Difference between revisions of "Chemical demonstrations"

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(Alkali metals)
 
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==Alkali metals==
 
==Alkali metals==
 
===In the presence of water===
 
===In the presence of water===
[[Lithium]] will effervesce strongly
+
[[Lithium]] will effervesce strongly and may ignite;
  
[[Sodium]] will do so more strongly and may catch fire
+
[[Sodium]] will do so more strongly and more often than not catches fire, potentially exploding when in large amounts;
  
[[Potassium]] catches fire
+
[[Potassium]] catches fire and almost always explodes;
  
[[Rubidium]] and [[caesium]] will explode.
+
[[Rubidium]] and [[caesium]] will explode unless added in tiny amounts.
  
 
[https://www.youtube.com/watch?v=uixxJtJPVXk Video: Alkali metals reaction with water]
 
[https://www.youtube.com/watch?v=uixxJtJPVXk Video: Alkali metals reaction with water]

Latest revision as of 20:04, 16 October 2022

Chemical demonstrations that are amusing or impressive to watch.

Energetic materials

Explosive decomposition of Para-nitroaniline

Para-nitroaniline explodes, leaving an impressive mount of carbon behind under the attack of hot concentrated sulfuric acid.

Video: P-nitroaniline's decomposition demonstration

Mercury thiocyanate ("Pharaoh's serpent")

Mercury(II) thiocyanate burns forming residues looking like tentacles growing from the ground.

Video: mercury thiocyanate's combustion demonstration

Video: Mercury thiocyanate and ammonium dichromate's combustion. "gates of hell" effect demonstration

Ammonium dichromate ("Volcano")

When ammonium dichromate burns, it looks like an erupting volcano.

Video: ammonium dichromate's combustion demonstration

Iodine and aluminium

When aluminium and iodine are combined in the presence of a small amount of water, they react to produce thick purple smoke and leaves a metallic coating on the glass.

Video: Iodine and aluminium demonstration

Color changes

Briggs-Rauscher oscillator

Very pronounced and rapid color changes repeating again and again and again.

Video: iodine oscillator demonstration

Iodine clock reaction

Colorless solutions becoming deep blue/black almost instantaniously after a small delay.

video: iodine clock demonstration and theory

Chameleon

5 vivid color changes in a row while the reaction passes through the many different oxidation states of manganese.

Video: Chameleon demonstration

Light emission

Fluorescent pH indicator

Pyranine, present in highlighter fluid, will fluoresce different colors in different levels of acidity.

Smash-glow crystals

Sugar will emit ultraviolet light when crushed. When a fluorescent dye such as methyl salicylate is used, the fluorescence is made much brighter.

Miscellaneous

Elephant toothpaste

The rapid decomposition of hydrogen peroxide with a catalyst (usually potassium iodide or yeast) in soapy water generates a huge amount of hot foam due to oxygen generation.

Video: Elephant toothpaste demonstration

Carbon snake

Materials needed: granular sugar and concentrated (98%) sulfuric acid, acid resistant gloves

Procedure: Pour concentrated sulfuric acid directly onto sugar.

Result: a tower of porous carbon forms after a delay period.

Video: carbon snake demonstration

Alkali metals

In the presence of water

Lithium will effervesce strongly and may ignite;

Sodium will do so more strongly and more often than not catches fire, potentially exploding when in large amounts;

Potassium catches fire and almost always explodes;

Rubidium and caesium will explode unless added in tiny amounts.

Video: Alkali metals reaction with water

See also

References

Relevant Sciencemadness threads