As ice is heated it melts, forming a liquid, and then it boils, However, as solid carbon dioxide is heated it goes directly to the vapour state – we say it sublimes – without passing through a liquid state. How could liquid carbon dioxide be produced?

The temperature of the sample does not necessarily rise, when thermal energy (heat) added to a solid or a liquid. Instead, the sample may change from one phase or state to another. Conversion of solid into liquid state is called fusion; conversion of liquid into gases state is called vaporization while conversion of solid directly into gaseous state is called sublimation. But the condensation is a process in which a sample changes its gaseous state to its liquid state. When the temperature of the carbon dioxide gas is lowered below the critical temperature, the gas will condense to its liquid state. Therefore by using the process of condensation, a liquid carbon dioxide could be produced.