Why is there dew on the grass in summer morning?

Because the temperature of water vapor in the air is reduced and liquefied to form small water droplets, the small water droplets stick to the grass to form dewdrops.

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 other gases, such as hydrogen and nitrogen, have very low critical points and must be deeply cooled while pressurized, which is called liquefaction.

Formation mechanism

Liquefaction is the reverse process of vaporization. Gas molecules attract each other and condense into liquid. When a substance is liquefied, it gives off heat. Gases below the critical temperature can be liquefied. Gases with critical temperature higher than or close to room temperature, such as ether, chlorine, ammonia, sulfur dioxide, carbon dioxide and some hydrocarbons, can be liquefied by compression at room temperature. Gases with very low critical temperature, such as oxygen, nitrogen, hydrogen and helium. Before being liquefied by isothermal compression, it must be cooled to below their critical temperature.