To study the reaction of metals with water under different temperature conditions.
Elements are classified into two basic categories, metals, and non-metals.
In chemistry, a metal is defined as an element which can form positive ions by losing electrons i.e., they are electropositive elements. Examples of metals include sodium, magnesium, potassium, aluminium, copper, silver, iron, lead, zinc, nickel, etc. Metals are characterized by their chemical and physical properties, such as malleability, ductility, ionization and bonding properties, etc.
Metallic elements usually have 1, 2, or 3 electrons in their outer shell. The smaller the number of valence electrons, the more active the metal. They form cations by losing electrons. The metal molecule in the vapor state is generally monoatomic. They generally form basic oxides. They ionize by losing electrons, that is why they are called reducing agents. Some metals react with water to form metal hydroxides or oxides and produce hydrogen gas. General equation for the equation is,
Metal + Water → Metal hydroxide + Hydrogen
Different metals react with water at different rates. Most of the metals do not react with water. However, alkali metals react vigorously with water.
Cold Water |
Sodium, potassium and calcium readily react with cold water, to produce hydroxides. |
Hot Water |
Magnesium does not react with cold water, but reacts with hot water to produce hydroxide. |
Steam |
Zinc and aluminium react only with steam, to produce oxides. Iron's reaction with cold water is very slow and can take days. But when iron reacts with steam, then iron oxide is formed. |
The reaction between sodium and water is highly vigorous. When sodium reacts with water, sodium hydroxide and hydrogen are produced. This reaction is highly exothermic. So much heat evolves during the reaction that the reaction mixture catches fire.
2Na(s) + 2H2O (l) → 2NaOH(aq) + H2 (g)
Note: Due to its strong reactivity, sodium is kept under kerosene when being stored to prevent it from reacting with any possible atmospheric moisture. This is done to avoid any accidental fire.
When potassium reacts with water then potassium hydroxide and hydrogen gas are formed. Lot of heat is produced during this reaction.
2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)
When calcium reacts with water, then calcium hydroxide and hydrogen gas are produced. This too is an exothermic reaction. When bubbles of hydrogen gas stick to metal then calcium starts floating.
Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g)
Magnesium does not react with cold water. It reacts with hot water and forms magnesium hydroxide and hydrogen gas. It also starts floating due to the bubbles of hydrogen gas sticking to its surface.
Mg(s) + 2H2O (l) → Mg(OH)2(aq) + H2(g)
When steam is passed over magnesium, the reaction becomes fast. Magnesium oxide and hydrogen gas are formed, in this reaction.
Mg + H2O → MgO + H2
Aluminium does not react with cold or hot water. But when steam is passed over aluminium, aluminium oxide and hydrogen gas are produced.
2Al(s) + 3H2O(g) → Al2O3 (s) + 3H2 (g)
Zinc does not react with cold or hot water. Zinc metal produces zinc oxide and hydrogen gas when steam is passed over it.
Zn + H2O → ZnO + H2
Reaction between iron and cold water too slow to be noticed. When iron reacts with atmospheric moisture, it forms rust (iron oxide). But this is a very slow reaction.
When steam is passed over iron then iron oxide and hydrogen gas are formed.
3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2 (g)
