Most gases behave like ideal gases at high temperature. For example, the PV curve of CO2 gas at 50 °C is like the ideal Boyle’s law curve. As the temperature is lowered, the PV curve shows a deviation from the ideal Boyle’s law curve. At a particular value of low temperature, the gas gets liquified at certain increased value of pressure. For example, CO2 gas liquifies at 38.98 °C and 73 atmosphere pressure. This is the highest temperature at which liquid CO2 can exist. Above this temperature, liquid CO2 cannot form even if very high pressure is applied. Other gases also show similar behaviour.
