system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the air that you exhale warm when your mouth is open wide while it's cooler when you blow the air through pursed lips?

I feel like it may have to do with the tongue because I can feel a slight difference if I change my tongue placement in my mouth, but I'm not completely sure.

Or is it due to speed of exhalation?
gpt
Contrary to what people in this thread are saying, this has nothing to do with the speed of the air, improved convection or wind chill. When you exhale onto your hand with your mouth open, most of the air that hits your hand came from your lungs. Conversely, blowing through pursed lips forms a narrow stream of air from your lungs which drags cool air from the surrounding atmosphere with it.

Edit: this effect is called entrainment.