Molecule Races

1. With a grown-up’s help, add about a quarter teaspoon of mint flavoring to each cotton ball using a measuring spoon or medicine dropper.


2. Put one cotton ball inside each balloon, being careful not to get any extract on the outside of the balloon.


3. Blow up the balloons (using a pump makes it easier) just enough so that they still fit in the boxes and are the same size, then tie them off. Place one balloon inside each box and replace the cover.


4. Place one box somewhere warm and the other box somewhere cool. For example, go outside and try a sunny spot vs. a shady spot, or out on a counter vs. in the refrigerator. Wait 5-10 minutes, then collect the two boxes.


5. Open up each box separately and smell inside. Which box has a stronger scent? Why do you think there was a difference between the warmer and cooler boxes?

Clean-up:

Throw balloons with cotton balls in the trash. Recycle or reuse covered boxes for another purpose.

You probably noticed that the scent was stronger in the box that was in the warm location. The temperature of a system affects how fast the molecules within the system are moving. In the warm location, the individual mint extract molecules evaporate from liquid to gas at a faster rate than they do in the cold location. Inside the warm box, there are more mint molecules in the gas phaseand they’re moving faster than the molecules in the cold box.The faster gas molecules are able to move, or diffuse, through the air and through the balloon into the box more quickly, giving a stronger mint smell.

In this activity, we discovered that it is possible to control the movement of gas molecules by controlling the temperature of their environment. Scientists also use temperature to manipulate materials at the atomic level, like super heating metal into a gas so it can be deposited on top of another material. These processes are used to invent new combinations of materials that don’t exist in nature. However, the tools that scientists use in the lab are really complicated, and sometimes involve dangerous materials. These tools must be used in a controlled environment, such as a clean room, where the air is carefully filtered. Since scientists can’t safely use most of their senses (like sense of smell) to determine the success of the process, they have to use other equipment such as microscopes to analyze their results.

Michael Shah and Albanie Hendrickson-Stives got hooked on materials science before they knew what it was. Find out what kinds of tools and techniques they use to make new materials that have never existed in nature.

Below are suggested alignment between this activity and concepts in the Next Generation Science Standards.

Performance Expectations

• MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.

Disciplinary Core Ideas:

PS1.A: Structure and Properties of Matter

Middle School

• Gasses and liquids are made of molecules or inert atoms that are moving about relative to each other.


• In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations.

Please click on the PDF below for a more detailed description of how this activity ties to NGSS