Carbon dioxide can be changed to a liquid by cooling it to its boiling point, which is -78.5 degrees Celsius at atmospheric pressure. At this temperature, the carbon dioxide molecules slow down and begin to condense into a liquid. The liquid carbon dioxide is then typically stored in a pressurized container.

Carbon dioxide is also converted to a liquid through the process of gas compression and cooling. This process is commonly known as liquefaction of carbon dioxide. In this method, carbon dioxide gas (CO2) is compressed to a high pressure, typically several atmospheres, to increase its density and reduce its volume. Subsequently, the compressed carbon dioxide gas is cooled using various techniques such as heat exchange, refrigeration, or expansion. By reducing the temperature, the CO2 gas reaches its condensation point, at which it changes into a liquid state.

The primary purpose of converting carbon dioxide to a liquid is for transportation, storage, and industrial uses. Liquid carbon dioxide has a higher density compared to its gaseous form, making it easier to transport and store. It is also commonly used as a cooling agent in refrigeration systems, in the production of carbonated beverages, as an inert gas during welding, in fire extinguishers, and various chemical processes. Additionally, liquid CO2 can be utilized in the food industry for freezing, chilling, and preservation.