"White gas" is floating downward. Because water vapor will liquefy when it meets a cold popsicle, it will form small water droplets, that is, "white gas", which is denser than air, so it moves downward.

Note: Water vapor is liquefied when it is cold to form water droplets, not gas. Liquefaction: exothermic

The "white gas" formed by the liquefaction of extended data is the process of popsicles changing from gas to liquid, which will radiate heat to the outside world. There are two ways to realize liquefaction, one is to reduce the temperature, and the other is to compress the volume. Critical temperature is the highest temperature at which gas can be liquefied.

In reality, some gases (such as ammonia and natural gas) are usually liquefied because the volume of the gas will usually become one thousandth of the original after liquefaction, which is convenient for storage and transportation. Because the critical points of these two gases are very high, they can become liquid when pressurized at room temperature, while the critical points of other gases, such as hydrogen and nitrogen, are very low, so they must be cryogenic while pressurized.

References:

Baidu encyclopedia-white gas