Diffusion Lab – Iodine & Cornstarch

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Materials and Set Up –this was so easy and inexpensive to do and had the same effect as using dialysis tubing.Great demo/lab as part of our unit on osmosis and diffusion!

For every two students:

  • 生物角讲义
  • large beaker
  • 便宜的三明治袋——非密封(我用的是Wegmans 150 CT)
  • 1 tbsp corn starch
  • 50 mL water
  • 橡皮筋
  • clothes pin
  • graduated cylinder
  • 100 mL Iodine dilution


  • 20 ml Iodine added to 500 mL of water
  • 测量每组100毫升稀释碘

Prelab Prep:

  1. 在每个烧杯上放一个袋子
  2. Add 1 tbsp of cornstarch to each bag
  3. Add 50 mL of water to each bag
  4. 检查渗漏
  5. 用橡皮筋把每一个都绑紧
  6. Clip bag to beaker


  1. 学生们将添加碘并进行观察——变化将在几分钟内发生,时间越长,the darker it will become.
    1. Iodine is able to pass through the plastic bag,淀粉不是
  2. Have students lift the bag out to see the changes that are taking place
  3. 讨论

更新– I let the set up sit over the weekend,and when I came in today,水几乎完全清澈——看起来几乎所有的碘都被转移到了袋子里:William Hill轮盘



2 thoughts on "Diffusion Lab – Iodine & Cornstarch"

  1. 克里斯汀·康诺利 October 7,2018 / 6:58 pm

    Hi,我正和七年级的学生一起完成渗透和扩散的研究。奇怪的是,I tried this very set up hoping that inexpensive baggies would work.We had tried with a z-loc brand bags and had no luck ( just letters to the company letting them know how non permeable their baggies were) so I used the store brand baggie and we were still disappointed.我想我们都对包裹在这些袋子里的三明治感觉好一些,但没有William Hill轮盘看到扩散。我们用胡萝卜和盐做了一个伟大的调查,然后转向“裸蛋”。I had been very hopeful the baggie would work.Glad it did for your crew.


    • Liz LaRosa October 7,2018/7:13

      We used either Wegman's brand fold over sandwich bags or ShopRite – I threw out the box without writing it down -Sorry it didn't work for your class
      The carrots sounds like a great idea,我看到一个用土豆片,我也想过用。William Hill轮盘I have never tried the egg one,但听说效果很好

      Update – it was Wegmans brand,box was still in my room


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