BEAM: Soda Mentos Reaction Lesson Siddarth Krishna Week of 3/11/13 - 3/15/13

Overview & Goals Use scientific reasoning to figure out what properties of the soda, mentos, and gas released cause the mentos-soda reaction to happen Have fun playing with soda and mentos Throughout the lesson: don’t give away answers! Let the kids guess and reason

Agenda Introduction: What is soda? Investigating the Gas: Mentos-Soda Demo Investigating the Soda: What works and why Investigating the Mentos: Surface properties

Introduction After asking what they think soda is made up of, tell them it’s mainly water, sugar, and fizz. Talk about what they think fizz is. Then do the mentos-soda balloon demo as a group, looking at properties of the gas released Then, break into groups for the experimentation (Mentos, Soda) modules while mentors facilitate

Module 1: Gas Investigation For the kids to determine what is released by the reaction Demo: (outside, in a group): Blow up a balloon using mentos Put ONE mento into balloon (all the way in) Fix balloon’s mouth over soda bottle’s lip -Then push the mento into the balloon. Hold balloon vertical, with a hand on the lip of the bottle! Liquid will shoot into balloon. Let it drain, then carefully take balloon off and tie it off Might take two tries…

Module 1: Gas Investigation (ct’d) -Ask the kids what they think happened! Don’t just tell them it was CO2 gas released. Some might already know it’s CO2, but ask them how they could prove it Blow up another balloon to the same size with air. Ask kids if they think the CO2-balloon is the same as the air balloon. Then show them how the CO2 balloon falls faster, and ask them why they think that happened Main point: the gas released by the rxn is not air, it’s something else. (At the end, we’ll tell them it was CO2)

Module 2: Soda Investigation Divide students into 2-3 groups Give them the individual ingredients of soda(club soda, sugar water, soda), let them experiment Goal is to figure out what property of the soda causes the reaction (fizz, not sugar) Pour liquids for them (~150 mL in cups) Help them make an experimental plan and interpret their results, but don’t give away answers Encourage them to be creative! They can try multiple mentos, water-soda mixtures, etc

Module 2: Soda Investigation (ct’d) They can write down observations, conclusions, etc on paper Note: Sugar into soda causes the reaction too – but students shouldn’t conclude it’s just the sugar that causes it Also: After mentos rxn is over, the soda will be flat and won’t do the rxn again. The kids should notice this Also: The reaction works better with diet (the sugar sweetener is involved), but we are ignoring that effect by not using diet

Module 3: Mentos Investigation Looking at what property of mentos causes reaction to happen I made “smooth” mentos by microwaving them in water and then letting them dry. They won’t work in the reaction. The kids will see that these don’t work, and can use magnifying glasses to see the smooth vs rough surfaces Answer: Rough mentos surface are nucleation sites for CO2 bubbles to form and then escape Let them figure out on their own! It’s the surface, not some chemical in the mentos, that causes the rxn.

Conclusion Briefly discuss with students what they learned- what they think is going on in the mentos-soda reaction and why. Their pieces of paper should come handy. Tell them the answer: The rough mentos surface helps the CO2 (fizz) in the soda form bubbles and escape as a gas!

Reminder: Materials ~20 Cups (for kids to experiment in) 3 Packets of regular mentos ~4 Balloons, two 710 mL Soda bottles (Gas Investigation) Two 2L Soda bottles, 1L sugarless Club Soda, plain sugar (Soda Investigation) Magnifying Glass + 1 packet of Microwaved mentos (for Mentos Investigation)