Putting candles on a birthday cake is a tradition that has been around for a long time.
We make a wish on our birthdays by blowing off the flame on the candles.
To blow out the flame, what we do is we breathe in and then blow out the air towards the flame.
Similarly, we also blow on a cup of hot coffee to cool the coffee down.
The process of cooling by blowing air onto it depends on the surface area of the material.
For example, when the coffee is in a cup, the surface area of the coffee exposed to the surroundings is less.
When we blow air onto it, the coffee does cool down but it takes some repeated blowing as well as time.
However, when we pour the coffee into a saucer, the surface area of the coffee exposed now increases.
The process of cooling now occurs much faster and effectively when we blow air onto it.
Therefore, the surface area of the material exposed to air decides how fast and effective the cooling is.
And We often use our mouth to blow air to serve some purposes.
A warm cloth on a red-itchy eye provides us comfort
In order to make the cloth warm, we often blow air onto the piece of cloth.
Many a time, we also whistle by blowing air from our mouth.
We also clean mildly dirty objects by blowing air onto it, like our spectacles.
Blowing air onto the palm of our hands help us keep warm on a chilly day.
So we can conclude that we can blow air to serve different purposes.
We blow air by breathing in and then releasing the air in a particular direction.
We blow air through our mouth to cool extremely hot food, to warm our hands during winter, to clean our dirty spectacles..etc