- 50 g sulfur [Compare Prices]
- test tube (25 mm x 200 mm)
- test tube clamp
- beaker of water (500 mL or so)
ProcedureYou'll melt the sulfur, which changes from a yellow powder into a blood-red liquid. When the molten sulfur is poured into the beaker of water, it forms a rubbery mass, which remains in polymer form for a variable length of time, but eventually crystallizes into a brittle form.
- Fill the test tube with pure sulfur powder or pieces until it is within a couple of centimeters of the top of the tube.
- Using a test tube clamp to hold the tube, place the tube in a burner flame to melt the sulfur. The yellow sulfur will turn into a red liquid as it melts. The sulfur may ignite in the flame. This is fine. If ignition occurs, expect a blue flame at the mouth of the test tube.
- Pour the molten sulfur into a beaker of water. If the sulfur is burning, you'll get a spectacular burning stream from the tube into the water! The sulfur forms a golden-brown "string" as it hits the water.
- You can use tongs to remove the mass of polymer sulfur from the water and examine it. This rubbery form will last anywhere from a few minutes to several hours before reverting to the usual yellow brittle rhomic crystalline form.
How It WorksUsually sulfur occurs in orthorhomic form as eight-membered cyclic rings of monomeric S8. The rhomic form melts at 113°C. When it is heated over 160deg;C, sulfur forms high molecular weight linear polymers. The polymer form is brown and consists of polymer chains containing about a million atoms per chain. However, the polymer form is not stable at room temperature, so the chains eventually break and reform the S8 rings.
- The sulfur is safe to recycle or dispose in any waste container.
- Use care when handling the plastic sulfur, as it may still be hot/molten for several minutes.
- It's best to perform this project under a hood or outdoors, since sulfur dioxide (SO2) will be released if the sulfur ignites. Sulfur dioxide is a greenhouse gas, which is irritating and toxic.
Source: B. Z. Shakhashiri, 1985, Chemical Demonstrations: A Handbook for Teachers of Chemistry, vol. 1, pp. 243-244.
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