What's Going On?

Top of the pops

15 mins
Ages 7 – 9
Topics: Materials, States of matter

Help your class observe what puts the ‘pop’ in popcorn with this video of some explosive kernels!

Run the activity in 4 steps


This video shows a favourite snack being created. Check out our handy background information if you'd like to know more before you start.

Explain to your class that you're going to watch a short video. The aim isn't to find right answers, it's to explore ideas and find out what they know.


Before you press play, can the class guess what will happen in the video based on the image? Ask them to pay very close attention and play the video. What did they see? What do they think is happening?


Lead a discussion with your class based on the video:

  • What do they know is going on?
  • What can they see changing?
  • Why does it change
  • Can they observe any details to give them clues as to what is happening?
  • Is there something they don't know?


Extend the discussion by asking the class to describe what they saw using only one word. How many words can they come up with?

Background science

There are four types of popcorn and only one type has a thin enough husk, or outer shell, to pop. Each popcorn kernel contains a small amount of water stored in the centre.

To make popcorn pop, you need to heat the kernel to boiling point so that the water inside turns to steam, which builds pressure inside the kernel until it bursts through the husk. The heat also changes the structure of the kernel so that it's light and puffy. A single kernel of corn can swell to 40-50 times its original size! 

Take it further

Keep exploring the world of reactions and expanding gases with this Balloon Surprise activity. Or if you have the right equipment and access to a microwave, make some popcorn!