An exciting 35-minute 5th grade hands-on science lab investigating chemical reactions, carbon dioxide gas pressure, and launch times using Alka-Seltzer tablets, water, and snap-top film canisters.
“The rocket launched with carbon dioxide gas. Where were the Carbon and Oxygen atoms before we added water? Were they already in the room, or locked inside the tablet?”
Prompt 2: Why Did Crushed Powder Fire Faster?
“Look at your stopwatches. Why did Trial B launch so fast? What did crushing do to the surface area? How did that help the elements collide faster?”
5th Grade Misconception Busters
Student Misconception
Scientific Reality & Reframing
“Brand-new elements were created out of nothing to make the gas.”
Atoms cannot be created or destroyed! The Carbon (\(\text{C}\)) and Oxygen (\(\text{O}\)) were already in the tablet molecules and rearranged into \(\text{CO}_2\).
“An explosion happened inside that created hot fire.”
Zero fire or heat! It is an endothermic reaction that actually absorbs heat and gets colder, generating mechanical gas pressure.
“Crushing the tablet gave it more chemical elements.”
The number of atoms is identical. Crushing exposes greater surface area so water dissolves the crystals faster, speeding up atomic collisions.
Exemplar Student Response Key (CER)
Claim: YES, a chemical reaction powered the film canister pop rocket.
Evidence: 1. Vigorous bubbling generated high gas pressure that popped the sealed lid and propelled the canister upward. 2. The canister body felt noticeably cold to the touch immediately after launch (endothermic cooling).
Reasoning: Water dissolved the tablet, allowing atoms of Sodium (\(\text{Na}\)), Hydrogen (\(\text{H}\)), Carbon (\(\text{C}\)), and Oxygen (\(\text{O}\)) to rearrange. Carbon and Oxygen combined to produce carbon dioxide gas (\(\text{CO}_2\)). Because gas takes up far more volume, pressure built up inside the rigid canister until the lid snapped open, providing thrust. Crushing the tablet increased surface area, speeding up the reaction.
Fast Finishers: Test water temperature! Does warm water make the elements react even faster?
ELL Sentence Starter:“The elements Carbon and Oxygen made... gas that pushed the rocket...”
Pop Rocket Facilitator Guide • Section 2 Page 2 of 2
