what is iodine solution changing from amber-yellow to blue-black an indication of?

Abstruse:

This experiment was conducted to investigate the selective permeability of dialysis tubing. The permeability of the tubing to glucose, starch and iodine (potassium iodide) was tested. The dialysis tubing was clipped to form a bag then that glucose and starch was fed into the bag through the other end, and was also clipped to avert the seeping of the solution.

Water with several drops of iodine added to information technology until information technology was visibly yellowish-amber was added to a 400ml beaker. The purse was then placed in the beaker, which was stirred with a magnetic stirrer. Information technology was left there for 30 minutes. It was seen that the colour of the solution in the bag inverse to blueish-black color, this showed that iodine was able to pass through the membrane into the bag.

The solution in the chalice became pale yellowish-amber, this showed that starch didn't pass through the membrane into the beaker. To confirm the presence of glucose in the beaker and too the bag, a Benedict test was performed on the solutions including tap water (control) too.

The beaker solution turned into light brown color after Benedict solution was added to it and suspended in water bath for x minutes. The purse solution also changed to brownish color, while tap h2o remained blue. This experiment showed that dialysis tubing is selective in its permeability to molecules. It was permeable to glucose and iodine but non starch.

INTRODUCTION:

PURPOSE: The purpose of the experiment was to test the permeability of dialysis tubing to glucose, starch and iodine.

Living cells need to obtain nutrients from their environment and get rid of waste matter materials to their surroundings. This exchange of materials betwixt the cell and its environment is crucial to its being. Cells have membranes equanimous of a phospholipid bilayer embedded with proteins.

This cell membrane can distinguish between different substances, slowing or hindering the movement of other substances and allowing others to laissez passer through readily. This property of the cell is known as selective permeability (Ramlingam, 2008).

Selective permeability is a belongings of a prison cell membrane that allows it to control which molecules can laissez passer (moving into and out of the jail cell) through the pores of the membrane. Selective permeable membranes just allows small molecules such as glucose, amino acids to readily pass through, and inhibits larger molecules like protein, starch, from passing through it.

The dialysis tubing is a semi-permeable membrane tubing used in separation techniques and demonstration of diffusion, osmosis, and motility of molecules across a restrictive membrane (Todd, 2022). Information technology separates dissolved substances of different molecular sizes in a solution, and some of the substances may readily laissez passer through the pores of the membrane while others are excluded. The dialysis tubing is fabricated up of cellulose fibers. This is shaped in a apartment tube.

In this experiment, the selective permeability of dialysis tubing to glucose, starch and iodine (potassium iodide) will exist tested. This experiment consists of two tests; the test for starch and the test for reducing sugar. When iodine (potassium iodide) is added to a solution in which starch is present, the solution turns blue-blackness or purple otherwise it remains yellow-amber.

And when Benedict's reagent is added to a solution in which reducing sugar is nowadays and information technology is heated in a water bath, the solution turns green, xanthous, orange, reddish, and then brick red or brown (with high concentration of sugar present). Otherwise, the solution remains blue.

QUESTION:

Will glucose, starch and iodine (potassium iodide) readily pass through the pores of the dialysis tubing?

HYPOTHESIS:

Glucose, starch and iodine (potassium iodide) will readily pass through the membrane of the dialysis tubing.

PREDICTION:

The solution in the bag and the beaker will both turn bluish-blackness due to the presence of iodine and starch; the presence of glucose in the pocketbook and beaker will exist investigated using Benedict test.

MATERIALS:

• Beakers
• Dialysis Tubing
• Test Tubes
• Exam Tubes rack
• Clips
• Water Bath
• Water

SOLUTIONS:

• Benedict'southward reagent
• Glucose
• Starch
• Iodine (Potassium Iodide)

EXPERIMENT PROCEDURE:

ane) 250 ml of tap water was added to a beaker. Several droppers of Iodine (Potassium Iodide) solution was added to the water until information technology was visibly yellowish-amber in color. The color was and then recorded.

two) The dialysis tubing was soaked in water for a few minutes until it began to open. One end of the bag was folded and clipped in order to secure it so that no solution seeped through.

3) The other end of the tubing was opened so that it forms a pocketbook and 4ml of glucose and 3ml of starch was fed into it. The bag was also closed and its content was mixed. The color of the solution was then recorded.

four) The exterior of the bag was rinsed in tap water.

5) The magnetic stirrer and so the bag was placed in the chalice. The other terminate of the handbag was fabricated to hang over the edge of the beaker.

vi) The bag was left in the beaker for virtually thirty minutes, as the beaker was being stirred.

7) Later on xxx minutes, the bag was carefully removed and fabricated to stand in a dry out beaker. The final color of the solutions was recorded.

viii) Benedict examination was performed to exam for the presence of reducing carbohydrate in the solution in the bag, beaker and tap water (serves as control).

1. a) 3 test tubes were labelled control, pocketbook and chalice.
2. b) 2 ml of water was added to the control test tube. 2 ml of the bag solution was added to the bag examination tube and 2 ml of the beaker solution was added to the beaker examination tube.
3. c) 2 ml of Benedict'southward reagent was added to each examination tube and was suspended in a boiling water bathroom for 10 minutes. The color change was recorded.

RESULTS:

Solution Source	Original Contents	Original Color	Last Color	Color after Benedict's test
Bag	Starch and Glucose	Colorless	Blue-black	Chocolate-brown
Beaker	Water and Iodine	Yellow-amber	Pale yellowish-bister	Brownish
Control	Water	Colorless	Blue	Blue

The solution in the bag turned bluish-black in colour owing to the motion of molecules of iodine from the chalice to the bag which contains starch. The solution in the chalice turned brown later on Bridegroom's exam.

This indicated the presence of glucose in the beaker. This ways that the tubing was permeable to both glucose and iodine simply not starch. It is known that starch didn't pass considering the solution in the beaker which contains iodine didn't turn bluish-blackness in colour, simply remained xanthous-amber.

DISCUSSION:

i) How can you explain your results?

From the results of the experiment represented in a tabular class in a higher place, the hypothesis suggested before conveying out the experiment turned out to be incorrect. The dialysis tubing was not permeable to all the three solutions- glucose, starch and Iodine (Potassium Iodide). Rather, the tubing was permeable to glucose and iodine but not starch.

This could exist known from the colour modify in the solutions in the beaker and the bag. The tubing was permeable to iodine and so the content of the bag turned blue-black in color indicating the presence of starch. Glucose too readily passed through the pores of the membrane.

After performing Benedict's test on the solutions, the bag's solution besides as the chalice's solution turned brown in color. This shows the presence of reducing sugar in both solutions, significant that glucose passed into the chalice from the handbag.

2) From your results, predict the size of Iodine (Potassium Iodide) relative to Starch.

From the results of this experiment, it is obvious that glucose and iodine (potassium iodide) has smaller molecular size than starch. Because starch had larger molecular size, the dialysis tubing was not permeable to information technology (information technology didn't allow it to readily laissez passer through the pores of its membrane).

3) What colors would you expect if the experiment started with glucose and iodine (potassium iodide) within the bag and starch in the chalice? Explain

* The solution in the bag will remain yellow-amber in color at the terminate of the experiment.

* The solution in the beaker will plow blue-blackness in colour at the end of the experiment.

* Subsequently performing benedict test, both solutions volition turn brown in color.

The solution in the bag remained yellowish-bister in color at the terminate of the experiment because the dialysis tubing is not permeable to starch and so starch didn't pass through from the beaker into the handbag.

The solution in the beaker turned blueish-black in color at the end of the experiment because iodine passed from the bag into the chalice through the membrane.

After performing Benedict's examination on the pocketbook and beaker solution, both solutions turned brown in color because the tubing was permeable to glucose, so glucose readily passed from the bag into the beaker through the membrane.

PRECAUTIONS:

• Information technology was ensured that the right quantity of solutions was used in every function of the experiment.
• It was as well ensured that the time required for the successful complement of the experiment was adhered to.
• It was ensured that all apparatus used were handled with circumspection.
• And too, the dialysis tubing was clipped well on both ends to secure it so that no solution seeped through.

CONCLUSION:

It was concluded that the dialysis tubing doesn't allow all kinds of substances to pass readily through the pores of its membrane. This means that it is selective in its permeability to substances. The dialysis tubing was permeable to glucose and iodine simply not to starch. Starch was excluded because it has a larger molecular size than glucose and iodine.

References

Ramlingam, S. T. (2008). Modern Biology. Onitsha: African First Publishers.

Todd, I. S. (2012). Dialysis: History, Development and Hope. World Scientific Publishing Co Pte Ltd.

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