Sand Termite

Silicon crystals are born in a blue flame.

Scientific name: Silicon dioxide burns with aluminum powder producing silicon and aluminum oxide.

YouTube

Make Thermite out of Sand

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Thermite reaction with sand and sulfur

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Isolation of Silicon (Thermite with Sand)

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Safety

Wear eye protection goggles and gloves. There is a serious fire risk - a fire extinguisher should be ready. Make sure there is nothing flammable nearby.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

2Al + 3S → Al2S3

4Al + 3SiO2 → 2Al2O3 + 3Si

Step-by-step instruction

WARNING! This experiment is dangerous! You should NOT perform this at home. ONLY carry out this experiment, if you are a trained chemist, and you understand local safety and legal requirements, which are required to perform such experiments

  1. To make sand thermite prepare the following components: sand, aluminum powder and sulfur.
  2. For better result the common sand should be treated with diluted hydrochloric acid to remove all the impurities. After treating rinse the sand with water.
  3. Grind each substance in a mortar to get a finer powder.
  4. Mix the components in the following ratio: 9 parts of sand, 12 parts of sulfur and 10 parts of aluminum.
  5. Prepare a strong container (a clay flower pot for example).
  6. Fill it by half with sand.
  7. Pour the sand, sulfur and aluminum mixture into the pot in a hill-like shape. Make a socket on top of the hill.
  8. Place a few grams of potassium permanganate into the socket and insert the magnesium strip.
  9. Set the pot with the termite mixture outdoors in a safe place. Make sure that there are no flammable materials nearby.
  10. Put the few drops of glycerin on top of the pill to cover the magnesium strip.
  11. The mixture will burn in a few minutes with a bright blue flame and evolution of a large amount of heat.
  12. Let the pot to cool down.
  13. The large chunk of solid substance was formed in the thermite reaction. To obtain pure silicon break down the chunk and treat it with diluted hydrochloric acid. Then rinse it with water and dry. These operations also should be performed outside because the presence of sulfur compounds.

Scientific background

Thermite is a class of exothermic reduction-oxidation reactions. They are characterized by extremely high temperatures generated. As a rule termite composition consists of metal powder which plays a role of a fuel and metal oxide. In the described experiment elemental aluminum reduces the silica oxide (sand). In this reaction silica oxide behaves itself like a metal oxide besides the silicon properties lie in between metals and nonmetals. As a result the metallic silica and aluminum oxide are formed.

It is not easy to make aluminum and silica oxide react since the activation energy of this reaction is very high. The energy needed to overcome the activation barrier can be supported by heat produced in another reaction. The side reaction of sulfur and aluminum is used for this purpose. These components react much more readily with evolution of heat enough to start the main reaction. The presence of sulfur causes the blue color of thermite flame and the special smell of the produced smoke.

The initial ignition of the mixture is also made chemically. The reaction of potassium permanganate and glycerin produces fire without matches which ignites the magnesium ribbon which in turn runs the reaction between sulfur and aluminum. The chain ends on the target reaction between silica oxide and aluminum.

Danger:
Coolness:
Difficulty:

Published on 09 September 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst