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Now You Smell It,
Now You Don't

Starring

You and Your Students!

Script By

Vicki Cobb, Education World Science Editor

Synopsis

Take a few deep breaths instead!

Genre

The Senses, Human Body

Props Required

• 2 small containers
• vanilla extract
• ground cinnamon
• measuring spoons

Setting the Scene (Background)

Have you ever noticed how bright the light is when you emerge from a movie theater during the daytime? After a few minutes outside, the daytime light does not seem so strong. You might have noticed a similar sensation in the bathtub. Does that hot bath feel so hot after a while? Or does the volume of the TV seem louder in the morning than it did the night before? As your nerves are stimulated by light, temperature, or sound, they adapt. The stimulus becomes less apparent. Of all the senses, the fastest adapting one is your sense of smell!

Stage Direction

This experiment should be done by students working in pairs.

The Plot

Show-Biz Science is scripted by popular children's book writer Vicki Cobb. Click to learn more about Vicki or to read a brief synopsis of her philosophy of teaching science. Visit our archive of archive of Show-Biz Science Activities. Watch for a new activity each week! Then chat with Vicki -- share your feedback and ask your questions about teaching science -- on our special Showbiz-Science message board. Be sure to visit Vicki's Kids' Science Page for more great science fun, a complete list of her books, and information about how you can invite Vicki to come to your school!

Act I

• In one container, mix 1 tablespoon of ground cinnamon with 4 tablespoons of vanilla extract.
• In the other container mix 1 tablespoon of ground cinnamon with 4 tablespoons of water.
• Sniff the cinnamon-vanilla mixture until you can't smell it any more. It will take at least six sniffs.
• Then immediately sniff the cinnamon-water mixture until you can't smell it.
• Immediately sniff the cinnamon-vanilla mixture again.

The second time you smell the cinnamon-vanilla mixture it should smell different from the first time. This time it will smell more like vanilla than cinnamon.

Here's What Happened
When you sniffed the cinnamon-vanilla mixture, you tired out the nerves that respond to both smells. Then when you sniffed the cinnamon-water mixture, you only tired the nerves that respond to cinnamon. When you returned to the cinnamon-vanilla mixture, the nerves that smell vanilla had recovered while the nerves that smell cinnamon were still tired. As a result, the mixture smelled as if it was mostly vanilla.

This experiment shows that there are different nerves for different kinds of smell.

The End

There are all kinds of examples of smell adaptation in daily life. The smell of lunch is very obvious when you first enter the cafeteria. Take a deep breath and inhale the aroma. How many breaths do you need to take before you can no longer smell the aroma no matter how much you sniff?

What is your reaction to the smell of rotten garbage? Do you hold your breath? Ask a garbage man about the smell of garbage. Does it bother him, or is it not so bad? What do your students think about all the money that's spent on perfume and making stores smell good? How long does the effect last?

Find more experiments for teaching about the sense of smell in Vicki Cobb's book, Follow Your Nose, Discover Your Sense of Smell.