Smell and Humidity

Materials Needed:

salt
pepper
dust
your hot water faucet
other things that smell

Procedure 

Lets begin with some pepper.  Sprinkle some pepper onto your hand.  Hold it about a foot from your nose and sniff gently.  Do you smell the pepper?  If not, move it a little closer and try again.  Be careful not to sniff the pepper up your nose, as that is very unpleasant. 

Now lets try it again, but this time go to the sink.  Turn on the hot water and let it run until it gets nice and hot.  Leave the water running and place your hand above the sink.  Now sniff the pepper again, starting at least a foot away.  You should find that you the smell of the pepper is much stronger and can be smelled farther away.

Try this again using salt instead of pepper.  Unless your nose is much better than mine, you will have to get VERY close (Read that as my nose in the salt) to smell the salt under normal conditions.  When I tried it with the hot water, I was surprised at how much stronger the smell was.

Why?  Several weeks ago, we saw that if your tongue is dry, you cannot taste things.  Some liquid is required to carry the flavor to your taste buds.  Our sense of taste and sense of smell are closely related.  The increased humidity in the air "wets" the molecules, making it easier for you to smell them.  The smell of the salt was in the air, wet or dry, but you needed the help of the humidity to smell it.

This also plays a part in the "smell of rain."  Searching the internet, this lead me on a merry chase.  I found references saying that this smell was due to everything from ozone produced by lightning (which you should smell after the storm, not before) to oils released by plants in response to changes in air pressure.  These to sometimes play a part, but most people seem to miss the impact of the suddenly increased humidity.

Go out and get some dust from the front yard.  Find a patch of nice, dry dirt and scoop up a little.  Smell it, just as we did with the salt and pepper.  Now take it inside and try it with the hot water running.  You should smell a very familiar smell which most people associate with rain.  Much of the smell that people call the "smell of rain" is actually the smell of dust in the air.  The increased humidity of the coming rain just suddenly makes the smell stronger, allowing you notice it.

This experiment  was re-printed with permission from Robert Krampf

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