Learning Aims:
  • To transfer their macroscopic knowledge onto the invisible level of atoms and molecules.
  • To develop a better understanding of the particulate nature of matter.
  • To show the existence of molecules and that they have different sizes.
  • investigate different pore sizes within plastics/polymers
  • Red food dye solution
  • Iodine-Starch Solution
  • Potassium Permanganate Solution
  • Iodine-Dextrin solution
  • Iodine Solution (Just for Part 2)
  • Iodine Solution (Just for Part 2)
  • 4 Rubber bands
  • 5x50ml beakers
  • 4 lengths of visking tubing
  • 5 sheets of cling film
  • 10ml plastic dropper
Suggestions for use:

Procedure Part 1

  • Prepare a 1% starch solution with water at 70°C
  • Add iodine and leave iodine and starch solution to one side (Turns blue)
  • Add 0.5g of dextrin to 100ml of water and then add a few drops of iodine (Turns red)
  • Open the visking tubing lengths by holding it under running water for a few minutes. Tie one end with an elastic band tightly. Ensure the elastic band is stretched very tightly so that no liquid leaks out.
  • Add a different solution (from list of chemicals above) into each of the four lengths carefully using a dropper. Stick the dropper to the bottom of the visking tubing and release the solution. Make sure none of the solutions touch the outside membrane. Tie off the other end of the visking tubing firmly with an elastic band.
  • Submerge each tube into different beakers of water.
  • Record what is observed over 10 minutes.
  • Wash all glassware and dispose of visking tubing.

Procedure Part 2

  • Repeat this experiment using cling film instead of visking tubing as follows:
  • Fill 5 beakers with water and loosely place strips of cling film over the top allowing the cling film to touch the water. Try not to stretch the cling film. Secure the edges of the cling film around the side of the beaker.
  • Add a different solution onto each of the five cling film strips resting on the beakers. Make sure the solutions do not overflow the sides of the beakers.
  • Leave overnight and record your observations the following day.
  • Compare and contrast the results from part one and two and suggest reasons for your findings.