To convert 1 lb of water at 212 °F into steam at atmospheric pressure, how many BTUs are needed?

To convert 1 pound of water at 212 °F (the boiling point of water at atmospheric pressure) into steam at the same pressure, it's essential to understand the concept of latent heat. The process of turning water into steam requires a specific amount of energy called the latent heat of vaporization, which represents the energy needed to change a substance from liquid to gas without a change in temperature.

For water, the latent heat of vaporization is approximately 970.3 BTUs per pound. This is the energy required to take 1 pound of water at 212 °F and convert it fully into steam at the same temperature and pressure. The high value reflects the amount of energy needed to break the molecular bonds that hold water in its liquid form, allowing it to transition to steam.

Other options suggest amounts of energy that are significantly lower or higher than the actual requirement, which would not effectively complete the phase change from water to steam at the specified conditions. Thus, the correct amount of 970.3 BTUs accurately represents the energy needed for this process, making it the correct answer.