How important is the sense of smell?
Your sense of smell guards you from eating rotten foods, conjures up memories from the past, gives you a stronger sense of place, helps you to find a mate, connects you with a newborn baby or a pet, and offers you comfort during a Thanksgiving meal or in a house with freshly baked apple pie! I’d say it’s pretty darn important!
The biology and the chemistry of smell are active fields of study as they have long been misunderstood. Many theories have come and gone regarding how the sense of smell works, with the prevailing theory being the receptor site theory, and for students of chemistry, there are some neat relationships between smell and the chemical compounds that make up substances.
T
his mini-unit on the chemistry of smell provides students the opportunity to explore how the makeup of an organic molecule can be an indication of how that substance will smell!
What Are the Categories of Smells?
The students explore the fragrance and/or molecular formula and chemical name of 21 household substances and food products. Cooperative smelling and taste testing are fun engagement activities that help students to get motivated to describe and categorize smells. The categories distill down to: sweet/fruity, minty/medicinal, earthy, fishy, and putrid.
Students look for patterns in the chemical names and molecular formulas of 12 different substances and then they learn how those substances smell, which provides more information in which to look for patterns! Five mystery molecules will need to be identified based on the pattern framework that students have discovered. Students make educated 
guesses about the mystery smells and then they actually smell them to see if they were correct!
Your students will learn how to properly ‘waft’ to smell anything in the science lab, and they will develop an appreciation for their sense of smell. Teachable moments arise as students disagree about how they would describe a scent or discover that some people simply cannot smell certain scents! Two optional projects will allow students to further explore these and other interesting questions related to the biology of smelling and the chemistry of smells!
What Standards Does this Activity Engage?
These lessons incorporate the NGSS crosscutting science concepts of patterns, structure, and function and the engineering practices of developing and using models, analyzing and interpreting data, and the concept that scientific knowledge is based on empirical evidence. This lesson series aligns with the NGSS Standard MS-PS1.1 (Develop models to describe the atomic composition of simple molecules and extended structures) and the DCI MS-PS1.A (Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.).
What Preparation is Necessary?
The necessary materials include: cotton balls and black film canisters or vials, Jelly Belly jelly beans, and small amounts of the following: vanilla extract, vinegar, almond extract, lime juice, peppermint extract, mushroom, honey, camembert cheese, Vick’s Vapor Rub or Bengay, canned anchovies or sardines, apple juice, canned tuna, dirt, nail polish remover, eucalyptus oil, and butyric acid.
In addition to preparing the film canisters with the various scents, to prepare this activity you will need to print and cut apart the molecule cards, the smell category strips, and the mystery molecule cards. Paperclip the card types separately and color-code or number them as sets (for those inevitable wandering pieces!). Store the sets in sandwich bags. Students start the pattern sniffing with just the molecule cards and receive the others cards later.
Try this lesson series to tie together units in properties of matter and chemistry, biology and chemistry, or to introduce organic chemistry! Or just try during a fun week at the end of the year!
Check out the lesson series HERE!
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