“Chemical reaction vs. glass test tube” experiment
How to melt a test tube with the heat of the chemical reaction
It’s very important for chemists that the vessels they conduct experiments in are durable. But do reactions exist that can melt glass vessels?
Warning! Don’t try to repeat this experiment without a professional supervision!
Safety rules must be observed when working with flame and heated objects, and the experiment must be carried out in protective gloves, glasses and a mask.
Reagents and equipment:
- test tube;
- potassium nitrate (15 g);
- charcoal (1 g);
- sulfur (3 g);
- gas burner.
Fix the test tube to the stand, and put a funnel on it, through which we add potassium nitrate. Then melt the nitrate with the gas burner. Then add charcoal. It reacts with the potassium nitrate with the release of heat, but the test tube withstands this temperature onslaught. Then we add a few pieces of sulfur. The test tube becomes incandescent, and the glass sags and melts.
Potassium nitrate is a strong oxidizer. If it is melted, its strength increases from the release of oxygen in thermal breakdown:
2КNO₃ = 2KNO₂ + O₂
If charcoal is added to the test tube, it will react with the potassium nitrate with the release of a great amount of heat:
4КNO₃ + 5С = 2К₂CO₃ + 2N₂ + 3CO₂
Thus, the reactive mixture heats up to 900 °C (1652 °F, 1173 K). When sulfur is added, the reactive mixture heats up so much (1820°C, 3308 °F, 2093 K) that the temperature is sufficient for the glass test tube to melt.
2КNO₃ + 4S = К₂S + N₂ + 3SO2