Question

if you put a dialysis bag filled with starch in a beaker that contain iodine your bag turn brown because __________.

water diffuse into bag and turn starch brown.
plastic in dialysis bag react with water and change color.
water diffuse out of the bag and turn starch brown.
lodine diffuse into bag and turn starch brown.

Explanation:

🆕 New Concept Discovered: Selective Permeability and Diffusion
Molecules move based on size across membranes

Step 1: Understand the setup

A dialysis bag acts as a semipermeable membrane. It has tiny pores that allow small molecules to pass through while blocking larger molecules.

• Inside the bag: Starch (a very large polysaccharide molecule).
• Outside the bag (in the beaker): Iodine (a very small molecule) dissolved in water.

Step 2: Determine which molecules can move

Because of the size of the pores in the dialysis tubing:

• Starch is too large to pass through the membrane and must stay inside the bag.
• Iodine is small enough to pass freely through the membrane.

Since there is a high concentration of iodine outside the bag and none inside, iodine molecules will diffuse down their concentration gradient, moving from the beaker into the dialysis bag.

Step 3: Identify the chemical reaction

When iodine comes into contact with starch, a chemical reaction occurs that changes the color of the solution to a dark blue, black, or deep brown/purple color. Because the iodine moves inside the bag where the starch is trapped, this color change happens inside the bag.

Answer:

Iodine diffuse into bag and turn starch brown.