Once Oxygen reaches the melting point, it turns into a liquid:

Liquid oxygen (picture above) is a pale blue liquid, extremely cold, and can only be made in specific lab conditions. Liquid Oxygen has no specific use in liquid form, but by turning oxygen into a liquid you can transport it more easily to use in medical or industrial facilities. The same applies to solid oxygen (picture below).

WHO FOUND OXYGEN AS AN ELEMENT?

Oxygen was found first by Carl Scheele, and 2 years later, by Joseph Priestly. Scheele found oxygen first as an element by experimenting with oxygen and air, as well as other periodic elements and fire (no documents of his precise work was found), and so did Priestly.

Priestly is mostly given credit, however, since he was the first to publish his work, and Scheele published his only after Priestly. Oxygen was found by Priestly in England, and Scheele in Sweden.

OXYGEN IN MEDICINE:

Oxygen has many uses in medicine. Very often, when somebody is in a coma or simply unconscious, they can't breath normally in their state, so oxygen must be provided for them. This means that the patient has a tube or mask on them, which supplies oxygen at proper rates, so the patient can live and breath normally.

Oxygen can restore tissue by stopping muscle or tissue of any sort get tense.

Oxygen can also help in medicine because it can help pregnant women when they are giving birth, since giving birth causes you to possibly hyperventilate or breath hard and rapidly. It can also help them by providing extra oxygen to the child (artificially) since babies often have a hard time breathing.

Oxygen in the air?

Oxygen and air are extremely similar. Air, as in what we breath in, is made of Oxygen, Nitrogen, and other gases, so we breath in Oxygen and Nitrogen.

Nitrogen and Oxygen both have liquid and solid forms, and are similar in how they act. Oxygen, like carbon, is essential for living, but while oxygen powers your body, carbon is part of your body.

HERE ARE MY SOURCES:

Google.com

URL: https://www.google.com/?gws_rd=ssl

Softschools.com

URL: http://www.softschools.com/facts/periodic_table/oxygen_facts/181/

Chemicool.com

URL: http://www.chemicool.com/elements/oxygen-facts.html

Sciencekids.co.nz

URL: http://www.sciencekids.co.nz/sciencefacts/chemistry/oxygen.html

Nfpa.org

URL: http://www.nfpa.org/research/reports-and-statistics/demographics-and-victim-patterns/medical-oxygen