How are bubbles formed in boiling water?

Bubbles in boiling water 
How bubbles are formed in boiling water ?

Whether cooking sausages, eggs or tea
We can always see how air is released from water.

At room temperature, there is always some air dissolved in water. The colder the water, the more air is dissolved. Air becomes less soluble in water as the temperature rises. When the water boils the air is released in the form of bubbles. Two thousand years ago, an attempt was made to use the power of steam with Heron's ball, but the great breakthrough came only with the steam engines. The steam engine improved by James Watt is the most well-known. A little later the steam engines were used to drive locomotives and paddle steamers-the modern steam turbines followed later.