Using Chemical Mysteries (in the IB) Chemistry Classroom

Balloon in a Bottle

Inspired by Tom Kuntzleman*, I started using mysteries in my chemistry curriculum this past year. The first mystery I shared with my students was . While my magician skills aren't perfect, I was able to get the students asking questions and proposing hypotheses. For my IB students, it really allowed me to delve into a number of topics (e.g. combustion, intermolecular forces, polarity, density). And thus an idea was born: Using one mystery per topic. Since I teach mostly IB Chemistry, I've got 11 main topics and my work has begun to find and/or develop a mystery for each unit. It's very early in the process, but here's what I have so far:





Main Connection To Curriculum


1: Stoichiometric Relationships


Balloon in a Bottle (discussed below)


Gas Laws


2: Atomic Structure




3: Periodicity




4: Chemical Bonding and Structure


(from Tom Kuntlzeman)


Intermolecular Forces


5: Energetics/Thermochemistry




6: Chemical Kinetics


Clock Reaction


Effect of Concentration on Rate of Reaction


7: Equilibrium




8: Acids and Bases


(from Tom Kuntlzeman)


Acids and Indicators


9: Redox Processes


Potato Clock


Voltaic Cells


10: Organic Chemistry




11: Measurement and Data Processing (includes spectroscopy)





In March, I saw this tweet: 



So I made my own to show some students:


Given my project of finding a mystery for each unit, I chose this mystery for Topic 1, as it includes gas laws. So I tried the demo with my Intro Chem class. I showed them the balloon and challenged them to make a replica. They were given a similar Erlenmeyer Flask and a balloon. They could handle my example, but not take it apart. The first attempt at recreating the balloon often involved putting the balloon into the flask and trying to blow it up. When this didn't work, they started asking questions and trying other things - such as putting a straw in to allow air in the flask to leave as the balloon filled the flask when it was inflated. The students got close with this general method, but could never pull off an exact replica of my balloon. Then a group got a hot plate and started heating some water in the flask, as it was obvious that there was some water inside the flask of my example. They then put the balloon on top and watched in horror as the balloon expanded more as the water heated. It took a few more rounds of trial and error before a group figured out the real method: heat a small amount of water to boiling on a hot plate, then carefully place a balloon over the top. As the water condenses, the pressure inside will decrease to the point where ambient pressure outside the balloon will push the balloon into the flask.

One of my summer tasks is to find mysteries for the other units. And so it begins!

Do you have any mysteries you've used? I'd love to hear from you. And I'll keep you posted as I develop and/or modify mysteries for the other units.


*Tom Kuntzleman's Mysteries here: 

Mystery 1:

Mystery 2:

Mystery 3:

Mystery 4:

Mystery 5:

Mystery 6:

Join the conversation.

Comments 3

Tom Kuntzleman's picture
Tom Kuntzleman | Sat, 06/25/2016 - 13:19

I like what you did with this mystery: You showed the end product of an experiment, but hid the procedure. Then you challenged your students to mimic the hidden process. What a cool idea! I look forward to seeing what other types of mysteries you develop.

Pascual Lahuerta's picture
Pascual Lahuerta | Sun, 10/23/2016 - 02:50

I send an experiment that I have used to describe the scientific method but might serve as a new mystery. You will say.

Students see two glasses full of "water". In each glass an ice block of similar size is placed and left unstirred while the ice melts. Surprisingly one of the ice melts faster than the other. They should find out why. The reason is that one of the vessels contains a concentrated salt solution. 

You can take advantage of the experiment asking the students to repeat it.  They should find out why that different behavior is produced. The origin is in the different density of the liquid in both vessels. 

I hope you enjoy as much as I did, readding the explanations of the students.

Pascual Lahuerta

Lowell Thomson's picture
Lowell Thomson | Tue, 10/25/2016 - 19:32

Hi Pascual,

Thank you for sharing that idea. It is fantastic! Colligative properties related to freezing point depression of mixtures doesn't happen to be in the IB curriculum currently, but there are plenty of benefits from this type of exploration regardless of the actual "curriculum" being taught.

I like the idea and will be looking for a good place to insert it into my class.

Thank you for sharing the idea.