Certified Transport Registered Nurse Certification Practice Exam

Which gas law explains the principle behind the rising and falling of a hot air balloon?

1. Henry's Law

2. Charles' Law

3. Graham's Law

4. Boyle's Law

The correct answer is: Charles' Law

The principle behind the rising and falling of a hot air balloon is explained by Charles' Law. This law states that the volume of a gas is directly proportional to its temperature when pressure is held constant. In practical terms, when the air inside the balloon is heated, it expands, leading to an increase in volume. This expansion results in the air becoming less dense than the cooler air outside the balloon. The difference in density creates lift, allowing the balloon to rise. Conversely, when the air inside the balloon cools, its volume decreases, making the air inside denser than the surrounding cooler air. This density difference causes the balloon to descend. Thus, Charles' Law is essential for understanding how temperature changes of the air inside the balloon directly affect its ability to rise or fall through the atmosphere.