. Non- Ductile

Non-metals cannot be drawn into wires. When beaten, non-metals can easily break . Thus, they cannot be drawn into wires.

4. Non- lustrous

Non metals do not have a natural shine in them with the exception of iodine(I) which is a non-metal but has a shine in it.

5. Non-sonorous

Non-metals do not produce sound as metals. For example, bells are not made out of non-metals because they are not capable of making sounds as loud as metals.

6. Non-malleable

Metals cannot be beaten sheets because as it is mentioned above, non-metals can easily break while beaten.

7. Poor conductors of heat and electricity

Non-metals are poor conductors of heat and electricity. For example, wood and plastic are poor conductors of electricity.