Final Answer:
When water boils, it undergoes a phase transition from a liquid to a gas. The process of boiling involves the absorption of heat energy, which causes water molecules to gain enough kinetic energy to break the bonds holding them in the liquid state. As these molecules escape into the gaseous phase, the substance released is primarily water vapor. The correct answer is c. water vapor.
Step-by-step explanation:
When water reaches its boiling point, it undergoes a phase transition from a liquid to a gas. The process of boiling is characterized by the absorption of heat energy, causing water molecules to gain enough kinetic energy to break their intermolecular bonds and transition into the gaseous state. The substance that is released during this phase transition is primarily water vapor.
Water vapor is composed of individual water molecules in the gas phase. It is invisible when in a pure form, but it becomes visible as steam or clouds when it condenses into tiny droplets in the air. The release of water vapor during boiling is a fundamental aspect of the water cycle, where water evaporates from bodies of water, forms clouds, and eventually precipitates as rain or other forms of precipitation.
The other options—carbon dioxide (a), oxygen (b), and nitrogen (d)—are not released during the boiling of water. Carbon dioxide is a gas, but it is not a significant component of pure water. Oxygen is also a gas but is not a product of water boiling. Nitrogen is a major component of the Earth's atmosphere, but it is not released during the boiling process.
In summary, when water boils, the primary substance released is water vapor, making option c, water vapor, the correct answer.