Sari on Science: A simple at-home activity for explaining a pandemic

Explaining a pandemic to kids can be difficult, but there are several simple activities that can help us talk about germs and disease spread.


COVID-19, coronavirus, pandemic, how germs spread, how disease spreads, explaining a pandemicThank you to everyone who is staying home, social distancing and wearing a mask to protect others during this COVID-19 pandemic. We are living in a tough time, and we are in it together!

Explaining a pandemic to kids can be difficult, but there are several simple activities that can help us talk about germs and disease spread. I use glow powder on hands and objects to demonstrate this at Arizona Science Center, but here’s a version that’s easier to try at home with items from the pantry or grocery store.


  • 1-liter bottle of tonic water
  • 1-liter bottle of club soda (or any clear, carbonated liquid — lemon-lime soda works, too)
  • Clear cups (2-3 per person)
  • Spoons (1 per cup)
  • A good blacklight flashlight (the kind used to look for scorpions)


  • Fill two cups about 2/3 full with tonic water. Shine the blacklight on the tonic water, which should glow with a blue tint. These represent infected individuals.
    Fill the rest of the cups 2/3 full with the club soda. These represent healthy individuals. All cups will look similar with a clear carbonated (bubbly) liquid in them. These do not glow when illuminated by a blacklight.
  • Mix up all the cups and have all participants choose 2-3 cups at random.
    Talk about ways germs spread: Through talking, singing, sneezing, coughing and touching contaminated surfaces; represented in this activity by “interactions.”
  • Go around your group so that each person is allowed an interaction with another participant. During this interaction, each participant will pour a little liquid from their cup into the other person’s cup. Continue until each person has three turns interacting with another participant, switching between their 2-3 cups randomly (or not at all) for each interaction.
  • Check the liquid in the cups with your blacklight. What do you observe?
  • Continue so that each participant gets another five rounds of interactions with the rest of the group. Check your liquid with the blacklight. What do you notice now?

What’s happening?

Tonic water contains quinine, which fluoresces (or glows) bright blue under ultraviolet light produced by your blacklight. When sharing liquid from cup to cup, some of the tonic water is getting mixed into other cups. This is a simulation of how interactions like coughing, sneezing, talking, singing, and touching contaminated surfaces can spread germs from an infected person to a healthy person — even if there is no obvious sign of infection. (All the liquids look the same without the blacklight).

The more “interactions” in this activity, the more you will see the tonic water (blue glow) show up. By the end of this activity, almost all of your cups will glow blue, though they may glow more weakly since the tonic water is diluted. This represents how quickly a disease like COVID-19 can spread in a community.

To take this a step further, place one of your non-tonic water cups six feet away at the beginning of the activity and have no interactions with it. At the end of the activity, this may be the only cup that shows no glow, and is a good representation of how social or physical distancing can help prevent the spread of disease. For more information on COVID-19, including science videos and more activities you can try at home, visit