Ask a Question
or
Create a Poll
  1. Home /
  2. Questions /
  3. Science

by PokerPaul on August 1st, 2005

PokerPaul

Question

Help answer this question below.

Why do we blow on our hands to warm them up but blow on our tea to cool it down?

Share:
Other

Answers. Showing one answer.

  • by Encyclopedia_John on August 9th, 2005

    Encyclopedia_John

    Try the following experiment:

    1 - Blow with your mouth wide open. Your breath will come out hot and slow. That's how you blow on your hands to warm them up.

    2 - Blow with your mouth barely open, as if you were whistling. Your breath will come out cold and fast. That's how you blow on your food to cool it.

    To really explain the difference between these two cases, I would have to get into a lot of technical details about the science of thermodynamics, specifically the law of conservation of energy, an energy equation of fluids called the Bernoulli equation, the ideal gas law, and the concept of "entropy". I think to cover all that would be too long of an explanation.

    To give a simple but accurate answer: when you force your breath through an opening, some of its internal energy (heat) is converted into kinetic energy (speed) and some of its internal energy is lost in interacting with the opening. Losing internal energy means that the temperatue of the air will drop. The smaller the opening, the greater the temperature drop.

    Comments
    • Like
    • Report

    No comments. Post one | Permalink

Want to attach an image to your answer? Click here.

Did this answer your question? If not, then ask a new question or create a poll.

More Questions. Additional questions in this category.

You're reading Why do we blow on our hands to warm them up but blow on our tea to cool it down?

Follow us on Facebook!

Related Ads

Related Questions

Professionally Researched

Answerbag

a Demand Media company