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Starch and Iodine Demonstration
Starch and Iodine Demonstration
The change in colour of the starch solution around the edges of the ziploc bag demonstrates the semi-permeable membrane of the ziploc bag. This acts like the cell membrane as the iodine can enter the bag, but the starch solution cannot exit through the plastic.
1) Make a starch solution (150ml water, 2 tsp of starch)
2) Fold the edges of a ziploc bag open and pour 4 tsp of starch solution into the bag and seal it, making sure there is little to no air in the bag.
3) Take a piece of string and tie it around the plastic bag.
4) Tie the string to a popsicle stick or a dowel (so that the bag does not completely fall into the iodine solution)
5) Make an iodine solution in a clear beaker (10 drops of iodine into 150ml of water).
6) Place the bag of starch solution that is attached to the dowel into the iodine solution.
7) Wait 30 minutes and observe the change in colour on the inside of the ziploc bag of starch solution. Open the bag up with the class surrounding the teacher to investigate the colour on the edges of the bag.
Gummy Bear Osmosis Demonstration
Gummy Bear Osmosis Demonstration
When a gummy bear is placed in a beaker full of water, sugar water, and salt water what will happen? The gummy bear in the water will expand, the bear in the salt water will shrink, and the one in the sugar solution will stay the same. Why? The gelatin acts as a cell membrane, allowing water to go into the gummy bear. The addition of salt and sugar affects the flow of water into and out of the gummy bear.
1) Make a concentrated sugar solution and a concentrated salt solution
2) Measure out 150ml of each solution and 150ml of water into 3 beakers
3) Place one gummy bear in each solution
4) Soak gummy bears overnight
5) Remove gummy bears carefully with a spoon (the bears may be fragile)
6) Discuss the change in the size of the gummy bears from each solution. How was osmosis affected by the different solutions?
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