Joanne Hennessy, age 11, of Albany, N. ., or her question:

Can the gases be separated from the air?

Air, of course, is a mixture of gages and it is possible to sort them apart. The job can be done in countless different ways and new methods of taking this or that gas from the air are constantly being invented by the chemists. It is usually a complicated job and often done step by step.

Sometimes chemicals are used, sometimes an electric current. The mixture also can be separated by chilling, for each gas turns to liquid at its own particular temperature. A gas may be chilled to its liquid state with the help of pressure, squeezed tight and then released. To take liquid oxygen from the gaseous mixture, we would chill to minus 118 degrees and put on pressure equal to 49 atmospheres.