Wednesday, February 22, 2017

End Of School Year 2016

This year has been great for me as a science student. Being involved in many tasks in the lab has been a great contribution to my further understanding of science than just in the classroom. My favorite task this year is dissecting shrimps and squids. It was interesting and helpful for understanding anatomies of both animals. I never get to dissect animals both in my old school and at PHS despite the curriculum until this year and I look forward to doing more tasks like this next year as well.


Tuesday, February 21, 2017

[Lab] Leaf Test For Starch

Objective: To test for starch in leaves before and after

Groups: Guy, Shaq, Richy, Ghun

Apparatus
  • 4 green leaves
  • Beaker
  • Bunsen Burner
  • Tripod
  • Test Tube
  • Ethanol
  • Iodine
  • Pipette
  • White paper


Procedure
  1. After 4 green leaves were collected, 2 of them were put into the beaker of 150 mL of water boiling over the bunsen burner and tripod.
  2. After 2 minutes, the leaves were taken out from the beaker and were put into the test tube of ethanol. The test tube was then put in the warm beaker used in step 1.
  3. After some time, the leaves were taken out from the ethanol test tube. They were then laid down on a white paper along with 2 other fresh leaves.
  4. Iodine was dropped onto each of the leaves on the paper using the pipette. The color change of the iodine drops on the leaves and the soaked iodine on the paper were then observed.


Photos






Observation
  • The color of the iodine on all 4 leaves were too dark to be observed.
  • The paper soaked by iodine of the fresh leaves were colored orange — the original color of iodine. This means that the result of iodine test on the fresh leaves was negative.
  • The paper soaked by iodine of the boiled leaves were colored dark-purple. This means that the result of iodine test on the boiled leaves was positive.


Discussion Questions
  1. Why do we boil the leaves? - When the leaves are boiled, the cell walls are weakened and broken, allowing the organelles including the chloroplast out, stopping all the reactions from taking place inside the leaves.
  2. What is the leaf texture like after boiling? - The leaf becomes softer, smoother, and appear less green.
  3. Why do we use ethanol on the lead after boiling? - We use ethanol on the leaf to extract the chlorophyll out.
  4. What is the color of the water after boiling the leaf? Why? Why did some people get pink brown water? - The color of the water appeared pink brown after boiling because the leaves are relatively small and thin relative to the leaves of other groups. The boiling time is therefore too long for the leaves and substances other than chlorophyll are extracted as well.
  5. When you test for starch with the iodine, why did the paper turn black? - After the iodine is dropped onto the boiled leaves, the iodine turned black because the starch test is positive. When the iodine soaks the white paper, it then turned the paper black.
  6. What happened to the iodine test on the unboiled leaf? Why? - The iodine didn't turn black for the unboiled leaves because the chlorophyll and the starch is not extracted out of the cell.

Wednesday, February 1, 2017

[LAB] Titration

Objective: To learn how to use the data from Titration to calculate the concentration of an unknown acid/base.

Group: Guy, Shaq

Apparatus

  • Strong Acid (HCl) + Phenolphthalein
  • Weak Acid (HCl) + Phenolphthalein
  • Base (NaOH)
  • Stand
  • Clamp
  • Burette
  • Beaker
  • Filter Funnel
Procedure
  1.  The Burette is clamped onto the stand. Then, the base is poured until it reaches 50mL mark of the burette.
  2. A beaker filled with 10mL of acid is set up under the Burette stand.
  3. Carefully and patiently, the base is released from the burette. Every time the base is released and the indicator turns purple, the beaker is swirled. Until the acid permanently turns purple, more drops of the base are added to the acid.
  4. Once the acid does not turn clear again even after swirling, the volume of added base was identitied by looking at the scale on the Burette.

Photos


Data

Questions
  1. What is the molarity of the HCl? - 0.365M
  2. What is the molarity of COOH — acetic acid? - 1.285M
  3. What are sources of errors in the experiment? - Because the change is very critical, a single drop can make the difference. The result can be inaccurate if multiple drops of base is released at a time and the acid does not revert back
  4. Conclusion: Titration can be used to calculate the concentration of an unknown acid/base solution based on another solution of opposite pH with known concentration. However, the result can be inaccurate if you are not very careful and patient in the process.

Monday, January 16, 2017

[ESSAY] Why Thailand should not allow GMOs


Although GM plants have a number of benefits, it is too underdeveloped to be allowed publically in Thailand. First of all, it is difficult for the laws to control and prevent selling of GM products with not enough testing in the market. The risk of big damage from the GM plants is too great for the benefits it provides. Next, GM plants contain antibiotics, which will weaken the effectiveness of antibiotics used in your body when actually needed. Finally, it is impossible to prevent contamination of GM pollen into natural crops, meaning that GMOs will also alter the genes of natural plants instead of only within the GM plants. These make it more wise for Thai government to not allow GMOs given the current stage of the technology.

Sunday, January 15, 2017

[LAB] Plant Grafting

Objective: To learn about grafting plants.

Group: Guy, Shaq, Ohm, Richy


Hypothesis: If the cut maintains the connection, then the petiole should join with the node.

Apparatus
  • Plant
  • Scalpel
  • Lab Scissors
  • Clay
  • String

Procedure
  1. The chosen scalpel is cut in V-shape at the node.
  2. The leaf of the same specie is cut in V-shape at the petiole.
  3. The cut of the leaf is held onto the node so that the gap is in an interlocking position.
  4. The graft gap is sealed by clay and tied over with string.
  5. The graft is left for 4 days before it is observed again.

Photos



Question
  1. Why do we use clay? - We use clay to seal the gap in the graft. If the gap is not sealed, the cut would be exposed to the outside air and the water and nutrients from the node will not be able to reach the petiole side of the cut.
  2. Why do we cut at the node? What is the node? - A node is the region on the plant stem where branches can be grown out from. We cut at the node because the node is where the vascular bundle is available to sustain new grafted branch.
  3. Why do we use string to tie it? - We use string to tie over the clay because the clay can be viscous over a long time. Without string to tie over, the weight of the leaf will degenerate the original shape of the clay, causing the grafting gap loss its interlocking position.

Photos (4 days later)


Observation (4 days later)
  • The grafted leaf along with its clay and string fell off to the ground.
  • We suspect that the rainy days are responsible for the fall
  • The leaf, however, is still alive. Which we hypothesize that the clay holds the water from the rain and cover up the opening in the petiole, keeping the leaf alive.

Discussions
  • KK's plant graft worked because the clay holds their plant in the right interlocking position, while others' plant graft didn't work because the clay might have failed to hold the interlocking position.
  • An experiment testing one plant graft in interlocked position and one that is not could be carried out to test this theory. The plant graft in interlocked position should work and the one that is not should not work.
  • Keys to successful graft.
    • The plant graft must be held in interlocking position.
    • The clay should wrap around the connection so that water cannot leak out.
    • The string should tie around the plant graft firmly so that the interlocking position is kept until the graft is fully connected.

Sunday, December 11, 2016

[LAB] Thermochemistry (Ice Cream)

Objective: To observe the change in temperature through the making of ice cream.
Group: Guy, Shaq

Photos

Observation
  • Unfortunately, the base in the flask were never fully frozen before the lab is finished.
  • This might be caused by the lack of ice in the side of the tray where the flask is.


[LAB] Plant Structure

Objective: To observe structure of plants including leaves, stems, and roots in cellular scale.

Group: Guy, Shaq


Apparatus

Photos


Review Questions

  1.  If a plant's leaves have parallel venation, then we can expect to find root system of a monocotyledon. Xylem vessels would be arranged in a circular shape. We can also expect to find petals in multiple of 3 per flower.
  2. The node at the base of the petiole determines if the leaf is simple or compound. If the node is clearly present for one leaf, the leaf is simple. If multiple leaves branch out after a single node, however, the leaf is compound.
  3. A plant vein consists of two types of vascular tissue, Xylem and Phloem. Xylem transports water and minerals in an up direction away from the roots. Phloem transports sugar from the leaves to other parts of the plant.
  4. The primary function of the plant leaf is photosynthesis. It is adapted and specialized for turning carbon dioxide and water into glucose and oxygen through the help of light energy from the Sun.