At what temperature does oxygen solidify?

At room temperature, oxygen is a colorless and odorless gas that is heavier than air. Oxygen belongs to the chalcogen family and forms diatomic molecules O2. The ability to form molecules between atoms of the same type also occurs in the other chalcogens. At −182.97 ° C, oxygen condenses into a light blue liquid.


Liquid oxygen
 

 
Gaseous oxygen is passed through a cold trap cooled with liquid nitrogen. After a while, liquid oxygen is formed, which can be recognized by its light blue color. If you drink a cigarette with it, you get a small cutting torch after lighting it.

 
Oxygen is slightly soluble in water and in ethanol. The water solubility decreases with increasing temperature. This explains why fish can suffocate if the water temperature rises even slightly. The highest oxygen solubility with just over 14 milligrams per liter has pure water at the freezing point. The maximum solubility also depends on the dissolved salts in the water: In seawater, only about 8 milligrams per liter of oxygen are soluble at 0 ° C. If the water is saturated with air, only 10.3 milligrams per liter dissolve in fresh water at 0 ° C.
 
 
Oxygen solubility in pure water
 

 
The maximum solubility depends on the water temperature.
   

In contrast to nitrogen, oxygen is very reactive and intensifies burns. It burns most of the elements such as iron or sulfur under the appearance of fire and light to form their oxides. A very violent reaction occurs with the element cerium. This creates temperatures of up to 4000 ° C.
  
3 Fe + 2 O2  Fe3O4    ΔHR. = −1118 kJ / mol 
S + O2  SO2               ΔHR. = −297 kJ / mol 
Ce + O2  CeO2          ΔHR. = −975 kJ / mol    
  
 
Cerium iron reacts with pure oxygen
 

 
If you hold a glowing flint in pure oxygen, a very violent reaction ensues.
   
An extremely high, chemically attainable temperature of over 4660 ° C is obtained when burning zirconium powder or zirconium wool in pure oxygen:

Zr + O2  ZrO2     ΔHR. = −1101 kJ / mol 
  
Such reactions are called oxidations. Oxidations include burns, but also the rusting process or breathing. The higher the oxygen concentration, the more violent the reaction. It usually needs activation energy to ignite. A loud bang occurs after the ignition of a hydrogen-oxygen mixture in a ratio of 2 to 1. This oxyhydrogen reaction produces water vapor as a reaction product.
  
Oxygen atoms occur in numerous chemical compounds, for example in inorganic mineral acids such as phosphoric acid, nitric acid or sulfuric acid and their respective salts, in alkalis, in alcohols such as methanol or ethanol, in aldehydes such as formaldehyde, in ketones such as acetone and organic acids such as methanoic acid or ethanoic acid.
 
In the laboratory, gaseous oxygen is detected with the Glimmspan sample. To do this, you light a piece of wood, let it glow for a while and then blow out the flame again. If you hold the glowing chip in a container with pure oxygen, the chip ignites again. When a piece of glowing charcoal is dipped into a standing cylinder filled with oxygen, the charcoal will also start to burn. Blowing with a bellows on a fire adds more oxygen from the air, thereby increasing the fire.


Glimmspan and iron wool in pure oxygen
  

 
A smoldering wood chip flares up in pure oxygen. The iron wool burns under spark spray.


When chlorine is passed through an alkaline hydrogen peroxide solution in a gas washing bottle with a frit, a hypochlorite ion is formed. This reacts with the hydrogen peroxide to form a chloroperoxide ion, which splits off the chloride Singlet oxygen forms. This represents an energetically stimulated form of oxygen. When it is converted into normal triplet oxygen, energy is released that we perceive as red light. In the case of singlet oxygen, the spin of the electrons is aligned antiparallel.


Singlet oxygen
Chlorine is passed through a frit into a strongly cooled, alkaline hydrogen peroxide solution.
A red glow can be seen in the dark.