REFLECTION
Lab 2
In this lab, we were doing titration techniques. For this lab, there are many precautions
should be taken. In this lab, I had make a mistake which is overshooting the endpoint of the
analyte. I realized that with a little mistake, it will cause error to our result. So most
importantly, take care not to overshoot the endpoint as the presence of large excess of titrant
will cause the resulting error. There are many others precautions that we should take. For
example, we must make sure that we used very clean glassware to avoid other substance mix
with our analyte or titrant. To deliver an accurate volume of solution, we must use pipette
rather than measuring cylinder. Besides, it is best to titrate into Erlenmeyer flask because we
can swirl it easily without danger of sloshing out the content. When doing this experiment, I
realized that we should work carefully and meticulously.
Lab 3
In this lab, we were using a spectrophotometer to measure the protein absorbance. For
this lab, there are many important things that we should know and apply. Firstly, we need to
measure the volume of all solution ( gelatin, H2O, biuret ) accurately. I did not transfered the
solution slowly into the cuvette, so the spectrophotometer cannot read the absorbance
accurately. So, we had to repeat the step again. The most important when doing this
experiment is to set the absorbance to zero and it will serve as a blank solution. Why ?
because we want to measure how much light is absorbed by protein alone. From this
experiment, I got to learn something new which is how to use the spectrophotometer properly
and learn about it uses.
Lab 4
In this lab, we need to extract and detect the presence of lipid in various sample of
foods. There are also some precaution that we should noted in this experiment. First of all, we
want to get the lipids to dissolve in the petroleum ether. We must make sure that the lipid is
dissolve completely. After that, we decant the petroleum ether to get the solid portion and
liquid portion. Next, we need to evaporate the petroleum ether. For this step, we must use hot
plate or allow the beaker to dry overnight but it will consume much time, so using a hot plate
or water bath is more efficient. Most importantly, we were reminded to not attempt to
evaporate the petroleum ether with a flame. As we know, ether is teribbly dangerous because
it is flammable and explosion hazard. From this experiment, I realized the importance and the
effects of content of lipid in our diet.
Lab 5
When doing a microbiological laboratory, there are many aspects that we need to pay
attentions. For example, in this lab, we need to produce isolated colonies on agar plate using
streak plate method and determined the effect of handwashing using various step. . For this
part, it is crucial to maintain a sterile work area surrounding us to make sure that the bacteria
do not affect our health and the people surrounding us. Unfortunately, when doing the streak
plate method, I forgot to sterile the loop with 70% ethanol. Next, we are required to do gram
staining to differentiate between the 2 major categories of bacteria which is gram positive and
gram negative. For this part, there is no problem as we had followed the step properly without
leaving even one step behind.
Lab 6
In this lab, we were used paper chromatography to separate plant pigments from a
plant using a hydrophobic solvent and is called chromatography techniques. In this lab, I had
to repeat the step over and over again because the leaf extract got dissolve in the solvent.
There are many step that we should follow properly. Firstly, the paper must be placed
vertically and straight into the test tube to prevent our mobile phase get bent. Moreover, we
must ensure that the leaf extract is above the solvent all the times. If it submerged in the
solvent, the extract would dissolve into the solvent and prevent them to separate. Most
importantly, we need to mark the solvent level when we removed it so the point at which the
solvent stopped could be noted in case the solvent kept advancing.
