gas vs state of matter

gas and state of matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
gas	Yes	No	Yes	No
state of matter	Yes	No	No	No

As nouns, state of matter is a hypernym of gas; that is, state of matter is a word with a broader meaning than gas:

gas: the state of matter distinguished from the solid and liquid states by: relatively low density and viscosity; relatively great expansion and contraction with changes in pressure and temperature; the ability to diffuse readily; and the spontaneous tendency to become distributed uniformly throughout any container
state of matter: (chemistry) the three traditional states of matter are solids (fixed shape and volume) and liquids (fixed volume and shaped by the container) and gases (filling the container)

Other hypernyms of gas include state.

gas (noun)	state of matter (noun)
a pedal that controls the throttle valve	(chemistry) the three traditional states of matter are solids (fixed shape and volume) and liquids (fixed volume and shaped by the container) and gases (filling the container)
the state of matter distinguished from the solid and liquid states by: relatively low density and viscosity; relatively great expansion and contraction with changes in pressure and temperature; the ability to diffuse readily; and the spontaneous tendency to become distributed uniformly throughout any container
a state of excessive gas in the alimentary canal
a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
a volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines
a fossil fuel in the gaseous state; used for cooking and heating homes

gas (verb)	state of matter (verb)
show off
attack with gas; subject to gas fumes