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Reactivity Series and Uses of Metals, Non-metals and Alloys- Chemistry Guide for Class 8

Information about Reactivity Series and Uses of Metals, Non-metals and Alloys

Title

Reactivity Series and Uses of Metals, Non-metals and Alloys

Class

Class 8

Subject

Class 8 Chemistry

Topics Covered

  • Reactivity of Metals
  • Reactivity Series
  • Displacement Reactions
  • Noble Metals
  • Uses of Common Metals
  • Uses of Alloys
  • Uses of Non-Metals


Reactivity of Metals

  • The tendency of an element to react with other substances to form compounds is an indicator of its reactivity. The more is the tendency of an element to form compounds, the more is its reactivity. 
  • All metals do not have the same reactivity. Some are more reactive than the others, that is, they have a greater tendency to form compounds. Such metals occur in the form of their compounds in earth's crust.
  • Lesser reactive metals occur in their native state, that is, elemental state.
  • On the basis of experiments, involving the reaction of different metals with a particular substance, metals have been arranged in the decreasing order of their reactivity.
  • The series of metals, arranged in the order of their decreasing reactivity, is called the reactivity series

The reactivity series of Metals Table

Symbol of the element

Name of the element

K

Potassium

Na

Sodium

Ca

Calcium

Mg

Magnesium

Al

Aluminium

Zn

Zinc

Fe

Iron

Sn

Tin

Pb

Lead

Cu

Copper

Hg

Mercury

Ag

Silver

Au

Gold

Pt

Platinum

Potassium is the most reactive metal while platinum is the least reactive. 

Displacement Reactions

Reaction of a metal, with an acid, is an example of a displacement reaction in which the metal displaces hydrogen from the acid.
A reaction, in which a more reactive metal displaces a lesser reactive metal from the aqueous solution of its salt, is another example of a displacement reaction.

Activity 1

Take 50 ml of water in a beaker and dissolve a few crystals of copper sulphate in it. A blue coloured solution is obtained. Dip a magnesium ribbon in this solution. You will observe that the blue colour of the solution fades and after sometime, the solution becomes colourless. Also, the magnesium ribbon gets coated with a brown layer. 
  • This happens because magnesium, being more reactive than copper, displaces it from copper sulphate.
  • The magnesium sulphate formed is colourless and the copper metal, that gets deposited on the magnesium ribbon, appears as a brown coating.
  • This displacement reaction can be represented by the following equation:

Noble Metals

  • As seen from the reactivity series, platinum is the least reactive metal. It does not react with air, water, acids, bases and most other substances. Another metal, which shows a similar behaviour, is gold. Gold and platinum are called noble metals.
  • Since noble metals are least reactive, they are not chemically affected by the substances around them. Hence, they do not get tarnished, and retain their lustre for a very long time. 
  • Both, these noble metals are also highly ductile and malleable; they can be drawn into extremely thin wires and can be beaten into very thin foils. It is because of these properties that gold and platinum are used for making jewellery.
  • Gold can also be used for plating other metals, like copper and silver. Platinum is used in dentistry and in making scientific instruments. 
  • Pure gold is very soft. Therefore, it cannot be used for making jewellery in its pure form. Hence, for making jewellery, it is often mixed with silver or copper to make it appropriately hard. 
  • The purity of gold is expressed in terms of carats (or karats). The carat number gives the number of parts of gold present in 24 parts of a mixture of gold with the other metals.
    For example, 22 carat gold means that 22 parts of pure gold is present in 24 parts of a mixture of gold with copper (or silver). This implies that pure gold would be rated as: '24 carat gold'. 

Uses of Metals, Alloys and Non-Metals 

Uses of Common Metals

Metals have been an integral part of our daily life since ancient times. They have played an important part in the development of different civilisations.
Even today, metals are used for a variety of purposes in our day-to-day life. The most commonly used metals, in every day life, are iron, copper, aluminium and silver.
  • Iron is the most widely used metal. It is used for making cooking vessels, water boilers, stoves, toys, tools, pipes, agricultural implements, chains, wires, nails, bolts, electromagnets, and so on.
  • Aluminium, being a very light metal, is used for making aircraft bodies. It is also used for making cooking vessels. Its thin foils are used for packaging of food stuffs and medicines.
  • Copper is the most widely used metal for making electrical cables and other electrical goods. It is also used for making cooking vessels.
  • Silver is used for making jewellery, decoration pieces, tableware, etc. Silver, being highly malleable, can be converted into very thin foils which are used for decorating food items. Silver is a very good conductor of electricity, but it is not commonly used for electrical fittings because it is very expensive. Silver and Gold wires are, however, used for high precision electrical contacts in computers. 

Uses of Alloys

Besides being used in their pure form, metals are also often used in the form of their alloys. An alloy is a homogenous mixture of two or more metals, or a metal and a non-metal.
  • By adding appropriate amount of other metals, or non-metals, to form the alloys, the properties of a given metal can be (significantly) modified.
  • Alloys are generally stronger, harder and more resistant to corrosion than the (pure) metal itself.
Uses of some common alloys

Name of the Alloy

Made From

Used for making

Steel

iron + carbon

construction material, machine parts

Stainless steel

iron + chromium + nickel

cooking utensils and cutlery, surgical implements

Brass

copper + zinc

cooking utensils, decorative statues, nuts and bolts

Bronze

copper + tin

cooking utensils, coins, medals, statues, decorative items

German Silver

copper + zinc + nickel

tableware

Duralumin

aluminium + copper + magnesium + manganese

aircraft bodies, automobile parts, undersea vessels

Alnico

aluminium + nickel + cobalt

magnets

Gun metal

copper + tin + zinc

gun-barrels


Uses of Non-Metals

Some of the common uses, of some of the well-known non-metals, are given below:
  1. Nitrogen, in the form of fertilisers, is essential for the growth and development of seeds and plants.
  2. Phosphorus is used in matchbox industry and in fertilisers.
  3. Iodine is used as an antiseptic.
  4. Sulphur is used for making fire crackers, gun powder and sulphuric acid.
  5. Oxygen is essential for survival of all living beings.
  6. Diamond (a form of carbon) is used in making jewellery, in cutting glass and for grinding of tools.
  7. Graphite (also a form of carbon) is used in batteries and in pencils.

Some Important Points

Many metals, and some non-metals, play a vital role in the functioning of the human body.
  • Iron is an essential and important component of haemoglobin; its deficiency can lead to serious complications.
  • Sodium and potassium play an important role in the transmission of (electric) signals, to and from, the brain.
  • Several other metals also play an important role in the human body.
  • Non-metals, like carbon and phosphorus, also play an important role in human body.
  • Phosphorus is present in bones and helps cells obtain energy from food. 
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