OELP Overview

Non CID-post: Science Practical Reflection.

 

The reflection I am going to write is about the second biology practical we have had. The practical was about testing the presence of some substances by using indicators or tests. The substances we were testing for were reducing sugars, protein, fat or oil and starch. To test for reducing sugars, 2cm3 of Benedict’s solution was added to 2cm3 of glucose solution, which were then shaken well, and put into a boiling water bath. There are reducing sugars when the benedict’s solution has a brick-red precipitate. To test for proteins, we added 2cm3 of sodium hydroxide solution to 2cm3 of egg albumin solution, or also known as egg white, and shook the resulting mixture well. We then added 1% copper (ii) sulfate solution dropwise and shook well with each drop. This test is also known as the Biuret test. If there is protein present, there should be violet coloration present. To test for starch, we added 2 drops of iodine solution into 2cm3 of starch suspension. The iodine solution turns blue-black if starch is present. To test for the presence of fats/ oils, we conducted the Ethanol-emulsion test, where we added 2cm3 of ethanol to 2cm3 of oil, and shook the mixture well. After which, we added 2cm3 of water. If there was a white emulsion formed, then fat or oil is present. Water was used as a control for all four experiments, so that we could have evidence that the reaction in a solution was due to something that was not present in other substances.

  This practical was one of the most challenging practical I have done. The number of substances that are required for this practical contributed to the difficulty of the practical, as I had to remember which substance was which, as they bore similar appearances. The similarity in appearance between the substances confused me as to what test I was doing, as I was afraid of adding the wrong thing to the wrong substance. The time limit set by the teacher also added to our stress and made us pressurized, hence increasing our chance of mistakes. Handling and manipulating so many test tubes at once was a problem, hence we ended up having a higher rate of test tube breakage than our other practical lessons. Through this practical, I have learnt how to use time efficiently, example would be to boil water while setting up the experiment. This experiment allowed me to have a try at keeping a cool head under pressure. I feel that these can be useful for our future practicals.