If the air temperature is increased from 55 to 75 degrees Fahrenheit, how does the moisture capacity of air change?

When the air temperature is increased, its capacity to hold moisture increases significantly. This is due to the fact that warmer air can hold more water vapor compared to cooler air. Specifically, for every increase of approximately 20 degrees Fahrenheit, the moisture-carrying capacity of air approximately doubles.

In this scenario, increasing the temperature from 55 to 75 degrees Fahrenheit represents a 20-degree increase. Therefore, the correct interpretation is that the moisture capacity of air almost doubles. This understanding is key in HVAC systems where controlling humidity levels is essential for comfort and maintaining air quality.

The other options do not accurately reflect the relationship between temperature and moisture capacity. For instance, stating that the capacity decreases or remains the same would overlook the fundamental principle of thermodynamics that governs how air holds moisture. Similarly, saying it triples would overstate the change in capacity associated with just a 20-degree increase. Thus, recognizing that the moisture capacity of air almost doubles with this specific temperature change is essential for understanding HVAC system design and operation.