Materials : Metals and Non Metals

Metals and Non Metals can be distinguished on the basis of their physical and chemical properties.

Physical properties of metals and non metals

The materials which generally possesses the following properties are metals:

Hard

Lustrous

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

Ductile: The property of metal by which it can be drawn into wires is called ductility.

Sonorous:The property in which metals produce ringing sound is called sonorous.

Good Conductors of  heat and electricity

Examples-Iron,copper,aluminium,calcium.magnesium.

The materials which generally possesses the following properties are Non Metals:

Soft and dull in appearance

Non Malleable

Non ductile

Non sonorous

Poor conductors of heat and electricity

Examples: sulphur ,carbon,phosphorous,oxygen etc

Chemical Properties of metals and non metals

Reaction with oxygen

Chemical Properties of Metals

1. Reaction of Metals with Oxygen: Generally, when metals are reacted with oxygen, they will form metallic oxides. These metallic oxides are basic in nature.

Example 1: Rusting of Iron. Following is the reaction to express it.

Iron (Fe) + Oxygen (O2) + Water (H2O) → Iron Oxide (Fe2O3)

Example 2:

2Cu + H2O + CO2 + O2→  Cu (OH)2 (copper hydroxide) + CuCO3 (copper carbonate)

2. Reaction of Metals with Water:  Some metals react vigorously with water like in case of sodium. It is stored in kerosene oil.

Some metals react with water to form metal oxides and metal hydroxides. Hydrogen gas is released in this reaction.

On the other hand, some metals react very slowly with water like in case of iron.

For example:

Na   + H2O        → NaOH    + H2

Sodium   + water →       Sodium hydroxide

M     + H2O      → Mg(OH)2  + H2

Ca      + H2O    → Ca(OH)2    + H2

Calcium  + Water    → Calcium hydroxide

Some metals react with cold water, some with hot water, and some metals react with steam. Metals which react with cold water are more stable as their hydroxides are stable.

For example: Potassium, Sodium, and Calcium.

K        + H2O        → KOH +       H2

Na     + H2O        → NaOH +      H2

Some metals react with hot water and form oxides. For example: Magnesium.

Mg                + H20   → MgO + H2

Magnesium             Water Magnesium oxide

Some metals react with steam.

For example: Aluminium, Iron, and Zinc.

Fe      + H2O      → Al2O3      + H2

Iron                (Steam)

Zn       + H2O      → ZnO       + H2

Al        + H2O      → Al2O3      + H2

Cu        + H2O     → No reaction

Tendency to react with water

The tendency of metals to react with water is as follows –

K> Na >  Ca > Mg > Al > Zn > Fe > Cu

More reactive >                               > not reactive.

3. Reaction of Metals with Dilute Acids:

Generally, a metal reacts with acids and releases hydrogen gas with a ‘pop’ sound.

For example:

Na     + HCl        → NaCl (Sodium chloride) + H2

Mg     + H2SO4   → MgSO4 ( Magnesium Sulphate)   + H2

Ca       + HNO3   → Ca(NO3)2 ( Calcium nitrate)  + H2

It is found that, copper does not react with hydrochloric acid while it reacts with sulphuric acid.

Cu (less reactive)  + HCL (more reactive)   → No reaction

Cu                            + HOH           → No reaction

Copper does not react with diluted acids and water. As copper is less reactive than HCl.

4. Reaction of metals with metals salt solution:

When salt of metal B reacts with metal A:

Salt of metal B       + Metal A →       Salt of metal A +  Metal

For example:

CuSO4(Blue color) +  Zn (more reactive) →       ZnSO4( colorless) + Cu

The five important uses of metals are as follows –

(i) Lead is used in X-ray machines.

(ii) Iron is used in construction.

(iii) Mercury is used in thermometers.

(iv) Gold and silver are used in making jewellery.

(v)  Aluminium foil is used for packing food.

Chemical Properties of Non-Metals

1. Reaction with oxygen: Oxides of non-metals are formed when non-metals react with oxygen. The oxides of non-metals are acidic in nature and turn blue litmus to red or neutral.

C       + O2   → CO2 (carbon dioxide, which is an acidic oxide)

When sulfur reacts with oxygen, we get sulfur dioxide.

S     +      O2      →       SO2

When sulfur dioxide reacts with water it forms sulphurous acid.

SO2    +      H2O      →     H2SO3

2. Reaction with water: Non-metals do not react with water but are usually very reactive in air, which is why some of them are stored in water.

For example, one of the highly reactive non-metals is phosphorus and it catches fire when exposed to air that is why it is stored in water to prevent its contact with atmospheric oxygen.

These non-metals do not have sufficient electrons to reduce hydrogen.

N.M    + HOH   → No reaction (non-metals do not displace or reduce hydrogen).

C         + H2O  → No reaction

3. Reaction with acids: None of the non-metals are known to react with acids.

C         + H2SO4  → No reaction

4. Reaction with bases: The reaction between non-metals and bases is a very complex one. Reaction of chlorine with bases like sodium hydroxide gives products like sodium hypochlorite as well as water.

The five important uses of non metals are:

(i) Sulphur is used in vulcanization of rubber, which makes rubber sufficiently hard to produce tyres.

(ii) Phosphorus is used in making phosphatic fertilizers.

(iii) Graphite is used in making lead of pencils.

(iv) Hydrogen can be used as a fuel that will be a non polluting option for fuel.

(v) Chlorine is added to water for purification purpose.

Corrosion

Corrosion is an oxidation reaction with atmospheric oxygen in the presence of water on the surface of a metal. During corrosion, metals get converted to oxides, hydroxides, sulphides, etc.

The corrosion of iron is called rusting.

The Conditions necessary for Rusting are as follows-

1. Moisture
2. Air

For example:

Fe  + O2  → Fe2O3 (Rust which is brown in color)   + H2O

Prevention of Corrosion (Rusting)

The steps involved in the prevention of corrosion are:

1. Painting: Coating a metal surface with paint or enamel provides a barrier between the metal and the moisture in the environment. For example: Railway coaches, automobiles, aircraft.

The process of coating a metal surface with another metal that is more likely to be oxidized is referred to as sacrificial coating.

2. Greasing: The application of greasing on metal surfaces is helpful in preventing the contact of the metal surface with air and moisture to prevent its corrosion. For example: Lubricating bicycle parts with grease to reduce friction and prevent corrosion.
3. Electroplating: It is the process of coating a thin layer of metal over the other alignment by hydrolysis. This process not only helps to prevent corrosion, but also makes the metallic surface shiny.

There are also specific types of electroplating such as copper plating, silver plating, and chromium plating.

4. Galvanization: It is the process of applying a protective thin layer of Zinc to steel or iron in order to prevent rust and corrosion.

EXERCISES

1 .a)zinc

2.c)Generally,metals are ductile

3.a)reactive

b)good,electricilty

c)more

d)hydrogen

4.a)false

b)true

c)false

d)false

5.

6. a) Aluminium foils are used to wrap food items because aluminium metal is malleable i.e. it can be beaten into thin sheets. It does not react with food items.
   b)Metals are good conductors of heat and electricity. Therefore , immersion rods for heating liquids are made up of metallic substances.
   c) In reactivity series a metal of higher reactivity can displace a metal of lower reactivity from its salt solution.Zinc is more reactive than copper therefore copper cannot displace zinc from its salt solution.
   Cu(s) + ZnSO4 (aq) ———–> No reaction
   d) Sodium and potassium are highly reactive metals. They can catch fire even when they come in contact with air. So, they have to be kept in kerosene.

8.

9, a)  Copper does not react with dilute sulphuric acid. So, no reaction takes place when dilute sulphuric acid is poured on a copper plate. But when concentrated sulphuric acid is poured over copper plate, effervescence is observed. This happens because of formation of hydrogen gas.
Cu + H₂SO₄ → CuSO₄ + H₂

b)When iron nails are placed in copper sulphate solution, the blue colour of copper solution is replaced by a light green colour. This happens because iron; being more reactive than copper; displaces copper from copper sulphate and makes iron sulphate.
CuSO₄ + Fe → FeSO₄ + Cu

10.a)  Saloni should bring a wet litmus paper (blue) near the evolved gas. When litmus paper turns to red it indicates that the evolved gas is acidic in nature.

1. b) Carbon (in charcoal) reacts with oxygen to produce carbon dioxide gas.
   C + O₂→ CO₂
   Carbon dioxide reacts with water to form carbonic acid.
   CO₂ + H₂O → H₂CO₃

11.Jewelers use Aqua Regia to clean jewelry. Gold is an inert metal which does not react with acids. But Aqua Regia is a mixture of hydrochloric acid and nitric acid in 3 : 1 ratio. It is so potent that it even dissolves gold and silver. Some of the gold is thus lost during cleaning of jewelry. This explains the weight loss of jewelry