A Chemical Test-Drive: Fun with Chem-E Cars

Wilson, eNotes’ Math and Science intern, shares his experiences of creating a car from scratch and racing it in a statewide contest. Science nerds, prepare to freak out!

The day finally came. After hours and hours of testing, we were finally ready to have our miniature car compete with those of 10 other California universities, including Stanford, UC Davis, UC Berkeley, and San Jose State, at the Chem-E (Chemical Engineering) Car competition hosted over the weekend at UC San Diego.

The requirements were that this car should be relatively light, be powered by a chemical reaction of our choice, be able to have a time-dependent braking mechanism, and be able to carry a certain amount of weight (water) across a certain distance in under 2 minutes.

Our “Bruin Car” ran off of an electric motor powered by a hydrogen fuel cell, which was supplied hydrogen using a chemical reaction between hydrochloric acid and magnesium. The braking mechanism was an iodine clock reaction that would interfere with the transmittance of light onto the photoresistor in our circuit; thus, when the solution turned completely dark, the photoresistor’s resistance would increase, causing the current to drop and cut off the source of electricity to our electric motor.


The length of the magnesium would be our primary determining factor of how far the Bruin Car travels, so for 4 hours a week and for 10 weeks (in addition to perfecting the iodine clock reaction) we would perform test runs on varying lengths of magnesium to acquire data for the day of the competition, as the distance that the judges would want our car to travel was unknown to us until the day of.

The trip there was very exciting; a good break from all the stress in the average college student’s life. The drive from UCLA to UC San Diego took roughly two hours, but it went by extremely quick. We were all having such a good time talking and goofing around in the van that time just flew by. (We also decided to stop by Phil’s BBQ in San Diego for a quick lunch break. If you ever get the chance, try it out! Their food is amazing!)

We arrived at the engineering schools of UCSD at around 3:00PM. The first thing we noticed was that their engineering buildings are so much nicer than ours. The engineering building at UCLA seems to be one of the older buildings on campus that needed serious reconstruction while those at UCSD appeared to be the nicest buildings on campus. We were most amazed with one particular artistic object they had known as the, “Fallen Star.” It is a small house positioned off the ledge of one of their engineering buildings. This was quite an incredible sight.

The rest of the day consisted of checking in, registering our Bruin Car, participating in the poster competition (where other engineers and students would be able to read about the design and mechanism of your car), preparing all the chemicals that were needed for the competition the next day, and playing beach football. Then we all went out for a late-night meal before checking in at a Howard Johnson hotel a few miles off of campus.

We all woke up the next morning after 4 hours of sleep to try out the dining hall food of UCSD and see how it compared with those of our own. Although the variety was definitely different and provided a fresh perspective, the taste exceeds that at UCLA’s dining halls.

Judgment day was finally here. The judges had decided to hold the competition right outside one of the engineering buildings, where there was a pretty steep, downward slope. The finish line was 50 feet away from the starting point. To test both the acceleration and deceleration of the car, we would have to try to get the car to stop as close to the finish line as possible in the shortest amount of time.

Another example of a Chem-E car, from the University of Florida

Due to the limited space and the amount of competitors there were, the schools were divided into groups of three. When it started, the cheers from each school, in support of their car, were deafening. Out of the first group that went, only Cal Poly Pamona did very well. They were within 3 feet of the finish line, while the others had trouble just getting started or managing to stop at the finish line. The next group went with the same success rate as the first; only one car was able to successfully get close to the finish line.

Finally, our group was up. The UCLA 8-clap cheer rang out. A 25cm-strand magnesium was dropped into the hydrochloric acid. The circuit was turned on and………… our car blew 10 feet past the finish line. We had no idea that the slope had that much effect on our momentum. It also didn’t help that our wheels lacked sufficient traction. Fortunately, each car is allowed two attempts. Unfortunately though, we had no data on how far a strand of magnesium shorter than 20cm would take us, and we definitely needed something shorter if we wanted the car to stop near the finish line. We were basically shooting in the dark after that. We decided to try 18cm. The magnesium was dropped. The 8-clap began again. We all crossed our fingers and watched as the car strolled about 8 feet past the finish line.

Unfortunately, we didn’t place. Cal Poly Pamona got 1st. San Jose State got 2nd. UC Berkeley got 3rd.

Although we were all a tad disappointed, overall this was a very good and fun experience. We got to see the beautiful engineering buildings at UCSD. We got to try the delicious food at Phil’s BBQ. We networked with the students at other schools. We bonded with one another in the van and at the beach. It was definitely a weekend well spent. Now, we are back in the lab, preparing for next year because this time, we will be much better prepared. We will be claiming first. Let’s go Bruins!