Activity: Amazing Aromas

By Susan Hershberger

Safety Suggestions

• Safety goggles required
  
• Do not eat or drink any of the materials used in the science part of this activity
• Thoroughly wash hands after this activity

Disposal: Neutralize all solutions before pouring down the drain. Wash reusable items with soap and water. Disposable items, such as zip-closing plastic bags, may be disposed of safely with the household trash or recycling.
Note: Cover your workspace and protect your clothing to avoid unwanted stains from the insect dye.

Introduction

Insects help plants get pollinated, so that they can make seeds. Insects do not really know they are doing this valuable job for plants, because their focus is on looking for food, such as nectar from flowers. How do plants attract the insects and get their help? It is mostly from the scent, color, and shape of their flowers. In this activity, you will assemble some common aromas from natural fruits and flowers and from products that use scents (which may be artificial) as part of their ingredients. Using just your sense of smell, can you identify the source, and match the real aroma to the aroma in specific products? It’s not easy!

Materials

• 3 Scented items such as candles, soaps, or lotions. You could also use candies, beverages, or dessert mixes that contain common fruit flavors.
  
• 3 Corresponding real, natural items. For example, if you find a vanilla candle, use natural vanilla extract. If you find rose-scented shampoo, find a real rose from a rose plant. If you find an orange candy or gelatin mix, find a small piece of real orange. If you find strawberry lotion, get a real strawberry.
• 6 Small jars, containers, or cups that are hard to see though. Paper can be taped on the outside.
• Assistant to help you
• Scarf or bandana to use as a blindfold
• Small amount of warm tap water (optional)

Procedure

Prepare your samples

1. Put a small amount of each scented product in three of the small cups or containers. Put a small amount of each natural product in each of the other three small cups. Make sure the contents are hard to see, but keep the containers open to allow the odor to be detected.
2. Check if you can detect the aroma by gently waving or fanning the cup under your nose. Chemists call this technique wafting. This is a safer way to sample the aroma than putting your nose in a jar and taking a big sniff.
3. If you cannot detect any aroma, possibly because a candy has a hard shell, you can cut the sample into small pieces and even add a little warm water to the cut pieces. The warm water helps the aroma molecules turn into a gas or vapor so your nose can detect the aroma.
4. Once you have detected the odor of each of the of three scented products and the corresponding natural items in cups, you are ready to test both the products and your sense of smell.

Test the real aroma and the aroma in products

1. For the fairest test, wear a blindfold.
2. Ask your assistant to gently wave, under your nose, the containers with the samples.
3. Your first job to guess which aroma you are detecting. Ask your assistant to write down words you used to describe each aroma.
4. Second, try to guess whether you are detecting the natural aroma, or if the aroma is in a product.
5. Since you are blindfolded, your assistant can write your response down in the data table.
6. Repeat the same process with the other samples, going in any order.
7. Can you tell which samples have the same aroma? Tell your assistant which are pairs. It is OK to ask to go back to smell a previous sample.

What did you observe?

Observation Table

How does it work?

The aromas of flowers and fruits are chemical compounds made of different combinations of several elements — mainly carbon, hydrogen, and oxygen. The aroma of each substance is a direct result of the way the atoms are arranged and grouped together. Different arrangements of these same elements make up the different aromas. These compounds become gases easily, which allows them to be detected by our sense of smell. Bees and other pollinators detect these aromas, too! 

It is very important for insects to be able to identify the correct scents and shapes so that they can navigate to the correct flowers. Otherwise, they will not be successful in pollinating the flowers. Luckily, insects have very accurate sensory organs and are able to find the right flowers. 

You were faced with the challenge of identifying natural odors, but also trying to separate them from their artificial versions. Chemists work very hard to make artificial flavors and odors as close to the natural ones as possible. For example, natural vanilla flavor is expensive, so scientists try to copy the aroma or flavor with imitations for specific products such as candles, soaps, and even foods like vanilla ice cream. The same is true of many other scents and flavors. Manufacturers will often use an artificial version of a taste or odor because they are cheaper and easier to control and use. 

Hopefully you now have a better idea what it is like to be a bee trying to find the perfect flower to pollinate. Maybe you’ll also have a better appreciation how complex and wonderful our natural world is!

Susan Hershberger, Ph.D. is Director of the Center for Chemistry Education at Miami University in Oxford, OH.