LIQUID OXYGEN

Shown above is a mixture of liquid O2 and O3 (ozone). O3 condenses to a dark blue fluid (bottom layer) at −112 °C, and O2 to a lighter blue liquid at −183 °C. Both liquids are powerful oxidizers. Liquid Ohas applications in aerospace propellants and explosives, but liquid O3 is less useful because it can easily detonate when it reaches its boiling point. On an open lab bench, a flask like this is a safety hazard. 

Credit: periodictable.ru

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A really spectacular experiment: ignition of ground coffee. 

If anyone would ignite some ground coffee not this result would be obtained. The trick was that we previously liquefied some oxygen, added the ground coffee (ATTENTION: it could explode!) and then poured out this ground coffee/liquid oxygen mixture in a porcelain crucible. When the liquid oxygen evaporated, the coffee was lit and it burned as a rocket fuel (as seen on the pics).

Something interesting: Coffee beans have a high potassium content as seen from the color of the flame. 

Oxygen absorbing material may allow us to breathe underwater
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Using specially synthesized crystalline materials, scientists from the University of Southern Denmark have created a substance that is able to absorb and store oxygen in such high concentrations that just one bucketful is enough to remove all of the oxygen in a room. The substance is also able to release the stored oxygen in a controlled manner when it is needed, so just a few grains could replace the need for divers to carry bulky scuba tanks. The key component of the new material is the element cobalt, which is bound in a specially designed organic molecule. In standard form – and depending on the available oxygen content, the ambient temperature, and the barometric pressure – the absorption of oxygen by the material from its surroundings may take anything from seconds to days. “An important aspect of this new material is that it does not react irreversibly with oxygen – even though it absorbs oxygen in a so-called selective chemisorptive process,” said Professor Christine McKenzie from the University of Southern Denmark. “The material is both a sensor, and a container for oxygen – we can use it to bind, store, and transport oxygen – like a solid artificial hemoglobin.” (via Oxygen absorbing material may allow us to breathe underwater)