Which substances do not change their state ?
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.
Give two examples for each of the following :
(a) The substances which sublime.
(b) The substances which do not change their state on heating.
Which of these physical properties do not change when two different substances are used to form a mixture?