* Increase in pressure: As the volume decreases, the molecules collide more frequently with the container walls, leading to a higher pressure.

* Decrease in volume: This is the very definition of compression – the molecules are squeezed into a smaller space.

* Increase in density: With more molecules packed into the same space, the density of the gas increases.

* Increase in temperature (if adiabatic): If the compression occurs quickly and without heat transfer (adiabatic), the molecules gain kinetic energy from the collisions, causing the temperature to rise.

Important note: The behavior of a compressed gas depends on the conditions of the compression. If the compression is slow and allows for heat transfer (isothermal), the temperature may remain constant.