Phy101 GDB Solution
Friday, January 21, 2011 Posted In PHY Edit ThisAt the moment in Pakistan, atmosphere is very chill. On one of such a chilly morning you can “see your breath”. Can you really? What are you actually seeing? Does this phenomenon depend on the temperature of the air, the humidity, or both? Explain.”
Solution:
The temperature of your body is 98.6 degrees fahrenheit. When you exhale, your breath is going from 98.6 degrees to the outside air, which, for all intents and purposes, is very low...say around 30 degrees fahrenheit (0 celsius).
Air at a colder temperature cannot hold as much water vapor in it as ai...
The temperature of your body is 98.6 degrees fahrenheit. When you exhale, your breath is going from 98.6 degrees to the outside air, which, for all intents and purposes, is very low...say around 30 degrees fahrenheit (0 celsius).
Air at a colder temperature cannot hold as much water vapor in it as air at a higher temperature. If you take an HVAC class, you will use psychrometric tables where you can graph how much humidity is in the air at a given temperature, dry bulb/wet bulb temperatures, etc.
Whatever the absolute (not relative) humidity is at that higher temperature, in order for it to NOT drop out of the air (turn to fog, which is 'seeing your breath') the air at that colder temperature must be able to contain that water vapor. This can be represented by a horizontal line on a psychrometric chart.
If the colder air CANNOT hold that water vapor, it literally drops out of its gaseous form and turns to a liquid, where it tries to disperse into the air around it (and go back to its gaseous state) or condenses on a surface (window, your face, etc).
This phenomenon depends on the temperature of the air, as higher temperatures can hold more water vapor than colder temperatures.
This phenomenon depends on the humidity of the air...if the absolute humidity is very low at the high temperature, the cold air will be able to handle the humidity without it dropping out of phase. If the absolutely humidity is too high for that lower temperature, it will drop out of phase.
