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Upper El (Mr. D): Rockets & Sir Newton


Let's make some Bottle Rockets! This is one of my favorite builds with UE. The building part is actually pretty simple, but the science behind it and figuring out a few other details is where our "challenge" comes in.


So, where do we begin with building a rocket? We revisit some of our chemistry. This is something like how our conversation went on Monday...

What were some of the products we've seen from our chemical reactions?

Heat! Cold! Light. Expanding Gasses!

It's those expanding gasses that we want. We revisited how we use combustion to power cars, cook ourselves something on the grill, and much more. The reaction we are going to use is not going to be combustion, but it still leads to expanding gasses.

Baking Soda and Vinegar come together, and one of the products of their reaction is the release of gas. But how can we use this to power a rocket?

Let's take a look at a balloon.

We blow it up, and then we let go. What happens? It flies! Albeit not straight. Still, it moves. But why? No one would guess otherwise, but why does the air flowing out of the balloon cause it to move in the opposite direction? This brings us back around to Sir Isaac Newton. This time, to his third law of motion.

For every action force, there is an equal and opposite reaction force.

It's volunteer time!

Graydon sat in one of our "wheely" chairs, and I asked him to give me a push. I rocked back a bit, and Graydon rolled away from me, demonstrating Newton's Third Law in a different way. Graydon's action force against me was met with an equal and opposite reaction force. Since he was on wheels, he rolled away while the friction of my feet on the floor kept me standing still.

I followed this up with a spectacular bottle rocket drawing... (ok, it was a decent bottle rocket drawing).


Now we know how it works. Air comes out very fast, creating an action force. The bottle then experiences a reaction force equal and opposite, causing it to fly away into the sky!

Our first problem is reached. How much Baking Soda and Vinegar do we use? What is the right ratio? Students were broken up into groups to try and design an experiment that could help us figure this out. How can we discover the best ratio? If we have a ton of Baking Soda and only a little bit of Vinegar, we'll get some expanding gasses, but not a whole lot.

After the groups discussed with a little guidance by me, we found the right idea. With any experiment, we want to change only one thing. So, we need to start with a certain amount of Baking Soda (or vinegar) and then add increments of vinegar until the reaction stops (until the fizzing ends).

That's exactly what we did on Tuesday. Students ran the experiment, and we had five groups. Another principle of experimentation is that the more results we have, the better! Two of our groups made slight errors in reading the numbers, so their results were a little off, which is why we run multiple experiments.

However, the other three groups were all within 1 ml of vinegar of each other's results! Impressive accuracy.

Finally, we used our results to calculate the ratio. For every 1 part of Baking Soda, we need 25 parts vinegar!


Thursday was dedicated to our final few problems to begin thinking about. We need to engineer a way for our rockets to be able to stand up on their own. Also, we need a way to deliver the reactants into the bottle to get the reaction started.

When we come back from break, we'll build our rockets and see how high we can get them to launch!


Happy Spring Break, everyone!

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