Substance is like oxygen pass through the cell without the use of energy and move from an area of high concentration to an area of low concentration. This process is called

This process should be known as diffusion.

Diffusion is the process in which a substance moves from an area of high concentration to a an area of low concentration. Oxygen is a good example, like in your question, because it can have a high concentration outside the cell, and a low concentration inside the cell. And so, no energy is needed for the cell to move within the lipid bilayer.

The process is diffusion.