Question

When calcium metal is added to water, the gas evolved does not etch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?

Answer 1

Sodium reacts at room temperature as it is the most reactive metal and tends to donate electron with every other element. When Na is added to H2O it catches fire and forms NaOH (sodium hydroxide). When calcium metal is added to water, the heat evolved is not enough for the gas to catch fire. H2 is flammable but due to less amount of heat the gas bubbles do not escape but start floatin along with calcium forming Ca(OH)2

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