A glass filled with what looks like water is poured into a second glass, where it "magically" turns into wine. When the wine is poured into a third glass, it changes to milk, and when the milk is poured into a fourth glass, it changes to beer!
The "water" in the first glass is really a solution of sodium carbonate (Na2CO3), also known as washing soda. The carbonate ion causes the solution to be alkaline, that is, it is a weak base that produces hydroxide ions (OH-).
The second glass contains several drops of phenolphthalein indicator. An indicator is a substance that is a different color in acidic solution than it is in basic solution. Phenolphthalein is colorless by itself, but when the alkaline "water" is poured into the glass, it turns pink, giving a solution that looks like a light red wine.
The third glass contains a saturated solution of barium chloride (BaCl2). When the "wine" is poured into the glass, the carbonate ions in the solution react with the barium ions to form barium carbonate (BaCO3), a white solid precipitate. The suspension of white solid in the solution makes it look like milk.
The fourth glass contains concentrated hydrochloric acid (HCl) and some bromthymol blue indicator. When the "milk" is poured into this, the barium carbonate reacts with the acid, forming soluble barium ions, water, and carbon dioxide gas. The white solid dissolves, the carbon dioxide creates bubbles, giving the solution a "head," and the bromthymol blue, yellowish-brown in acidic solution, gives the color of beer.
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explanation furnished by UCCS's