| Chemical Properties |
Water is a stable but an active compound. It undergoes many kinds of reactions.
The action of heat: Water is very stable in ordinary conditions. It decomposes into hydrogen and oxygen only at a very high temperature and that too to a very small extent. At 27000C, only about 10% of a sample of water is decomposed. |
The action of metals: Metals vary widely in their action on water. Some act vigorously, some mildly and some do not appear to act at all. Like hydrogen, metals also have a tendency to lose electron(s) and be converted into positive ions. So they are said to be electropositive. Metals, along with hydrogen, may be arranged in decreasing order of their tendency to lose electron(s). The arrangement is known as the activity or the reactivity series. It is also called the electrochemical series.
When a metal is added to water, there are two electropositive elements - the metal and the hydrogen already present in water. These electropositive elements compete with each other for the negative oxygen or hydroxide group in water.
Metals placed higher than hydrogen in the reactivity series have a greater tendency to form positive ions than hydrogen. So they will displace hydrogen from water and acquire the negative oxygen or hydroxide group. Also, the higher the metal in the reactivity series, the more vigourous should be its action on water. Elements below hydrogen in the reactivity series do not displace hydrogen from water. Lead, which is placed higher than hydrogen, also does not displace hydrogen from water.
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