The critical temperature refers to the highest temperature at which a substance changes from the gas phase to the liquid phase. Each substance has a specific temperature above which no matter how the pressure is increased, the gaseous substance will not liquefy. This temperature is the critical temperature. According to the above definition, Which of the following are the changes caused by reaching the critical temperature:. ['popsicles taken out of the refrigerator in the summer emit white gas at room temperature.', 'when cooking, the water will become water vapor when heated above 100 ℃.', 'the helium in the air can be changed into liquid by pressurizing only -268 ℃.', 'natural gas under normal pressure, when cooled to -162 ° C, it changes from gaseous to liquid, which is called liquefied natural gas.']