Chapter 4 - Materials : Metals and Non-Metals

Metals can be distinguished from non-metals based on their physical and chemical properties.

PHYSICAL PROPERTIES OF METALS AND NON-METALS

• The property of metals by which it can be beaten into the thin sheets is called malleability. This is the characteristic properties of metals.
• The property of metals by which it can be drawn into wires is called ductility.
• Metals produce ringing sound while striking by other material, they are said to be sonorous.
• Examples of metals are iron, copper, calcium, aluminium etc.

• Non –metals do not possess such characteristic like metals.
• Materials like coal and sulphur are soft and dull.
• They are non-sonorous and poor conductor of heat and electricity.
• Example of non-metals are- sulphur, carbon, oxygen etc.

CHEMICAL PROPERTIES OF METALS AND NON-METALS

REACTION WITH OXYGEN

For metals

Metals react with oxygen to form metallic oxides. Metals are basic in nature.

Example 1

When iron reacts with air, it forms rust that is iron oxide.

Iron (Fe) + oxygen (O₂) + water (H₂O)

Iron Oxide (Fe₂O₃)

Example 2

If a copper vessel is left open in presence of the moist air, then a green coating occurs.

2Cu + H₂O + CO₂ + O₂

Cu (OH) ₃ + CuCO₃

For non-metals

Non-metals also produce oxides when reacted with oxygen. These oxides are acidic in nature.

Example 1

When sulphur reacts with oxygen it will form sulphur dioxide. Further when sulphur dioxide dissolve in water sulphurous acid is formed. This sulphurous acid turns blue litmus paper red.

S + O₂

SO₂

REACTION WITH WATER

Generally, metals form respective hydroxides when they react with water. Such as sodium metals vigorously reacts with water and forms sodium hydroxide along with lot of heat.

Example-1

Na + H₂O

NaOH + H ₂ + Heat

Similarly, potassium metal vigorously reacts with water and forms potassium hydroxide along with lot of heat.

Non-metals generally don’t react with water. Rather some of the non-metals which react with air vigorously are stored in water to avoid reaction.

REACTIONS WITH ACIDS

Metals give hydrogen gas every time when they react with dilute acid.

Example 1

Zn + HCl

ZnCl₂ + H₂

Zinc gives hydrogen gas along with zinc chloride when they react with hydrochloric acid.

Similarly zinc also gives hydrogen gas when it reacts with sulphuric acid.

Whereas, non-metals don’t react with acids. Also, metals like copper does not react with dilute sulphuric acid even on heating, but it reacts with concentrated sulphuric acid.

REACTIONS WITH BASE

Metals give hydrogen gas when they react with the base. It produces pop sound when the match stick is put above the mouth of the beaker.

Example-1

Aluminium metal with sodium hydroxide forms hydrogen gas and sodium aluminates.

Al + NaOH+ H₂O

NaAlO₂ + H₂

Reactions of base with non-metals are complex.

DISPLACEMENT REACTION

When a more reactive metal reacts with the salt solution of less reactive metal, more reactive metal displaces the less reactive metal from its solution

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Metal A + Salt Solution of Metal B

Salt Solution of Metal A + Metal B

In above equation, metal A is more reactive than metal B, so B will be displaced.

Example 1

When aluminium metal is dipped in the solution of copper sulphate, it forms aluminium sulphate and copper.

Al +CuSO₄

Al ₂(SO₄)₃ + Cu

Example 2

When iron reacts with solution of copper sulphate, it gives iron sulphate and copper

Fe + CuSO₄

FeSO₄ + Cu

In the above two reactions, aluminium and iron are more reactive than copper, that’s why they replace copper from the solution of copper sulphate.

USES OF METALS AND NON-METALS

Use of metals

• Metals are used in making machinery, buildings, car, motorcycle, ships, bridge, etc.
• Copper is used in making electric wires, statue, etc.
• Gold and silver metal is used in making ornaments.

Use of Non-metals

• The number of non-metals is very less in comparison to metals, but non-metals are more useful for us. So far only 22 non-metals are discovered.
• Non-metal essential for our life which all living being inhales during breathing.
• Sodium chloride (common salt) cannot be formed without chlorine (a non-metal) which we use to enhance the taste of food. Without using common salt, food is tasteless.
• Non-metals used in fertilizers to enhance the growth of plants.
• Used in purification process.