AIR FRESHENER

Materials:

Glass jar
Plastic wrap
Ribbon
Unflavored gelatin – 4 scant T.
1 c. very hot water
1 c. cold water
2 T. salt
Spoon
Food coloring
Scent
Foam stickers

Procedure:  Please see video.

Science: The molecules we perceive as smells are called “odorants.” Odorant molecules stimulate sensory nerve cells (neurons) at the top of the nasal cavity and these respond by sending impulses to the brain. These neurons are very small - there are at least 10 million of them in your nose! There are hundreds of different odor receptors, each with the ability to sense certain odor molecules. Research has shown that an odor can stimulate several different kinds of receptors. The brain interprets the combination of receptors to recognize any one of about 10,000 different smells.

Our sense of smell is stimulated by molecules in a gas form. The molecules may come from the air we breathe or from substances released in our mouth when we eat. The ability to smell and taste go together because odors from foods allow us to taste more fully. In other words, you can’t really taste anything without some help from your nose! Take a bite of food and make note of how it tastes. Now hold your nose and take another bite. Is there a difference? You can only smell odors when they are a gas form. Materials that release virtually no vapor, such as ionic salts, are odorless. Different molecules get into the air, or evaporate, at different rates. Also, some molecules have a stronger smell than others.

Perfume is made from molecules that get into the air easily and have a strong smell. The molecules from the peppermint candy also have a strong smell.

Skunk spray contains smelly sulfur compounds called thiols, which our nose can detect in tiny concentrations. If thiols make up just a few billionths of the volume of air and other gases in a room, we can smell them. A different kind of sulfur thiol is actually added to natural gas (which is itself odorless) so we can easily smell a gas leak.

Scientists believe the way something smells depends on its molecular structure. For example, things that smell fishy are generally made up of amines containing a nitrogen atom bonded to three other atoms and having a non-bonding pair of electrons. The molecular structures of several minty materials also reveal some similarity. However, very subtle differences in structure can produce different odors.

Smells are very important to businesses. For example, companies that sell cookies, bread, perfume, shampoo, wine and coffee spend billions every year making sure their products smell good to the rest of us.

Lingering question that has troubled Miss Mary since she was 10 years old:  why can't we invent Smell-a-Vision?