To observe the action of Zn, Fe, Cu and Al metals on the following salt solutions:
- ZnSO4 (aq)
- FeSO4 (aq)
- CuSO4 (aq)
- Al2(SO4)3 (aq)
Arrange Zn, Fe, Cu and Al metals in the decreasing order of reactivity based on the above results.
Metals are elements and are good conductors of heat and electricity. Most metals are electropositive in nature and the metal atoms lose electrons in chemical reactions to form cations. The more reactive a metal, the greater tendency it has to form a positive ion in a chemical reaction.
How are metals arranged in a periodic table?
Metals occupy the bulk of the periodic table. The alkali metals are a series of chemical elements in the periodic table. Alkali metals comprise group 1 in the periodic table along with hydrogen. Alkali metals are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs) and francium (Fr). The group 2 elements in the periodic table are called alkaline earth metals. Alkaline earth metals are beryllium (Be), magnesium (Mg) calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Group1 and group 2 elements are together called s-block elements. Elements of group 3 to 12 are transition elements. These are also metallic in nature and are called transition metals. They are also called d-block elements. Non-metallic elements occupy the right side of the periodic table. A diagonal line from boron to polonium separates metals from non-metals.
Now, let’s explore the properties of metals…
Physical properties of metals:
- Good conductors of heat and electricity: In metals, the positive ions are surrounded by a sea of electrons and these are responsible for their conductivity.
- High melting point and boiling point.
- They are malleable and ductile, so they can be bent and stretched without breaking.
- In most metals, the atoms are highly close packed, so they have high density.
- They have a shiny appearance.
- Metals exist in solid state at room temperature except for mercury, which is in a liquid state at room temperature.
Chemical properties of metals:
- A more reactive metal readily reacts with other elements. The most reactive metals will react even water, while the least reactive metals will not react even with acid.
Example: If we put a small piece of sodium metal in water, sodium reacts exothermically with water producing hydrogen and metal hydroxide.
Metals react with oxygen in the air to form oxides.
- Some metals react with acid and replace hydrogen from the acid.
- Single displacement reactions:
A single displacement reaction is an important type of chemical reaction. It is also called substitution reaction. In these reactions, a free element displaces another element from its compound, producing a new compound. The reaction is usually written as:
Single displacement reactions are all oxidation-reduction reactions. For example,
Definition of Displacement reaction: The chemical reaction by which one element takes the position or place of another element in a compound.
Displacement reactions are very common in metals. They can be used to find out the relative reactivities of metals. In a displacement reaction, a more reactive metal can displace a less reactive metal from its salt solution. The reaction is often known as metal displacement reaction.
Some of the commonly used metals have been arranged in the decreasing order of reactivity. This is known as the reactivity series or activity series. The activity series of metals is an important concept in chemistry. The activity series of metals is an important tool for predicting the products of displacement reactions and the reactivity of metals in other reactions. Potassium is the most reactive metal, while platinum is the least reactive.
The higher the metal in the series, the more reactive it is and the more vigorously it reacts with water, oxygen and acid. A metal in the activity series can displace any metal below it in the series from its compound. The elements potassium, sodium, lithium and calcium are very reactive and they react with cold water to produce hydroxides and hydrogen gas. The elements magnesium, aluminium and iron are also considered as active metals and they react with steam to produce oxides and hydrogen gas. The metals above hydrogen are more reactive than hydrogen. These metals can displace hydrogen from acids or water and liberate hydrogen gas. The metals copper, silver gold and platinum are less reactive than hydrogen and they do not replace hydrogen from water or acid.
Examples for metal-displacement reactions:
- Zinc can displace copper from copper sulphate solution and iron from ferrous sulphate solution. So zinc is more reactive than iron and copper.
If a piece of zinc metal is added to aluminium sulphate solution, no reaction takes place. So aluminium is more reactive than zinc.
- If small pieces of copper are added into solutions of zinc sulphate, aluminium sulphate and ferrous sulphate, no reactions take place. So, copper is less reactive than zinc, aluminium and iron.
- Aluminium can displace Zn from zinc sulphate solution, Cu from copper sulphate solution and Fe from ferrous sulphate solution.
- Iron displaces Cu from copper sulphate solution, but it does not displace Al and Zn from their salt solutions.
Not only metals but also non-metals can take part in displacement reactions.
For example, chlorine gas displaces bromine from potassium bromide solution. The solution of potassium bromide acquires a yellowish and orange color of the liberated bromine gas.
- Students understand the terms like metals, metal displacement reaction, reactivity series, etc.
- Students acquire skills to perform & visualize the reactions of Al, Zn, Fe and Cu with the following salt solutions
- Aluminium sulphate
- Zinc sulphate
- Ferrous sulphate
- Copper sulphate
- Students can analyze the meaning of reactivity series of metals based on the inferences from the experiment.
- Students acquire skills to perform an experiment to determine the reactivity of metals in salt solutions.