Question

At which point could the substance shown exist as a gas or a solid but not a liquid?

Answer 1

Answer:

The substance is not shown, so I'll answer the question in general terms.

Any substance can exist as a gas or a solid but not a liquid below the triple point pressure. As can be seen in the figure attached, below the triple point pressure there are only two possible phases, solid and gas. This means that  a solid at a pressure below the triple point pressure which is heated at constant pressure (only its temperature increase) will sublimate, that is, it transforms into gas without passing through liquid phase. Analogously, a gas at a pressure below the triple point pressure which is cooled at constant pressure (only its temperature decrease) will deposit, that is, it transforms into solid without passing through liquid phase .

Answer 2

If a solid changes into gas state without being a liquid first , this change of state is called sublimation . Iodine solid and solidified carbon dioxide (i.e. dry ice ) are examples of substance that sublime . The opposite process of sublimation is deposition . I.e. When a gas turns into a solid directly . The formation of frost is an example of deposition .