| MadSci Network: Chemistry |
Hydrogen and oxygen combine to form either water (H2O) or hydrogen peroxide (H2O2). Since water is the most likely product, let's focus on it.
In reacting to form water, hydrogen and oxygen release energy in an exothermic reaction. Thermodynamics tells us that the amount of energy released is dependent on the temperature of the hydrogen/oxygen/water system. Thermodynamics further tells us that the relative amounts of water, hydrogen and oxygen are dependent on this amount of energy released. I could not find data at liquid hydrogen temperatures, but extrapolations of the available data showed that essentially no reaction would occur at these extremely low (<25 K) temperatures. So what you would have would be simply a mixture of liquid hydrogen and oxygen that would probably be similar to a mixture of oil and water.
Please note, I am making several assumptions and extrapolations in this answer. If, for example, mixing the liquid oxygen and hydrogen released energy from the mixing process, you could raise the temperature to the point where you get a significant reaction that further raises the temperature and promotes further reaction until the reaction is completed. I am assuming isothermic conditions are maintained at liquid hydrogen temperatures and the oxygen is cooled to that temperature before mixing with the hydrogen.
If you do form any water, there are extremely low temperature forms of ice that are different in how the molecules are arranged compared to "normal" ice. Pressure can also affect the form of ice. In your local library look for a phase diagram for ice. This will give you more detailed information. Universities such as the University of Minnesota have extensive research programs dealing with ice. Most are either in the Materials Engineering or Physics Departments.