Question

Which substances do not change their state ?

Answer 1

1. Gases and plasma are the two states that do not change their states on heating.

2. They both utilise the energy gained by increasing the volume.

Gas/Vapours turn to liquid by contracting due to condensation, but on heating their physical state cannot reverse back into solid or liquid.

Hence, a gas on heating will remain a gas itself as it expands.

Furthermore, answer to your question is all gases like oxygen O2, carbon dioxide CO2, Hydrogen H2, N2O , C4H10 , C3H8,Ar ,He ,N2,etc.