Step 1: The Proyect

Summary of the project:
With the objective of creating a car that does not need an external source of electric energy, we searched for a way in which we could propel a small version of a car with a chemical reaction. For achieving this, we outlined the pieces we needed basing ourselves in miniatures of racing cars. Next, we sent the pieces to be cut by laser and we put them together. With all of this, we had a vehicle to test our fuel.

Our fuel had as base ingredients potassium nitrate and glucose. For preparing it in the bioengineering lab, we mixed our ingredients in the presence of heat. We prepared two mixes with the following proportions: 100g of potassium nitrate, 80g of sugar and 20 ml of liquid. The first mix used water as a liquid, while the second one used coke. Our hypothesis was that the concentration of sugar in coke would make our fuel more efficient. However, all the chemicals that it has caused the opposite reaction, preventing the redox reaction between the nitrate and sugar to happen. On the other hand, the fuel prepared with only water generated a strong reaction. Yet, it did not manage to push the car.

Step 2: Theory

Theory:
Potassium nitrate: (KNO3) Ionic salt of potassium ions (K+) and nitrate ions (NO3−), as a result, it can be classified as an alkali metal nitrate. It is often used as fertilizer, food preservative, tree stump removal and fireworks. (DrugBank, 2017) It is found in the nature as a white crystalline solid. It is water soluble, non combustible by itself, may explode if exposed to too much heat and produce toxic nitrogen oxides when exposed to fire. It is a strong oxidizing agent. (CAMEO Chemicals, 2007)

Sugar:Usually refers to all carbohydrates of the general formula Cn(H2O)n. The most common sugar is sucrose, which is represented by the formula C12H22O11. (Clarke & Singh, 2018) It’s empirical formula would be CH2O Redox reaction:An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species, were one of the reagents increases its oxidation state while the other one decreases. (Chemistry libretexts) In the case of this experiment, we will do a redox reaction between potassium nitrate and sacarose.

For this, we will consider how potassium nitrate reacts to form potassium nitrite and molecular oxygen:

2 KNO3 (s) → 2 KNO2 (s) + O2 (g)

While the reaction of sucrose (empirical) with oxygen is:

CH2O (s) + O2 (g) → CO2 (g) + H2O(g) In this redox reaction, potassium nitrate acts as an oxygen provider, being the oxidizing agent: 2 KNO3 (s) + CH2O (s) → 2 KNO2 (s) + CO2 (g) + H2O (g)

Step 3: Materials for the Car

Materials:
Structure of the car: Acrylic plate (37.5x13x0.35 cm) Four wheels of triplay (1 cm of thickness) Two wheels of triplay (0.7 cm of thickness Two iron sticks (15 cm) Solder machine Tin for soldering Laser cutter Rubber band de 40 cm

Fuel: Potassium Nitrate (KNO3) (100g) Sugar (80g) Water (20ml) Coke (20ml) Weighing scale Refractory beaker (500 ml) Thermometer Cronometer Spatula

Testing: Wick Two bottle caps Alcohol matches Cronometer

Procedure:

Car Structure: Before preparing the fuel, we built the car we were going to test it in. For doing this, we sketched the parts we were going to the need for our car in the following way (Image 1):

Step 4: Preparation of the Fuel

Preparation of the fuel:
First place the beaker on the stove, weight all the ingredients, and pour them into the container. Then, we turned the stove on and stared mixing the ingredients. Control the heat in order the water to boil (water boils at 100 °C) but stir in order the caramel not to burn.

Keep stirring for approximately 20 minutes, until the mixtures starts to solidify. The mixture will be changing colors from cream to brown (Image 4) and will start to smell caramel-like. When the mixture is between jelly and plasticine-like, it is ready to be poured into a heat- resistance surface. Carefully, knead it until it becomes totally like plasticine and shape it the way you need. Repeat this procedure with the coke sample.

In our case, we decided to prove our fuel at different scales. First, we moved to an open space and ignited an small sample (about a centimeter large) in order to prove the fuel was working. Then, we decided to test it with a little bigger mass (Image 5). We used as a container a bottle cap and filled it with fuel. Before the fuel is completely solidified, make sure to insert the wick. We sprayed the wick with alcohol and then setted it on fire.

To this point in time, we have obtained some results, so we already knew one of the fuels was not working. Reason why, we only tested the basic fuel in the biggest scale. For this, we poured the mixture inside the container of the car labeled in the sketch in Image 1 and shown as a picture in Image 3. We followed the same procedure, we inserted the wick before the mass solidified and let it harden. Then we sprayed it with alcohol and ignited it.

Step 5: Results

Obtained Results:
The mass that contained coke did not ignite The fire created by igniting the fuel was very strong, with a height of 10 cm and a duration of 3 minutes. The car did not managed to move, however the bottle tap did moved.

Analysis of the results:

At first, we thought that since replacing the liquid (water) with coke would increase the concentration of sugar, the fuel would be more effective. However, coke has a lot of chemicals in its composition that could prevent the redox reaction shown before of happening. Some of the ones that could have interfered are phosphoric acid, 4-metilimidazol, E-150, aspartame, cyclamate and potassium acesulfame ("Componentes Químicos de la Coca Cola", 2018). However, we can’t be certain about which of this was the one, since it would require a tests that test each of them separately. Although, this could be a future investigation to be done.

We managed to satisfy the objective of creating a strong fuel, even though we did not satisfy our main objective of moving the car. Even though the reaction was powerful, it did not achieved to break the inertia of the car. However, when propeling the car manually and breaking the inertia yourself, it did managed to keep the car moving.

And even though our idea of replacing the liquid that is necessary with coke did not worked out. This experiment can be tried with another liquid with great concentrations of sucrose that does not contain the chemicals in coke.

Step 6: Conclusion

Conclusion:
Finally, we can conclude that this experiment came to partially meet the objectives set by the group. We were able to compare the two types of fuel and find the concentration index of sugar or glucose in each of these. Also, we were able to test the theory behind this experiment.

Unfortunately, the main objective could not be met, which was to move the car through a chemical reaction or, in this case, with the two types of fuel that we had prepared. Nor could we obtain favorable results that show the Time, the amount of fuel used and the distance traveled by the chemical car.

Step 7: Bibliography

United States government. (2007). Chemical Datasheet: POTASSIUM NITRATE. https://cameochemicals.noaa.gov/chemical/1370
Potassium nitrate. (2017). In Drug Bank.https://www.drugbank.ca/drugs/DB11090 Clarke, M., & Singh, R. (2018). Sugar: Chemical Compound. In Encyclopedia Britannica.https://www.britannica.com/science/sugar-chemical-compound Oxidation-Reduction Reactions. Chemistry LibreTexts. Retrieved 22 February 2018, from https://chem.libretexts.org/Core/Analytical_Chemi... Componentes Químicos de la Coca Cola. (2018). iQuimicas. Retrieved from https://chem.libretexts.org/Core/Analytical_Chemi...