TeXes Science Practice Test

How does breathing demonstrate the principles of gas behavior?

1. It balances temperature

2. It changes volume and pressure

3. It alters chemical composition

4. It impacts humidity levels

The correct answer is: It changes volume and pressure

Breathing illustrates the principles of gas behavior primarily through the relationship between volume and pressure, as described by Boyle's Law. When a person inhales, the diaphragm and intercostal muscles contract, causing the volume of the thoracic cavity to increase. According to gas behavior principles, when the volume of a gas increases, its pressure decreases. This decrease in pressure creates a vacuum that allows air to flow into the lungs. Conversely, during exhalation, the diaphragm and muscles relax, reducing the thoracic cavity's volume. This leads to an increase in pressure within the lungs, forcing air out. This interaction between volume and pressure during the respiratory cycle provides a clear and practical demonstration of gas laws in action. While other options mention relevant aspects of gas behavior, they do not directly illustrate how breathing specifically relies on the interplay of volume and pressure.