Transcript: As the temperature of a gas is raised, the microscopic motions of the atoms and molecules increase. As the velocities of the atoms and molecules increase, they collide harder and harder. At a temperature of several thousand Kelvin, the atoms or molecules collide with sufficient energy to liberate electrons from the atoms. This process continues until eventually all electrons have been liberated, and the gas consists of a sea of nuclei with surrounding electrons, all in violent collisions. This is called a plasma. The process of liberating electrons by violent collisions is called ionization. The gas at the surface of the sun is partly ionized, and deeper into the sun, where the temperature is higher, the gas is fully ionized. Most of the gaseous material of the universe in fact, whether in the form of stars or the intergalactic medium, is highly ionized.