Final answer:
Propane is the substance that is a gas at 100°C; water and ethanol would also be gases at this temperature, while table salt would remain solid.
Step-by-step explanation:
The substance that is a gas at 100°C is Propane (C). At 100°C, water (A) is at its boiling point and undergoes a phase transition from liquid to gas. Ethanol (B) has a boiling point of about 78.37°C, so it would also be a gas at 100°C. However, propane (C) is a gas at room temperature and is well above its boiling point at 100°C. Table salt (D) has an extremely high melting point of 801°C and would still be solid at 100°C.
n physics, a state of matter is one of the distinct forms in which matter can exist. Four states of matter are observable in everyday life: solid, liquid, gas, and plasma. Many intermediate states are known to exist, such as liquid crystal, and some states only exist under extreme conditions, such as Bose–Einstein condensates and Fermionic condensates (in extreme cold), neutron-degenerate matter (in extreme density), and quark–gluon plasma (at extremely high energy). For a complete list of all exotic states of matter, see the list of states of matter.