When you blow on the back of your hand with your mouth wide open, your breath feels warm. But if you partially close your mouth to form an “o” and then blow on your hand, your breath feels cool. Why?
Solution 11DQ Step 1 of 3: When we blow on the back of our hand with our mouth wide open, our breath feels warm. Because, the body temperature is different from the surrounding. Step 2 of 3: Whereas if we partially close our mouth to form an “o” and then blow on our hand, our breath feels cool. Because when we close our mouth to form “o”; the air inside the mouth is forced through a smaller opening and then expands. The process is similar to the concept used in case of refrigerators. Air is compressed and then allowed to expand causing cooling.