Thursday, February 13, 2014

Seeing Your Own Breath

It's quite possible that your kids will ask you (or have already asked you) why they can see their own breath at times.  As you're likely aware, it's very common to see your own breath when it's very cold outside.  Kids may think they are breathing out smoke or making some sort of cloud, but what's really going on?

When you breath out air from your lungs, there's a concentration of water vapor in this air.  The air that comes out of your lungs on a cold day is much warmer than the surrounding air.  The energy from the warm air transfers to the cold air.  The air that just leaves your lungs quickly drops in temperature.  As the air drops, the water vapor goes through a phase change from a gas to a liquid.  The water vapor changes into very tiny droplets of water.  These very tiny droplets of water, when viewed as a collection, look like a cloud of air leaving your mouth.

Although it would be more exciting if you could breath fire, that's not the case here.  It's a simple phase change of water from a gas to a liquid.

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