What do you think would happen if a solid were exposed to extremely cold temperatures, or if a gas were exposed to extremely hot temperatures?

At high temperature the gas would diffuse out as the pressure increases and at extremely low temperature the solid becomes compact.

Explanation:

The states of matter largely depends on the temperature. Any substance when crosses the threshold temperature its phase changes.

When temperature is low the motion of molecules is also low and internal energy also gets low. Solid have tendency of settling in low energy level and have highly compact molecules. At low temperature the solid would compress as molecules would be highly condensed.

Gas in the nature has its molecules quite far apart in matter. According to Kinetic theory of gases the increase in temperature causes rapid collisions of the gas molecule as the kinetic energy of molecules increases. The greater force of collision would cause increase in pressure of the container and increased diffusion rate.