Reflection: Joy Endothermic Reaction Demonstration - Section 3: Demonstration


Chemical reactions by themselves can be interesting. I have found that when an element of danger is introduced the students perk up and pay close attention. At no point are any of my student EVER in any danger - they just don't know that. Ammonia stinks, but no one is going to die by inhaling ammonia fumes in the amounts generated with this demonstration.

I start out by explaining that if any of these fumes escape we will we have to evacuate the classroom and call the local fire department's hazardous material team to clean up the mess (small fib). If you really want to get their attention, tell them that once the haze mat team has arrived they will set up decontamination showers outside and clean every student involved (aka the scene from Monsters Inc when a monster has a kid's sock stuck to his fur and a Code 2319 is called). This won't happen, but they don't know that. A little fear provides a lot of student attention.

To prove that the chemical reaction indeed froze the flask to the wood, I ask for a volunteer and flip the flask upside down over their head. There are a lot of screams and gasps when I do this. It's a great deal of fun and the kids enjoy the demonstration. 

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Endothermic Reaction Demonstration

Unit 5: Chemical Reactions
Lesson 9 of 11

Objective: Students will be able to observe an endothermic reaction which mixes barium hydroxide and ammonium thiocyanate to freeze a flask to a wooden plank.

Big Idea: Endothermic reactions are cold and more difficult to demonstrate. This is safe, cheap, easy, and exciting.

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  145 minutes
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