Prepare a glass of cold water, add a little salt into it, light the common straws one by one, burn them a little, blow them out and put them into the water quickly. After a few seconds, pull out the straw and the water will soon turn into ice. Reason: There are a lot of ammonia nitrate and other substances in the burnt straw, which will absorb a lot of heat and freeze water when dissolved.

This is the phenomenon of liquid supercooling. A liquid whose temperature is below freezing point but still does not solidify or crystallize is called supercooled liquid. Supercooled liquids are unstable. As long as a little crystal of this substance is put in, it can induce crystallization and raise the temperature of supercooled liquid to freezing point. This unstable state, which will change rapidly under small disturbance, is called metastable state. It will freeze quickly. Freezing of water: The freezing of water includes two processes: cooling and crystallization. In the cooling process, the temperature at which stable crystal nuclei begin to form in water or the lowest temperature at which the temperature begins to rise is called supercooling critical temperature or supercooling temperature. The supercooling temperature must be lower than the freezing point, but once the temperature rises to the freezing point, as long as the water continues to freeze and release latent heat, the temperature of the water-ice mixture will remain at 0 degrees Celsius.