This is a result of the fact that gas molecules move independently of one another and often at high speeds. The molecules of gases exert no attractive or repulsive forces on each other. Gases will diffuse and mix completely with other gases, forming a completely homogenous mixture. The diffusion of gases is much quicker than that of liquids. Gases will also diffuse through solids and liquids.
Gases have special relationships involving their temperatures, volumes, and pressures.
These relationships are so important that they are excluded from this discussion and saved for discussion by themselves in Lesson 11. Under normal conditions matter exists in one of the previous three phases. Also under normal circumstances gases do not conduct electricity. The existence of the ions causes the gas to conduct an electric current. These extreme conditions exist naturally in stars.