The Chemistry Club at Portsmouth Abbey put the wheels in motion! On Tuesday night, April 13, the club held a chem-e car race, using a chemical reaction to propel the vehicles across the ice hockey rink (the ice was removed in March).
Students broke into teams to create vehicles using legos, soda bottles, and nails. They "powered" the cars by creating a reaction between baking soda (sodium bicarbonate) and vinegar (5% acetic acid) to produce CO2 (gas), water, and sodium acetate. It was the carbon dioxide gas that propelled the reaction.
The teams competed to find the stoichiometric ratio of baking soda to vinegar that worked the best. Around 100 mL of vinegar and 7 grams of baking soda seemed to be the magic formula. In stoichiometry, this amounted to approximately 0.0833 moles of acetic acid and 0.0833 moles of sodium bicarbonate to produce 0.0833 moles of carbon dioxide gas. The mixture causes the pressure of the carbon dioxide gas in the 500 mL bottle (now about 400 mL of space for gas) to build up to a pressure of around 6.0 atm (six times atmospheric pressure), and this propels the car when the gas is released.
A nail was placed in the top of the fuel bottle and removed once the ingredients were mixed, allowing the CO2 gas to be released to propel the car. (Unfortunately, vinegar and baking soda spewed everywhere as a result). The hockey rink base provided for easy cleanup.
The students quickly found that too much weight slowed the car down. They also found that shaking their cars to mix the ingredients and waiting the ideal time for pressure buildup before releasing the nail achieved the greatest distance.
The vehicle design was also very important. Cars with wheels (axles) that turned easily were faster overall. The lighter cars generally performed better, but if the car was too light, some of the environmental hazards knocked them off track or send them into a tailspin. Other impediments included contact with a wet spot on the floor; filling the ingredients into the sealed bottle too slowly; the nail hole becoming enlarged, or gas releasing off-center.
Despite the spills and misses, all were in good spirits and loved watching the other teams' cars speed around the rink.
The winning car, built by Alex '22, Bryan '22, Dierdre '21 and Mary '24 raced over 163 feet, with the second-place car, built by Chemistry Club first-timers Caroline '22, Charlotte '22, and Sara '23, covering 158 feet! Congratulations to all of our student scientists for a terrific showing, and thank you to Chemistry Club advisor Mrs. Susan McCarthy for her guidance throughout and to Ms. Christina Fontana for helping to judge this event!
Pictured Below: The winning team Alex '22, Bryan '22, Dierdre '21 (Mary '24 not pictured)