Explain what the color differences of tubing AND test strip

Lab 2: Diffusion, osmosis and ose (1 point): solubility ections: 1. Fill a plastic cup with distilled (D) water to within 2cm of the top. 2. using a glucose test strip, test your cup for the presence of glucose. Is there glucose present? (yes or no). a. If glucose is present, empty out your cup. Wash the cup and start again from step 1. 3. Add 10-15 drops of Lugol\'s solution to plastic cup. THIS MuST BE coMPLETED IN THE HooD WEARING GLOVES. membrane. Tie a knot on 4. obtain a piece of dialysis tubing of 10cm. This will be used as your one end of the membrane. into the membrane. wmHANEw PlPETTE, 5. Using a transfer pipette, add 2-3mL of 2% starch other end. add the same volume of 20% glucose into the membrane Tie a knot on the is a leak, you 6. Gently invert your membrane a few times to ensure its contents are mixed. 7. Check if your membrane is leaking by gently squeezing your membrane. If there need to strengthen your knot. initial volume of 8. Place membrane into cup. Mark the level of the 9. Note the initial volume of liquid in the membrane. water in your cup. minutes. 10. Allow membrane to sit for 30 1. Why are we using Lugol solution? What does Lugol\'s solution test for? (2 points). solut insid the tube with starch want to act on

Solution

Ans. Results obtained:

A. Solution inside dialysis tube turns from colorless to pink after incubation period.

            Conclusion: It indicates that Lugol’s solution diffused from cup into the dialysis tube.

B. The water in cup tests positive for glucose after incubation period.

            Conclusion: Glucose diffused from dialysis tube into the water (cup).

Diffusion: It is movement of a solute from its higher to lower concentration gradient. Since, there is movement of solutes from their respective higher to lower concertation [A. Lugol’s solution: from cup (higher conc.) to tube (initial conc. = 0) ; B. Glucose: from tube (higher conc.) to cup (initial conc. = 0)], the experiment illustrates the process of diffusion across the membrane.

Osmosis: Osmosis is the movement of water (solvent) from its higher to lower gradient across a semi-permeable membrane. It’s assumed that tube acts as membrane. Note the change if initial water level in the cup increases/decreases. Any change in water level means that there is movement of water between tube and cup. That is, the process of osmosis has occurred.

Note: Change in water level is NOT mentioned in question. It’s assumed that it changed during incubation period.