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Eureka! Mirror, Mirror in the Steam

Note:  This is the part of a series of posts about science activities to be done in the bathroom – the lav-oratory if you will.  The following is adapted from this book.

image002Have you ever stepped out of a nice hot shower ready to comb your hair or brush your teeth only to be confronted by a steamed up mirror?  When you take a hot shower or bath, you might notice clouds of steam in the air. The water is so hot that it changes from water (a liquid) to steam (a gas). This is called evaporation. When this steam hits your cold mirror it turns back into water. This is called condensation. If you look really close at the steamed up mirror you will see that it is just teeny tiny drops of water all over the mirror. These tiny drops make it hard to see yourself in the mirror so you don’t brush your nose instead of your teeth.

One way to keep your mirror from steaming up (and keep toothpaste out of your nose) is to keep it warm enough that the steam doesn’t condense back to water. Or you can put something on the mirror so that the water doesn’t bead up into tiny drops when it condenses. Certain chemicals, like glycerin, mix with water really well and are called hydrophilic (hydro means water and philic means to like). This causes the water to spread out over the mirror so that you can still see yourself. Other chemicals, like oil, do not mix at all with water and are called hydrophobic (hydro means water and phobic means to fear).

Explore some ways to keep your mirror clear!  Below is a list of items to try rubbing on your mirror to keep the steam from beading up on your mirror when it condenses.  After you rub these on different parts of your mirror (make sure you keep track of what was used where!), use a paper towel to polish the mirror back to a nice shine.

  • Shaving Cream
  • Bar of Soap
  • Liquid hand soap
  • Dishwashing Soap
  • Car wax
  • Shampoo
  • Toothpaste (without baking soda as that will scratch your mirror)
  • Inside of a Raw Potato (scuba divers swear by this)

Other questions you can investigate are

  • How long does it take the steam fighting power to wear off?
  • Do different brands of soap etc. work better than others?