Liquid oxygen is sky blue and solid oxygen is blue crystal. Oxygen is not active at room temperature, but it can combine with many elements at high temperature. Oxygen is widely distributed and widely used in nature. Animals need to consume oxygen when they breathe and burn. Liquid oxygen air separation plant is widely used in industry and military. Because of its low temperature, liquid oxygen will become brittle when it contacts with other substances. Liquid oxygen is also a very strong oxidant: organic matter burns violently in liquid oxygen.
