4. Discussion


4.1 Analysis Of Results

As seen in our results in the table and graphs above, it is evident that the mass of the wire mesh increased significantly, from 160.6g to 188.2g, while the mass of the copper rod decreased from 90g to 70.6g. We also noticed a greenish-blue deposit forming, and the deposit increasing every day, thus these deposits then contributed to the gain in weight to the wire mesh (cathode). We have also seen in decreased in weight in the copper rod. This is because the copper rod (anode). reacted together with the water. The copper (anode) became thinner and shorter as the days past, this can be supported with its decreased in weight.


4.2 Key Findings


We found out that throughout the whole experiment, there was greenish blue colouration can be seen throughout the whole set-up. It can be seen from the water to the wire mesh (cathode) to even the copper rod (anode). These observations baffled us This is because this colouration was the similar of Copper Carbonate (CuCO3). Since we needed Calcium Carbonate (CaCO3) to form on the wire mesh (cathode) instead, we got extremely worried. This is because Calcium Carbonate (CaCO3) usually appears as in a white colouration instead of greenish blue, a colouration more towards the Copper Carbonate (CuCO3), which is present in the water body.


4.3 Explanation Of Key Findings

As stated in the previous above, the greenish blue colouration which was being seen all over the set-up was caused by Copper Carbonate (CuCO3). Worried that the deposit forming on the wire mesh (Cathode) was not Calcium Carbonate (CaCO3) but instead fully Copper Carbonate (CuCO3), we decided to test for the presence of Calcium Carbonate (CaCO3) in the water. We started to test for Calcium (Ca) using the flame test. The flame test is used to identify the presence of certain types of metal in a sample. This works because metal changes the colour of a flame when they are being heated in it. Furthermore, different types of metal would result in a different coloured flame.
The steps of carrying out a flame test are started in the following:
  1. Dip a clean flame test loop in the sample solution.
  2. Hold the flame test loop at the edge of a Bunsen burner flame.
  3. Observe the changed colour of the flame.
  4. Match the colour of the flame to the type of metal it represents.
Here are some of the different colouration with different types of metal. Some of the colours would be:
  • Pale green - Barium
  • Yellow red - Calcium
  • Green-blue - Copper
  • Red - Lithium
  • Orange - Sodium
  • Lilac - Potassium


Colouration
Type of metal
Pale green
Barium
Yellow red
Calcium
Green-blue
Copper
Red
Lithium
Orange
Sodium
Lilacc
Potassium




This video of the flame test was taken by our science teacher, Mr. Ng Guo Hui.


Fortunately, there was yellow-red flame which emerged, proving that there was some sort of Calcium (Ca) present in the deposit. However, we were not sure if there was carbonate present. Therefore, we decided to carry out a carbonate test.












As seen in this picture, there was effervescence in the test tube when the hydrochloric acid was added to the sample of the deposit. This shows that there was a reaction happening. Furthermore, there was gas produced during the process. However, due to the fact that the amount of Calcium Carbonate (CaCO3) present in the deposit was too little, thus it could not generate enough gas for a proper Carbon Dioxide (CO2) gas test with limewater.

Carbonate test is carried by using an acid to react with the carbonate to give us a product of salt+water+carbon dioxide.

Hydrochloric Acid (HCl) + Calcium Carbonate (CaCO2) ➝ Calcium Chloride (CaCl2) + Water (H2O) + Carbon Dioxide (CO2)

We used a hydrochloric acid to mix with our deposit to see what was the result. End of the day, to our delight, effervescence can be seen, and carbon dioxide was being produced. However, we saw that not 100% of our deposit dissolved in the acid and there were not enough gas to turn the limewater chalky. However, this proved that there was Calcium Carbonate (CaCO3) present on our wire mesh (cathode).

4.4 Evaluation Of Engineering Goals

Fulfilling our engineering goals, we managed to develop a self-sustaining system, which is able to trap the solar energy of the sun to create an environment suitable for coral growth. As seen in our result, we were managed to get some deposit of Calcium Carbonate (CaCO3) forming on our wire mesh (Cathode). This Calcium Carbonate (CaCO3) forming on the wire mesh, is suitable for coral growth, and we believe it would be able to combat the problem of coral depletion happening now.
 

4.5 Areas For Improvement


Some areas for improvement are:

  • Placements of the crocodile clips on the wire mesh (cathode) and the copper rod (anode)
    • Based on our observation, we inferred that the position of the crocodile clips (on the anode and cathode) directly affects the concentration of the deposit. Therefore, in future setups, we would place several crocodile clips all around the anode and cathode to ensure even concentration of deposit.


  • Water cooler
    • At the start of the setup, we stated that to ensure optimal coral growth, we need to ensure an optimal temperature using a water temperature controller. However, the temperature controller given to use was not in working condition. Therefore, we made do without it, and it still worked, but we believe that with it, the success rate will be even higher.
  • Measuring of the wire mesh (cathode) and copper rod (anode)
    • When measuring the mass of the anode and cathode, for some days we forgot to let them dry out completely. Therefore, the measurements may not be 100% accurate, but we still measured a continuous increase despite that fact.
    • Also, we were unable to measure the mass of the wire mesh and copper rod daily (due to the lab not being available to us on days without ISS lessons), therefore, the results may have a sudden spike due to a sudden increase of 6 days instead of the usual 1 day.
  • Sampling size + Dilution of  Hydrochloric acid (HCl)
    • Due to the fact that the sample that we extracted was very little, therefore we could not see much effect between the gas produced at the limewater. This is because our concentration of Calcium Carbonate (CaCO2) was too little. Therefore, we should have extracted more samples of our deposit, thus increasing the concentration of Calcium Carbonate (CaCO2)
    • Furthermore, the dilution of the Hydrochloric acid (HCl) also affects the outcome of the products. This is because the concentration of Hydrochloric acid (HCl) needs to fit with the amount of sample we have. Though unclear whether the concentration of Hydrochloric acid (HCl) needs to be increased or decreased, we believe that changing the concentration of Hydrochloric acid (HCl) might have an impact on the items being produced.

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