Why is it Cold When You Get Out of the Shower?

This is a question my 5 year old wants an answer to.  The other day she gets out of the shower, but refuses to dry herself off because to do so would mean moving the towel she currently has wrapped around her to keep her warm.  I tried telling her that by drying herself off she will feel warmer.  She wasn't buying into the argument, however.

So why is it cold when you get out of the shower?  There are a couple of major reasons:

1.  While in the shower, presumably you have the hot water running.  Energy always transfers from the warmer object to the cooler object.  In this case, the warmer object is the water, and the cooler object is the surrounding air.  Since energy is transferred to the air in the shower, the surrounding air becomes warmer.  Once you walk out of the shower, the new air you've entered is at a lower temperature.  This is especially true if you open the bathroom door.  Energy from the warmer air inside the bathroom transfers to the colder air outside the bathroom and it very quickly feels colder inside the bathroom.

2.  The second reason is evaporation.  Evaporation is a cooling process.  This is one of the reasons we sweat when we're working out.  The beads of sweat evaporate and cool our bodies.  Evaporation is a cooling process because energy is leaving your body and transferring to the air.  After stepping out of the shower, the beads of water that remain begin to evaporate, thus cooling your body.  You can quicken this process by drying your body with a towel.  This acclimates you to the surrounding air temperature more quickly and you feel warmer.

I don't think my daughter believed me when I told her drying off would make her feel warmer more quickly.  She pouted for awhile.  Sorry little one, physics is the law!  :-)