What happens to water when it bubbles?

Why does boiling water bubble?

Whether in the kettle or in the pot: As soon as water is brought to the boil, it hisses and bubbles loudly. Of course, the rising air bubbles are the cause of the background noise. But the noises only arise when they "dissolve into thin air" again.

Water molecules jump out of the pot

Water consists of innumerable tiny particles, the water molecules. For physical reasons they are always in motion. Therefore, even at room temperature, some of them repeatedly jump out of the pot and become gaseous. They say: the water evaporates.

Heating is accelerated evaporation

If water is heated in the pot, this process is accelerated. When the water temperature approaches 100 degrees, the water molecules no longer only jump away from the surface of the water. They also become gaseous at the bottom of the pot and first rise as small water vapor bubbles. The water is now boiling.

First it hisses

Water vapor bubbles form at the bottom of the pot, as this is where the temperature is highest. We associate boiling with a hissing noise. This occurs because the steam bubbles rise to areas where it is still too cold for the steam. Therefore they collapse again and the loud hissing arises.

At 100 degrees it bubbles

When the water finally begins to boil at 100 degrees Celsius, the steam bubbles rise to the surface of the water and burst there with a loud noise, but the sound is now more bubbling than hissing. By the way, if you take a closer look you will notice that the water vapor bubbles get bigger and bigger as you rise. This is because the water pressure on the surface of a pot is lower than that on the bottom of the pot. The vapor bubbles can therefore expand more and more towards the top.