It’s time for another edition of Sidechain’s favorite chem demos. The one I’ll be describing today holds a place near and dear to my heart. When I was a young high schooler (a shorter polypeptide… get it?), my high school chem teacher showed this to our class. She had a glass of what looked like water. She poured it into a wine goblet, and the water turned to wine (cool, right!). She then poured the ‘wine’ into another glass, where it became ‘milk’, which when poured into the final glass turned into ‘beer.’ When I first saw this, I really thought it was magic. It turns out that the chemical principles are pretty simple! All the student really needs to understand is acid-base chemistry, indicators, and precipitates. Anyway, here’s what you’ll need:
- Glass #1: 0.1 M Sodium Carbonate (NaHCO3). What I did was make 100mL of a stock solution and add around 50mL to a clear water glass.
- Glass/Goblet #2: A few drops of phenophtalein in the bottom of a long-necked wine glass. I usually use a plastic one and put some tape on the bottom to cover the indicator solution.
- Glass #3: 5mL 1.0M BaCl in the bottom of a clear glass with some tape on the bottom.
- Glass #4: 5mL 12M HCl and 5mL of bromothymol blue indicator, at the bottom of a pint glass/plastic clear solo cup
So if you can’t guess, the science behind this is pretty simple.
- Sodium Carbonate is a basic solution that looks like water
- Adding phenothalein will make the solution purple, and look like wine
- Adding Barium ions will precipitate out a suspension of Ba(OH)2, which will look like an opaque white liquid (milk!)
- In the last cup, the concentrated acid will (a) acidify the remaining base, eliminating the Ba(OH) (b) result in the evolution of CO2 gas and (c) make a beer-like color with the indicator
This demonstration is pretty easy to explain to a group of first-year chemists, and is a great application of the skills they have already learned! Just remember not to drink any of these liquids, especially the “beer” (no matter how tempting it may be!)
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