Lab Conclusion 6v2m5s

WHAT’S GOING ON HERE? LAB CONCLUSION

1

In the lab, “What’s going on here?” six substances were tested for appearance, solubility in water, conductivity of solutions, and relative melting points. These substances were lauric acid, sodium chloride, sucrose, stearic acid, potassium bromide, and starch. Upon testing each of these substances, there were clear trends that were instantly recognizable. There was high conductivity as a solution in sodium chloride and potassium bromide, while there was low conductivity as a solution in the rest of the compounds. All the compounds were soluble except for lauric acid and stearic acid. The compounds with melting points higher than 800 degrees Celsius were sodium chloride and potassium bromide. The compounds with melting points lower than 800 degrees Celsius were lauric acid and stearic acid. Finally, the compounds that burned when heated were sucrose and starch. Based on this data, the substances were then categorized into 3 groups. The first group consisted of the acids, lauric acid and stearic acid. The second group consisted of the ionic compounds, sodium chloride and potassium bromide. The last group included sucrose and starch. Conductivity was high in sodium chloride and potassium bromide because they were ionic compounds. Ionic compounds are not very conductive as solids but when dissolved in water, they can conduct electricity very well. This is because when ionic compounds are placed in water, the bond between the ionic compounds breaks. Now, there are just two separate kinds of ions that are not bonded in any way. These ions can now a current between each other making them conductive. On the other hand, the rest of the compounds do not form ions. Therefore, they are poor conductors as a solution. Sodium chloride and potassium bromide were soluble because they were polar. Polar compounds have more electrons present on one side of their molecule than the other side. This causes each molecule to have a positive and a negative side. Because water is also polar, it “pulls” on the molecules of a polar compound and if it pulls hard enough, it can break apart a molecule, dissolving it in water. The rest of the compounds were not polar. Because of this, the water could not pull the molecules apart and dissolve them. Finally, the melting point of the ionic compounds was greater than 800 degrees Celsius because they formed ionic bonds. Bonds in an ionic compound are stronger than bonds in a covalent compound. Because of this, it takes more energy, in this case heat, to force the ions further apart. Since covalent compounds have weaker bonds, it takes less energy, heat, to force the ions apart. This is why lauric acid and stearic acid started to melt quickly. Sucrose and starch burned because they have more complex structures. When sucrose and starch are heated quickly, they will combust and burn because of their complex structures. While conducting this lab, the sucrose did not burn as it should have. The observation that was made was that the sucrose had a melting point less than 800 degrees Celsius. This did fit any trends that had been showing up. A reason for this may have been cross contamination. The scoop may not have been wiped between the placements of each compound on the tin plate. This may have caused another compound to be placed on the tin plate instead of the sucrose. Because of this, the incorrect substance was observed and noted as sucrose. This would look as though sucrose melted when in reality, there was a different substance on the tin plate.