What are the bubbles that appear in boiling water? - P4-G

In Science, P4-G started a new unit, "The Changing States of Water" and have already begun conducting experiments. In their first experiment, students investigated what happens when water is heated continuously. How does the state of water change? What can we see inside the beaker? Students observed bubbles appearing and growing in size as the temperature increased. In their second experiment, students investigated these bubbles were. Students did this by observing what came out of a hole in the lid of a beaker of boiling water. Next they held an empty test tube over the hole and observed what appeared on its surface. Finally, they placed a new empty test tube inside the beaker.