Assume a baker of pure water has been boiling for 30 minutes. What is in the bubbles in the boiling water?
Answer: water vapor. WHY?
This is becuase inside the bubbles there is no water and therefore contain gas called water vapor.
To understand what is in the bubbles in boiling water, we need to understand the process of boiling and the properties of water.
Boiling occurs when the temperature of a liquid reaches its boiling point, which is 100 degrees Celsius or 212 degrees Fahrenheit for water at sea level. When water reaches its boiling point, the heat energy causes the water molecules to gain enough energy to overcome the intermolecular forces holding them together, and they start to change from a liquid state into a gaseous state.
As water molecules gain energy, they start to move faster and become more energetic. Eventually, some of the water molecules at the surface of the liquid gain enough energy to break free from the liquid and escape into the air. These escaping water molecules form bubbles, which rise to the surface and release water vapor into the air.
Therefore, the bubbles in boiling water consist of water vapor, which is the gaseous form of water. The water is evaporating and transforming into a gas due to the heat applied during the process of boiling.