If we increase the temperature of a gas beyond a certain limit, it does not remain a gas: it enters a regime where the thermal energy of its constituent particles is so great that the electrostatic forces which ordinarily bind electrons to atomic nuclei are overcome. Instead of a hot gas composed of electrically neutral atoms, we have two co-mingled populations composed of oppositely charged particles – electrons and ionised nuclei. This is a plasma, and it is neither solid, liquid, nor gas.