Skip to main content

Witness a chemical reaction with this hands-on experiment

Let’s Talk Science and the Royal Society of Canada have partnered to provide Globe and Mail readers with relevant coverage about issues that affect us all – from education to the impact of leading-edge scientific discoveries. Let’s Talk Science offers a number of fun activities to get youth engaged in STEM.

Get your popcorn kernels dancing with this uplifting chemical reaction.

What You Need

● Baking Soda (1 tsp)

● Vinegar (1/4 cup)

● Water (1 cup)

● Un-popped popcorn kernels

● Measuring cup

● Shallow pan

● Tall glass or jar

● Teaspoon

What to Do

  • Place the glass in the centre of the shallow pan and add several popcorn kernels into the glass.
  • Predict what will happen when each of the following steps occurs:
  • 250 mL (1 cup) of water is poured into the glass.
  • 60 mL (1/4 cup) of vinegar is poured into the glass containing water.
  • 5 mL (1 tsp) of baking soda is added to the vinegar/water solution (without mixing)
  • Pour 250 mL (1 cup) of water into the glass and observe what happens.
  • Add 60 mL (1/4 cup) of vinegar into the water in the glass and observe what happens.
  • Add 5 mL (1 tsp) of baking soda to the vinegar solution (do not mix!) and observe what happens. Is this what you expected to happen? Why or why not?

What’s happening?

When the vinegar and baking soda are combined, a chemical reaction occurs between the acetic acid in vinegar and the sodium bicarbonate in baking soda. This causes a release of chemical energy and the formation of a gas (carbon dioxide).

Some gas bubbles that form will adhere (stick) to the outside of the popcorn kernels and raise them to the surface of the liquid. This is because the kernels and bubbles together have a lower density than water and thus rise to the surface of the liquid. At the surface, the gas bubbles burst, releasing the carbon dioxide into the air. Once the bubbles have burst, the density of the kernel is once again greater than that of water and the kernel sinks to the bottom of the glass.

Why does it matter?

Acid-Base reactions are often used in baking to make bubbles form in cakes or cookies as they are baking. This helps make baked goods light and spongy, rather than heavy and dense.

Investigate further

● Try this experiment with objects such as rice, dried kidney beans or paper clips instead of popcorn.

● Replace the baking soda with salt or sugar and see if you get the same effect.

For more information on this topic check out these Let’s Talk Science resources:

Why do raisins dance in soda pop? (Hands-on Activities) - Let them bop ‘til they drop! What causes these raisins to reach new heights in this hands-on activity?

How can I engineer a raft so that it holds the most weight? (Hands-on Activities) - Explore the forces of gravity and buoyancy while designing a raft to hold the most weight possible.

Discover more free, English and French, Let’s Talk Science hands-on STEM activities, resources and events online.