Decontamination Algorithm


While it can be obvious when something has visible dirt on it, it’s harder to tell when something has invisible contamination that needs to be cleaned away! Sticky handprints from a PB&J sandwich, food and pet allergens, pollen and germs can all be hard to spot. Can you create a series of questions, or an algorithm, to help figure out what surfaces have been touched and contaminated? 

Design Challenge

Create a sequence of questions to help you figure out what surfaces are contaminated after you or someone else does a task. 


Computational Thinking




20+ min

(Optional) +1 hr to make colored cornstarch

Key Concepts

Critical thinking, problem solving, iteration, algorithms

Want a challenge?


Play the classic game of 20 Questions with a friend or family member. You just created an algorithm!

Want a challenge?


Create a sequence of questions to help you figure out what surfaces in your home are contaminated after someone walks through it.

Want a challenge?


Can you make your algorithm more efficient? Try asking fewer questions and see if you can get the same result.

If you think this looks fun, wait ‘til you try these!

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