Can someone me
what happens to oxygen at -183 degrees celsius?

Oxygen is like a milder form of nitrogen when it comes to its changing forms.

Oxygen becomes a gas when heated above -183 degrees Celsius, and when it is cooled below -183 degrees Celsius, it becomes a liquid. 

Just as a bonus, the transition between liquid and solid forms happens when Oxygen is cooled below -218.79 degrees Celsius.

So your answer is "the conversion between the liquid and gaseous states of Oxygen." :)

Oxygen turns into a liquid at -183 Celsius
to get the oxygen to such a lower temperature, the gas is compressed and then cooled 

Independent variable is something that is changed in a experiment.