In a typical combustion reaction, water is released as a gas, specifically as water vapor. Combustion reactions involve the rapid combination of a fuel with oxygen, resulting in the release of energy in the form of heat and light. When hydrocarbon fuels, such as methane (CH4) or gasoline, undergo combustion, they react with oxygen (O2) from the air. The carbon and hydrogen atoms in the fuel combine with oxygen to form carbon dioxide (CO2) and water vapor (H2O).
The water vapor produced in combustion is in the gaseous state due to the high temperatures reached during the reaction. As the combustion process occurs, the heat generated causes the water molecules to evaporate, turning them into a gas. This water vapor, along with other combustion products, is then released into the surrounding atmosphere.
However, it's worth noting that in certain combustion conditions where the temperature is low, incomplete combustion may occur, resulting in the production of soot or unburned hydrocarbons. In such cases, small liquid water droplets, known as aerosols, can be formed along with the combustion products. These aerosols can eventually condense and appear as liquid water. But in the typical conditions of complete combustion, water is released as water vapor, primarily in the gaseous state.