The conversation between human and AI assistant.
Why is ice lighter than water?
That makes sense. But why does water expand as it freezes?
Water expands as it freezes because of the way the hydrogen bonds form between the water molecules. Unlike most substances, water molecules become less dense as they get colder, which means they take up more space. As the water approaches freezing point, the molecules start to form ice-like structures, which push the molecules farther apart and cause the water to expand.