Final answer:
The transition from gas to plasma is called 'ionization', which is the process of gas particles gaining enough energy to become ionized, though there is no one-word term equivalent to 'melting' or 'sublimation' for this phase change.
Step-by-step explanation:
The process of a substance changing from a gas to a plasma state does not have a commonly used one-word equivalent like 'melting' or 'sublimation'. However, the process can be described as ionization when considering that gas particles gain enough energy to strip off electrons, creating ionized particles, and thus entering the plasma state.
The term 'ionization' is indeed the best way to describe this phase change, as it inherently captures the key characteristic of plasma: being a gas-like state composed of charged particles (ions and electrons).