Minnesota Boiler License Practice Exam

When pressure increases on steam from a given amount of water, what happens to its volume?

1. Increases

2. Decreases

3. Remains the same

4. Increases temporarily

The correct answer is: Decreases

When pressure increases on steam from a given amount of water, its volume decreases because of the physical principles governing gases and steam behavior. This relationship is particularly described by the ideal gas law, but it is also influenced by the properties of steam as it behaves more like a fluid under high pressure. In a closed system, increasing the pressure applied to steam forces the molecules closer together, effectively compressing the gas. While steam is generated by heating water, it has a significant volume, but when that steam is subjected to higher pressures, it occupies less space as the energy of the molecules is utilized in overcoming the increased pressure rather than expanding the volume. Thus, as the pressure rises, the overall volume of the steam decreases. The concepts of thermodynamics, specifically regarding the behavior of gases under varying pressures and temperatures, clarify that for steam in a closed environment, increased pressure typically leads to a reduction in volume, consistent with the laws governing gas behavior under compression. This is why the correct understanding indicates that the volume decreases as pressure increases.