system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why we can blow hot or cool air just by changing the shape of our mouths.
gpt
You can only blow hot air.  However, when you purse your lips and blow, the narrow opening causes the air to speed up, and faster airflows are better at pulling in surrounding air.  So that air that you're feeling in that case is partly air from your lungs, and partly cooler air from the surrounding environment.

Try loosely cupping your hands around your mouth and blowing, and you'll see that the temperature is the same when you're blocking the airflow off from the surrounding, cooler air.