GCSE Chemistry Question Analysis Topic: Chemistry - Matter
Exam Question: When water is heated, we see bubbles rising up. Why?
Instead of a chemical reaction, boiling water results in a physical change. The water's molecules do not split into hydrogen and oxygen. Instead, the bonds that hold the water molecules together fall apart, allowing the substance to change state from a liquid to a gas.
The heat energy from boiling water is transmitted to the water molecules, making them move more quickly. After a while, the molecules have too much energy to maintain their liquid state. They create gaseous water vapour molecules as a result, which float to the surface as bubbles and move through the air.
End of analysis. Great!